Diet

Older people do seem to be much more vulnerable to deficits in thinking and remembering caused by poor diet.

Low levels of B-12 and folic acid in particular, appear to be involved in age-related cognitive decline.

Green leafy vegetables, citrus fruits and juices, whole wheat bread and dry beans are good sources of folate. Fruit and vegetables, whole grains, beans and other protein sources (nuts, meat, fish) are good sources of the B vitamins.

Experiments with rats suggest sunflower seeds (and other seeds high in linoleic acid) may help against cognitive decline caused by hypertension.

Fruits and vegetables high in antioxidants (for example, spinach, blueberries) may reduce and even reverse age-related impairment to neuron function.

Experiments in rats suggest that two chemicals normally found in the body's cells and available as dietary supplements may also improve memory function and increase energy in older people. One of these substances is found in meat and vegetables, the other in green leafy vegetables.

Carbohydrates, fat, and protein, all seem to have positive effects - different effects - on thinking and remembering. It has been shown that having breakfast has a positive effect on memory in older adults; perhaps low energy intake in general is partly responsible for cognitive decline in some older people.

 

Health news relating to diet

Latest Research News

A small study involving 50 younger adults (18-35; average age 24) has found that those with a higher BMI performed significantly worse on a computerised memory test called the “Treasure Hunt Task”.

The task involved moving food items around complex scenes (e.g., a desert with palm trees), hiding them in various locations, and indicating afterward where and when they had hidden them. The test was designed to disentangle object, location, and temporal order memory, and the ability to integrate those separate bits of information.

Those with higher BMI were poorer at all aspects of this task. There was no difference, however, in reaction times, or time taken at encoding. In other words, they weren't slower, or less careful when they were learning. Analysis of the errors made indicated that the problem was not with spatial memory, but rather with the binding of the various elements into one coherent memory.

The results could suggest that overweight people are less able to vividly relive details of past events. This in turn might make it harder for them to keep track of what they'd eaten, perhaps making overeating more likely.

The 50 participants included 27 with BMI below 25, 24 with BMI 25-30 (overweight), and 8 with BMI over 30 (obese). 72% were female. None were diagnosed diabetics. However, the researchers didn't take other health conditions which often co-occur with obesity, such as hypertension and sleep apnea, into account.

This is a preliminary study only, and further research is needed to validate its findings. However, it's significant in that it adds to growing evidence that the cognitive impairments that accompany obesity are present early in adult life and are not driven by diabetes.

The finding is also consistent with previous research linking obesity with dysfunction of the hippocampus and the frontal lobe.

http://www.eurekalert.org/pub_releases/2016-02/uoc-bol022616.php

https://www.theguardian.com/science/neurophilosophy/2016/mar/03/obesity-linked-to-memory-deficits

[4183] Cheke LG, Simons JS, Clayton NS. Higher body mass index is associated with episodic memory deficits in young adults. The Quarterly Journal of Experimental Psychology [Internet]. 2015 :1 - 12. Available from: http://dx.doi.org/10.1080/17470218.2015.1099163

Another study adds to the growing evidence that a Mediterranean diet is good for the aging brain.

The New York study used data from 674 non-demented older adults (average age 80). It found that those who closely followed such a diet showed significantly less brain shrinkage. Specifically, total brain volume was an average 13.11 milliliters greater, with grey matter volume 5 millilitres greater, and white matter 6.4 millilitres greater.

Eating at least five of the recommended Mediterranean diet components was associated with benefits equivalent to five years of age. By far the most important of these components was regular fish and reduced meat intake — at least 3 to 5 ounces of fish weekly; no more than 3.5 ounces of meat daily.

This is consistent with a considerable amount of research indicating the benefits of fish in fighting age-related cognitive decline.

http://www.theguardian.com/lifeandstyle/2015/oct/21/mediterranean-diet-may-slow-the-ageing-process-by-five-years

A two-year study which involved metabolic testing of 50 people, suggests that Alzheimer's disease consists of three distinct subtypes, each one of which may need to be treated differently. The finding may help explain why it has been so hard to find effective treatments for the disease.

The subtypes are:

  • Inflammatory, in which markers such as C-reactive protein and serum albumin to globulin ratios are increased.
  • Non-inflammatory, in which these markers are not increased but other metabolic abnormalities (such as insulin resistance, hypovitaminosis D, and hyper-homocysteinemia) are present. This tends to affect slightly older individuals than the first subtype: 80s rather than 70s.
  • Cortical, which affects relatively young individuals (typically 50s- early 70s) and appears more widely distributed across the brain than the other subtypes, showing widespread cortical atrophy rather than marked hippocampal atrophy. It typically presents with language and number difficulties first, rather than memory loss. Typically, there is an impaired ability to hold onto a train of thought. It is often misdiagnosed, typically affects people without a family history of Alzheimer's, who do not have an Alzheimer's-related gene, and is associated with a significant zinc deficiency (Zinc is implicated in multiple Alzheimer's-related metabolic processes, such as insulin resistance, chronic inflammation, ADAM10 proteolytic activity, and hormonal signaling. Zinc deficiency is relatively common, and associated with increasing age.).

The cortical subtype appears to be fundamentally a different condition than the other two.

I note a study I reported on last year, that found different molecular structures of amyloid-beta fibrils in the brains of Alzheimer's patients with different clinical histories and degrees of brain damage. That was a very small study, indicative only. However, I do wonder if there's any connection between these two findings. At the least, I think this approach a promising one.

The idea that there are different types of Alzheimer's disease is of course consistent with the research showing a variety of genetic risk factors, and an earlier study indicating at least two pathways to Alzheimer's.

It's also worth noting that the present study built on an earlier study, which showed that a program of lifestyle, exercise and diet changes designed to improve the body's metabolism reversed cognitive decline within 3-6 months in nine out of 10 patients with early Alzheimer's disease or its precursors. Note that this was a very small pilot program, and needs a proper clinical trial. Nevertheless, it is certainly very interesting.

http://www.eurekalert.org/pub_releases/2015-09/uoc--adc091615.php

Bredesen, D.E. 2015. Metabolic profiling distinguishes three subtypes of Alzheimer's disease. AGING, 7 (8), 595-600. Full text at http://www.impactaging.com/papers/v7/n8/full/100801.html

Bredesen, D.E. 2014. Reversal of cognitive decline: A novel therapeutic program. AGING, Vol 6, No 9 , pp 707-717. Full text at http://www.impactaging.com/papers/v6/n9/full/100690.html

More evidence for the benefits of the Mediterranean diet for fighting age-related cognitive decline comes from a large 5-year study. The study involved 960 older adults, whose cognitive change was assessed over 4.7 years. Those who followed the MIND diet more rigorously showed an equivalent of being 7.5 years younger cognitively than those who followed the diet least.

The Mediterranean-DASH Diet Intervention for Neurodegenerative Delay is a hybrid of the Mediterranean and DASH (Dietary Approaches to Stop Hypertension) diets. It requires at least:

  • three servings of whole grains every day
  • a green leafy vegetable and one other vegetable every day
  • a glass of wine
  • snack most days on nuts
  • beans every other day or so
  • poultry at least twice a week
  • fish at least once a week
  • berries at least twice a week (blueberries are particularly recommended)
  • very limited intake of designated unhealthy foods, especially:
    • butter
    • sweets and pastries
    • whole fat cheese
    • fried or fast food

http://www.eurekalert.org/pub_releases/2015-08/rumc-eaa080415.php

http://www.theguardian.com/society/2015/aug/05/diet-high-in-leafy-green-vegetables-may-slow-cognitive-decline-in-elderly-study

Glucose levels linked to cognitive decline in those with MCI

A study involving 264 older adults with mild cognitive impairment has found that those with normal glucose levels (167; 63%) had less cognitive decline over 2 years than those with impaired (high) glucose levels (97; 37%). They also showed less brain shrinkage and were less likely to develop Alzheimer’s. The fasting glucose levels were classified according to the American Diabetes criteria.

[3614] Vos SJB, Xiong C, Visser PJ, Jasielec MS, Hassenstab J, Grant EA, Cairns NJ, Morris JC, Holtzman DM, Fagan AM. Preclinical Alzheimer's disease and its outcome: a longitudinal cohort study. The Lancet Neurology [Internet]. 2013 ;12(10):957 - 965. Available from: http://www.thelancet.com/journals/laneur/article/PIIS1474-4422(13)70194-7/abstract

Rat study suggests cognitive decline in diabetics related to amyloid-beta buildup

A rat study supports the growing evidence of a link between type 2 diabetes and Alzheimer’s. In this study, 20 rats were fed a high-fat diet to give them type 2 diabetes. A subsequent test found that the diabetic rats had significantly poorer memories than the control group of rats on a healthy diet (the rats were taught to associate a dark cage with an electric shock; how long the rat continues to remember that the stimulus means a shock — as shown by their frozen reaction — is taken as a measure of how good their memory is; the diabetic rats froze for less than half the time of the controls).

The diabetic rats then had their brains (specifically, the hippocampus) injected with antibodies that disrupt amyloid-beta plaques. This produced no change in their behavior. However, when they were given antibodies that disrupt amyloid-beta oligomers (precursors of the plaques), the memory deficit was reversed, and they behaved the same as the healthy rats.

These findings suggest that the cognitive decline often seen in type 2 diabetes is not due to the disruption in insulin signaling, as thought, but rather the build-up of amyloid oligomers. Previous research has shown that the same enzymes break down both insulin and the oligomers, so when there’s a lot of insulin (which the enzymes prioritize), the enzymes don’t have as much opportunity to work on breaking down the oligomers. The oligomers collect, preventing the insulin from reaching their proper receptors in the hippocampus, which impairs cognitive function.

All this supports the idea that type 2 diabetes may be thought of as early-stage Alzheimer's. Obviously a lot more work needs to be done to confirm this picture, but certainly in the mean time, it can be taken as another reason to take type 2 diabetes very seriously.

www.newscientist.com/article/mg22029453.400-are-alzheimers-and-diabetes-the-same-disease.html

McNay, E.C., Osborne, D., et al. 2014. Preliminary data presented at the Society for Neuroscience meeting in San Diego in November, 2013

High blood sugar makes Alzheimer’s plaque more toxic

A study of cell cultures taken from rodents’ cerebral blood vessels has found that, while cells exposed to either high glucose or amyloid-beta showed no changes in viability, exposure to both decreased cell viability by 40%. Moreover, cells from diabetic mice were more vulnerable to amyloid-beta, even at normal glucose levels.

The findings support evidence pointing to high glucose as a risk factor for vascular damage associated with Alzheimer’s, and adds weight to the view that controlling blood sugar levels is vital for those with diabetes.

http://www.futurity.org/high-blood-sugar-makes-alzheimers-plaque-toxic/

[3558] Carvalho C, Katz PS, Dutta S, Katakam PVG, Moreira PI, Busija DW. Increased Susceptibility to Amyloid-β Toxicity in Rat Brain Microvascular Endothelial Cells under Hyperglycemic Conditions. Journal of Alzheimer's Disease [Internet]. 2014 ;38(1):75 - 83. Available from: http://dx.doi.org/10.3233/JAD-130464

Mechanism by which diabetes increases Alzheimer's risk revealed

Although it's well-established now that diabetes is a major risk factor for dementia, the reason is still not well understood. To test the hypothesis that epigenetic changes in the brain, affecting synaptic function, may be part of the reason, the brains of diabetics and others were examined post-mortem. Diabetics' brains were found to have significantly higher expression of a class of molecules (histone deacetylases class IIa) and this was associated with impaired expression of synaptic proteins.

This finding was confirmed in mice genetically engineered to develop an Alzheimer’s-type condition, who were induced to develop diabetes. The increase of HDAC IIa was associated with synaptic impairments in the hippocampus, through the work of amyloid oligomers.

Some 60% of Alzheimer's patients have at least one serious medical condition associated with diabetes.

http://www.eurekalert.org/pub_releases/2013-10/tmsh-cie102213.php

[3615] Wang J, Gong B, Zhao W, Tang C, Varghese M, Nguyen T, Bi W, Bilski A, Begum S, Vempati P, et al. Epigenetic Mechanisms Linking Diabetes and Synaptic Impairments. Diabetes [Internet]. 2014 ;63(2):645 - 654. Available from: http://diabetes.diabetesjournals.org/content/63/2/645

High Blood Sugar Linked to Dementia

A seven-year study involving 2,067 older adults (average age 76 at start) has found that those with a high blood glucose level, whether or not they had diabetes, were more likely to develop dementia. Moreover, this was a linear relationship — meaning that the risk steadily increased with higher glucose levels, and decreased the lower it was. Thus, even those with ‘normal’ glucose levels were subject to this relationship, with those whose blood sugar averaged 115 milligrams per deciliter, having an 18% higher risk of dementia than those at 100 mg/dL. Other risk factors, such as high blood pressure, smoking, exercise, and education, were taken into account in the analysis.

The findings add weight to the idea that the brain is a target organ for damage by high blood sugar.

Over the course of the study, a quarter (524) developed dementia of some kind, primarily Alzheimer’s disease or vascular dementia. At the beginning of the study, 232 (11%) had diabetes, and a further 111 developed it by the end of the study. Nearly a third (32%) of those with diabetes at the beginning of the study developed dementia, compared to just under a quarter of those without (24.5%).

http://newoldage.blogs.nytimes.com/2013/08/09/high-blood-sugar-linked-to-dementia/

The journal article is freely available at http://www.nejm.org/doi/full/10.1056/NEJMoa1215740#t=article

[3563] Crane PK, Walker R, Hubbard RA, Li G, Nathan DM, Zheng H, Haneuse S, Craft S, Montine TJ, Kahn SE, et al. Glucose Levels and Risk of Dementia. New England Journal of Medicine [Internet]. 2013 ;369(6):540 - 548. Available from: http://www.nejm.org/doi/full/10.1056/NEJMoa1215740

Undiagnosed pre-diabetes highly prevalent in early Alzheimer's disease

A study involving 128 patients with mild to moderate Alzheimer’s disease, which had specifically excluded those with known diabetes, found that 13% of them did in fact have diabetes, and a further 30% showed glucose intolerance, a pre-diabetic condition.

Turner presented his findings at the Alzheimer's Association International Congress in Boston on July 14.

http://www.eurekalert.org/pub_releases/2013-07/gumc-uph070513.php

Association between hypoglycemia, dementia in older adults with diabetes

A 12-year study involving 783 older adults with diabetes (average age 74) has found that 148 (19%) developed dementia. Those 61 patients (8%) who had a reported hypoglycemic event were twice as likely to develop dementia compared to those who didn’t suffer such an event (34% vs. 17%). Similarly, those with dementia were more likely to experience a severe hypoglycemic event.

The findings suggest some patients risk entering a downward spiral in which hypoglycemia and cognitive impairment fuel one another, leading to worse health

http://www.eurekalert.org/pub_releases/2013-06/tjnj-abh060613.php

http://www.eurekalert.org/pub_releases/2013-06/uoc--aal060613.php

[3622] Yaffe K, CM F, N H, et al. ASsociation between hypoglycemia and dementia in a biracial cohort of older adults with diabetes mellitus. JAMA Internal Medicine [Internet]. 2013 ;173(14):1300 - 1306. Available from: http://dx.doi.org/10.1001/jamainternmed.2013.6176

Dementia risk greatest for older Native-Americans and African-Americans with diabetes

In the first study to look at racial and ethnic differences in dementia risk among older adults with type 2 diabetes, Native Americans were 64% more likely to develop dementia than Asian-Americans, and African-Americans were 44% more likely. Asian-Americans had the lowest risk, and non-Hispanic whites and Latinos were intermediate.

The study involved 22,171 older adults (60+), of whom 3,796 patients (17%) developed dementia over the 10 years of the study. Almost 20% of the African-Americans and Native Americans developed dementia.

The ethnic differences were not explained by diabetes-related complications, glycemic control or duration of diabetes, or neighborhood deprivation index, body mass index, or hypertension.

http://www.eurekalert.org/pub_releases/2013-12/kp-drg121113.php

[3590] Mayeda ER, Karter AJ, Huang ES, Moffet HH, Haan MN, Whitmer RA. Racial/Ethnic Differences in Dementia Risk Among Older Type 2 Diabetic Patients: The Diabetes and Aging Study. Diabetes Care [Internet]. 2014 ;37(4):1009 - 1015. Available from: http://care.diabetesjournals.org/content/37/4/1009

Data from the population-based Finnish Cardiovascular Risk Factors, Aging and Incidence of Dementia (CAIDE) study has revealed that healthy dietary choices in midlife may prevent dementia in later years. Out of 2,000 participants, 1,449 took part in the follow-up. The participants were 39 to 64 years old at baseline and 65 to 75 years old at follow-up.

Those who ate the healthiest diet at around age 50 had an almost 90% lower risk of dementia in a 14-year follow-up study than those whose diet was the least healthy.

Healthy foods included vegetables, berries and fruits, fish and unsaturated fats from milk products and spreads; unhealthy foods included sausages, eggs, sweets, sugary drinks, salty fish and saturated fats from milk products and spreads.

Consistent with other research, a high intake of saturated fats was also linked to poorer cognition and an increased risk of mild cognitive impairment 21 years later. A higher saturated fat intake was also associated with an increased risk of dementia among those carrying the “Alzheimer's gene”, ApoE4.

Those consuming 3 to 5 cups of coffee daily had a smaller risk of dementia than those consuming less or more.

http://www.eurekalert.org/pub_releases/2014-03/uoef-hmd031014.php

Eskelinen, Marjo: The effects of midlife diet on late-life cognition: an epidemiological approach. Publications of the University of Eastern Finland. Dissertations in Health Sciences., no 220. http://epublications.uef.fi/pub/urn_isbn_978-952-61-1394-4/

Eskelinen MH, Ngandu T, Helkala E-L, Tuomilehto J, Nissinen A, Soininen H, Kivipelto M. Fat intake at midlife and cognitive impairment later in life: a population-based CAIDE study. Int J Geriatr Psychiatry 23(7): 741, 2008.

Laitinen MH, Ngandu T, Rovio S, Helkala E-L, Uusitalo U, Viitanen M, Nissinen A, Tuomilehto J, Soininen H, Kivipelto M. Fat Intake at Midlife and Risk of Dementia and Alzheimer's Disease: A Population-Based Study. Dement Geriatr Cogn Disord 22(1): 99, 2006.

Eskelinen MH, Ngandu T, Tuomilehto J, Soininen H, Kivipelto M. Midlife Coffee and Tea Drinking and the Risk of Late-Life Dementia: A Population-based CAIDE Study. J Alzheimers Dis 16(1): 85-91, 2009.

Eskelinen MH, Ngandu T, Tuomilehto J, Soininen H, Kivipelto M. Midlife Healthy Diet Index and Late-Life Dementia and Alzheimer's Disease. Dement Geriatr Cogn Disord Extra 1(1): 103-112, 2011.

Following on from the evidence that Alzheimer’s brains show higher levels of metals such as iron, copper, and zinc, a mouse study has found that amyloid plaques in Alzheimer’s-like brains with significant neurodegeneration have about 25% more copper than those with little neurodegeneration. This is consistent with a human study showing very high levels of copper in Alzheimer’s plaques.

Iron, though doubled in Alzheimer’s brains compared to controls, was not significantly different as a function of neurodegeneration, and zinc showed very little difference.

The findings suggest that the cellular control of copper is altered in some way in Alzheimer’s brains, while the increase in oxidized iron suggests it might be useful as a biomarker for the early diagnosis of Alzheimer’s.

http://www.eurekalert.org/pub_releases/2013-08/ip-elo082113.php

[3555] Bourassa MW, Leskovjan AC, Tappero RV, Farquhar ER, Colton CA, Van Nostrand WE, Miller LM. Elevated copper in the amyloid plaques and iron in the cortex are observed in mouse models of Alzheimer's disease that exhibit neurodegeneration. Biomedical Spectroscopy and Imaging [Internet]. 2013 ;2(2):129 - 139. Available from: http://dx.doi.org/10.3233/BSI-130041

A study involving 74 older adults (70+), of whom 3 had mild dementia, 33 were cognitively normal and 38 had mild cognitive impairment, has found that high levels of "good" cholesterol and low levels of "bad" cholesterol correlated with lower levels of the amyloid-beta plaques in the brain (a hallmark of Alzheimer's disease).

http://www.eurekalert.org/pub_releases/2013-12/uoc--hga122613.php

In a large Mayo Clinic study, self-reported diet was found to be significantly associated with the risk of seniors developing mild cognitive impairment or dementia over a four-year period.

The study involved 1,230 older adults (70-89) who completed a 128-item food-frequency questionnaire about their diet during the previous year. Of these, around three-quarters (937) showed no signs of cognitive impairment at the beginning of the study period, and were asked to return for follow-up cognitive assessments. These assessments took place every 15 months. After about four years, 200 (21%) had developed mild cognitive impairment (MCI) or dementia.

The likelihood of cognitive deterioration was significantly affected by the type of diet. Those with the highest carbohydrate intake were nearly twice as likely to develop cognitive impairment compared to those with the lowest carbohydrate consumption, and when total fat and protein intake were taken into account, they were 3.6 times likelier to develop impairment.

Those with the highest sugar intake were 1.5 times more likely to develop cognitive impairment.

But — a finding that will no doubt surprise many — those with the highest fat consumption were 42% less likely to develop cognitive impairment, compared to those with the lowest level of fats.

Less surprisingly, those with highest intake of protein had a reduced risk of 21%.

In other words, the worst diet you can have, if you want to keep your brain healthy, is one that receives most of its calories from carbohydrates and sugar, and relatively little from fats and protein.

The findings about carbs, sugar, and protein are consistent with other research. The finding regarding fats is somewhat more surprising. The inconsistency may lie in the type of fat. Research implicating high-fat diets as a risk factor in Alzheimer’s have used saturated fats. Diets high in olive oil, on the other hand, have been found to be beneficial.

It seems likely that the danger of carbs and too much sugar lies in the effects on glucose and insulin metabolism. Saturated fats also interfere with glucose metabolism. Alzheimer’s has sometimes been called Type 3 diabetes, because of its association with insulin problems.

Roberts RO, Roberts LA, Geda YE, Cha RH, Pankratz VS, O'Connor HM, Knopman DS, Petersen RC. 2012. Relative intake of macronutrients impacts risk of mild cognitive impairment or dementia. Journal of Alzheimers Disease, 32(2), 329-39.

Green tea is thought to have wide-ranging health benefits, especially in the prevention of cardiovascular disease, inflammatory diseases, and diabetes. These are all implicated in the development of age-related cognitive impairment, so it’s no surprise that regular drinking of green tea has been suggested as one way to help protect against age-related cognitive decline and dementia. A new mouse study adds to that evidence by showing how a particular compound in green tea promotes neurogenesis.

The chemical EGCG, (epigallocatechin-3 gallate) is a known anti-oxidant, but this study shows that it also has a specific benefit in increasing the production of neural progenitor cells. Like stem cells, these progenitor cells can become different types of cell.

Mice treated with EGCG displayed better object recognition and spatial memory than control mice, and this improved performance was associated with the number of progenitor cells in the dentate gyrus and increased activity in the sonic hedgehog signaling pathway (confirming the importance of this pathway in adult neurogenesis in the hippocampus).

The findings add to evidence that green tea may help protect against cognitive impairment and dementia.

I’ve reported before on the growing evidence that metabolic syndrome in middle and old age is linked to greater risk of cognitive impairment in old age and faster decline. A new study shows at least part of the reason.

The study involved 71 middle-aged people recruited from the Wisconsin Registry for Alzheimer's Prevention (WRAP), of whom 29 met the criteria for metabolic syndrome (multiple cardiovascular and diabetes risk factors including abdominal obesity, high blood pressure, high blood sugar and high cholesterol).

Those with metabolic syndrome averaged 15% less blood flow to the brain than those without the syndrome.

One tried and true method of increasing blood flow to the brain is of course through exercise.

The study was presented at the Alzheimer's Association International Conference in Vancouver, Canada by Barbara Bendlin.

HIV-associated dementia occurs in around 30% of untreated HIV-positive patients. Surprisingly, it also is occasionally found in some patients (2-3%) who are being successfully treated for HIV (and show no signs of AIDS).

A new study may have the answer for this mystery, and suggest a solution. Moreover, the answer may have general implications for those experiencing cognitive decline in old age.

The study found that HIV, although it doesn’t directly infect neurons, tries to stop the development of BDNF. Long known to be crucial for memory and learning, the reduced production of mature BDNF results in axons and dendrites shortening — meaning connections between neurons are lost. That in turn, brings about the death of some neurons.

It seems that the virus interferes with the normal process of development in BDNF, whereby one form of it, called proBDNF, is cut by certain enzymes into a new form called mature BDNF. It is in this form that it has its beneficial effect on neuron growth. Unfortunately, in its earlier form it is toxic to neurons.

This imbalance in the proportions of mature BDNF and proBDNF also appears to occur as we age, and in depression. It may also be a risk factor in Parkinson's and Huntington's diseases.

However, these findings suggest a new therapeutic approach.

Compounds in green tea and chocolate may help protect brain cells

In which context, it is interesting to note another new study, which has been busy analyzing the effects on brain cells of 2000 compounds, both natural and synthetic. Of the 256 that looked to have protective effects, nine were related to epicatechin, which is found in cocoa and green tea leaves.

While we’ve been aware for some time of these positive qualities, the study specifically identified epicatechin and epigallocatechin gallate (EGCG) as being the most effective at helping protect neurons by inducing production of BDNF.

One of the big advantages these compounds have is in their ability to cross the blood-brain barrier, making them a good candidate for therapy.

While green tea, dark chocolate, and cocoa are particularly good sources, many fruits also have good levels, in particular, black grapes, blackberries, apples, cherries, pears, and raspberries. (see this University of Davis document (pdf) for more detail)

Back in 2009, I reported briefly on a large Norwegian study that found that older adults who consumed chocolate, wine, and tea performed significantly better on cognitive tests. The association was assumed to be linked to the flavanols in these products. A new study confirms this finding, and extends it to older adults with mild cognitive impairment.

The study involved 90 older adults with MCI, who consumed either 990 milligrams, 520 mg, or 45 mg of a dairy-based cocoa drink daily for eight weeks. Their diet was restricted to eliminate other sources of flavanols (such as tea, red wine, apples and grapes).

Cognitive assessment at the end of this period revealed that, although scores on the MMSE were similar across all groups, those consuming higher levels of flavanol cocoa took significantly less time to complete Trail Making Tests A and B, and scored significantly higher on the verbal fluency test. Insulin resistance and blood pressure was also lower.

Those with the highest levels of flavanols did better than those on intermediate levels on the cognitive tests. Both did better than those on the lowest levels.

Changes in insulin resistance explained part, but not all, of the cognitive improvement.

One caveat: the group were generally in good health without known cardiovascular disease — thus, not completely representative of all those with MCI.

 

A study designed to compare the relative benefits of exercise and diet control on Alzheimer’s pathology and cognitive performance has revealed that while both are beneficial, exercise is of greater benefit in reducing Alzheimer’s pathology and cognitive impairment.

The study involved mice genetically engineered with a mutation in the APP gene (a familial risk factor for Alzheimer’s), who were given either a standard diet or a high-fat diet (60% fat, 20% carbohydrate, 20% protein vs 10% fat, 70% carbohydrate, 20% protein) for 20 weeks (from 2-3 to 7-8 months of age). Some of the mice on the high-fat diet spent the second half of that 20 weeks in an environmentally enriched cage (more than twice as large as the standard cage, and supplied with a running wheel and other objects). Others on the high-fat diet were put back on a standard diet in the second 10 weeks. Yet another group were put on a standard diet and given an enriched cage in the second 10 weeks.

Unsurprisingly, those on the high-fat diet gained significantly more weight than those on the standard diet, and exercise reduced that gain — but not as much as diet control (i.e., returning to a standard diet) did. Interestingly, this was not the result of changes in food intake, which either stayed the same or slightly increased.

More importantly, exercise and diet control were roughly equal in reversing glucose intolerance, but exercise was more effective than diet control in ameliorating cognitive impairment. Similarly, while amyloid-beta pathology was significantly reduced in both exercise and diet-control conditions, exercise produced the greater reduction in amyloid-beta deposits and level of amyloid-beta oligomers.

It seems that diet control improves metabolic disorders induced by a high-fat diet — conditions such as obesity, hyperinsulinemia and hypercholesterolemia — which affects the production of amyloid-beta. However exercise is more effective in tackling brain pathology directly implicated in dementia and cognitive decline, because it strengthens the activity of an enzyme that decreases the level of amyloid-beta.

Interestingly, and somewhat surprisingly, the combination of exercise and diet control did not have a significantly better effect than exercise alone.

The finding adds to the growing pile of evidence for the value of exercise in maintaining a healthy brain in later life, and helps explain why. Of course, as I’ve discussed on several occasions, we already know other mechanisms by which exercise improves cognition, such as boosting neurogenesis.

A rat study has shown how a diet high in fructose (from corn syrup, not the natural levels that occur in fruit) impairs brain connections and hurts memory and learning — and how omega-3 fatty acids can reduce the damage.

We know that these unnaturally high levels of fructose can hurt the brain indirectly through their role in diabetes and obesity, but this new study demonstrates that it also damages the brain directly.

In the study, two groups of rats consumed a fructose solution as drinking water for six weeks. One of these groups also received omega-3 fatty acids in the form of flaxseed oil and DHA. Both groups trained on a maze twice daily for five days before starting the experimental diet. After the six weeks of the diet, the rats were put in the maze again.

Those who didn’t receive the omega-3 oils navigated the maze much more slowly than the second group, and their brains showed a decline in synaptic activity. They also showed signs of resistance to insulin. Indications were that insulin had lost much of its power to regulate synaptic function.

It’s suggested that too much fructose could block insulin's ability to regulate how cells use and store sugar for the energy required for processing information.

It’s estimated that the average American consumes more than 40 pounds of high-fructose corn syrup per year.

The findings are consistent with research showing an association between metabolic syndrome and poorer cognitive function, and help explain the mechanism. They also support the consumption of omega-3 fatty acids as a preventative or ameliorative strategy.

Data from the Women's Health Study, involving 6,183 older women (65+), has found that it isn’t the amount of fat but the type of fat that is associated with cognitive decline. The women were given three cognitive function tests at two-yearly intervals, and filled out very detailed food frequency surveys at the beginning of the study.

Women who consumed the highest amounts of saturated fat (such as that from animals) had significantly poorer cognitive function compared to those who consumed the lowest amounts. Women who instead had a high intake of monounsaturated fats (such as olive oil) had better cognitive scores over time. Total fat, polyunsaturated fat, and trans fat, were not associated with cognitive performance.

The findings are consistent with research associating the Mediterranean diet (high in olive oil) with lower Alzheimer’s risk, and studies linking diets high in saturated fats with greater cognitive decline.

I have reported often on studies pointing to obesity as increasing your risk of developing dementia, and on the smaller evidence that calorie restriction may help fight age-related cognitive decline and dementia (and help you live longer). A new mouse study helps explain why eating less might help the brain.

It turns out that a molecule called CREB-1 is triggered by calorie restriction (defined as only 70% of normal consumption). cAMP Response Element Binding (CREB) protein is an essential component of long-term memory formation, and abnormalities in the expression of CREB have been reported in the brains of Alzheimer’s patients. Restoring CREB to Alzheimer’s mice has been shown to improve learning and memory impairment.

Animal models have also indicated a role for CREB in the improvements in learning and memory brought about by physical exercise. CREB seems to be vital for adult neurogenesis.

The current study found that, when CREB1 was missing (in mice genetically engineered to lack this molecule), calorie restriction had no cognitive benefits. CREB deficiency in turn drastically reduced the expression of Sirt-1. These proteins have been implicated in cardiac function, DNA repair and genomic stability (hence the connection to longevity). More recently, Sirt-1 has also been found to modulate synaptic plasticity and memory formation — an effect mediated by CREB. This role in regulating normal brain function appears to be quite separate from its cell survival functions.

The findings identify a target for drugs that could produce the same cognitive (and longevity) benefits without the need for such strict food reduction.

Reducing your eating and drinking to 70% of normal intake is a severe reduction. Recently, researchers at the National Institute on Ageing in Baltimore have suggested that the best way to cut calories to achieve cognitive benefits was to virtually fast (down to around 500 calories) for two days a week, while eating as much as you want on the other days. Their animal experiments indicate that timing is a crucial element if cognitive benefits are to accrue.

Another preliminary report, this time from the long-running Mayo Clinic study of aging, adds to the evidence that lower consumption reduces the risk of serious cognitive impairment. The first analysis of data has revealed that the risk of developing mild cognitive impairment more than doubled for those in the highest food consumption group (daily calorie consumption between 2,143 and 6,000) compared to those in the lowest (between 600 and 1,526 calories).

Calorie consumption was taken from food questionnaires in which respondents described their diets over the previous year, so must be taken with a grain of salt. Additionally, the analysis didn’t take into account types of food and beverages, or other lifestyle factors, such as exercise. Further analysis will investigate these matters in more depth.

The study involved 1,233 older adults, aged 70 to 89. Of these, 163 were found to have MCI.

None of this should be taken as a recommendation for severely restricting your diet. Certainly such behavior should not be undertaken without the approval of your doctor, but in any case, calorie restriction is only part of a much more complex issue concerning diet. I look forward to hearing more from the Mayo Clinic study regarding types of foods and interacting factors.

[2681] Fusco S, Ripoli C, Podda MV, Ranieri SC, Leone L, Toietta G, McBurney MW, Schütz G, Riccio A, Grassi C, et al. A role for neuronal cAMP responsive-element binding (CREB)-1 in brain responses to calorie restriction. Proceedings of the National Academy of Sciences [Internet]. 2012 ;109(2):621 - 626. Available from: http://www.pnas.org/content/109/2/621.abstract

The findings from the National Institute on Aging were presented at the annual meeting of the American Association for the Advancement of Science in Vancouver.

Geda, Y., Ragossnig, M., Roberts, L.K., Roberts, R., Pankratz, V., Christianson, T., Mielke, M., Boeve, B., Tangalos, E. & Petersen, R. 2012. Caloric Intake, Aging, and Mild Cognitive Impairment: A Population-Based Study. To be presented April 25 at the American Academy of Neurology's 64th Annual Meeting in New Orleans.

The study involved 104 healthy older adults (average age 87) participating in the Oregon Brain Aging Study. Analysis of the nutrient biomarkers in their blood revealed that those with diets high in omega 3 fatty acids and in vitamins C, D, E and the B vitamins had higher scores on cognitive tests than people with diets low in those nutrients, while those with diets high in trans fats were more likely to score more poorly on cognitive tests.

These were dose-dependent, with each standard deviation increase in the vitamin BCDE score ssociated with a 0.28 SD increase in global cognitive score, and each SD increase in the trans fat score associated with a 0.30 SD decrease in global cognitive score.

Trans fats are primarily found in packaged, fast, fried and frozen food, baked goods and margarine spreads.

Brain scans of 42 of the participants found that those with diets high in vitamins BCDE and omega 3 fatty acids were also less likely to have the brain shrinkage associated with Alzheimer's, while those with high trans fats were more likely to show such brain atrophy.

Those with higher omega-3 scores also had fewer white matter hyperintensities. However, this association became weaker once depression and hypertension were taken into account.

Overall, the participants had good nutritional status, but 7% were deficient in vitamin B12 (I’m surprised it’s so low, but bear in mind that these are already a select group, being healthy at such an advanced age) and 25% were deficient in vitamin D.

The nutrient biomarkers accounted for 17% of the variation in cognitive performance, while age, education, APOE genotype (presence or absence of the ‘Alzheimer’s gene’), depression and high blood pressure together accounted for 46%. Diet was more important for brain atrophy: here, the nutrient biomarkers accounted for 37% of the variation, while the other factors accounted for 40% (meaning that diet was nearly as important as all these other factors combined!).

The findings add to the growing evidence that diet has a significant role in determining whether or not, and when, you develop Alzheimer’s disease.

Why is diabetes associated with cognitive impairment and even dementia in older adults? New research pinpoints two molecules that trigger a cascade of events that end in poor blood flow and brain atrophy.

The study involved 147 older adults (average age 65), of whom 71 had type 2 diabetes and had been taking medication to manage it for at least five years. Brain scans showed that the diabetic patients had greater blood vessel constriction than the age- and sex-matched controls, and more brain atrophy. The reduction in brain tissue was most marked in the grey matter in the parietal and occipital lobes and cerebellum. Research has found that, at this age, while the average brain shrinks by about 1% annually, a diabetic brain might shrink by as much as 15%. Diabetics also had more white matter hyperintensities in the temporal, parietal and occipital lobes.

Behaviorally, the diabetics also had greater depression, slower walking, and executive dysfunction.

The reduced performance of blood vessels (greater vasoconstriction, blunted vasodilatation), and increased brain atrophy in the frontal, temporal, and parietal lobes, was associated with two adhesion molecules – sVCAM and sICAM. White matter hyperintensities were not associated with the adhesion molecules, inflammatory markers, or blood vessel changes.

It seems that the release of these molecules, probably brought about by chronic hyperglycemia and insulin resistance, produces chronic inflammation, which in turn brings about constricted blood vessels, reduced blood flow, and finally loss of neurons. The blood vessel constriction and the brain atrophy were also linked to higher glucose levels.

The findings suggest that these adhesion molecules provide two biomarkers of vascular health that could enable clinicians to recognize impending brain damage, that could then perhaps be prevented.

The findings also add weight to the growing evidence that diabetes management is crucial in preventing cognitive decline.

In the last five years, three studies have linked lower neighborhood socioeconomic status to lower cognitive function in older adults. Neighborhood has also been linked to self-rated health, cardiovascular disease, and mortality. Such links between health and neighborhood may come about through exposure to pollutants or other environmental stressors, access to alcohol and cigarettes, barriers to physical activity, reduced social support, and reduced access to good health and social services.

Data from the large Women’s Health Initiative Memory Study has now been analyzed to assess whether the relationship between neighborhood socioeconomic status can be explained by various risk and protective factors for poor cognitive function.

Results confirmed that higher neighborhood socioeconomic status was associated with higher cognitive function, even after individual factors such as age, ethnicity, income, education, and marital status have been taken into account. A good deal of this was explained by vascular factors (coronary heart disease, diabetes, stroke, hypertension), health behaviors (amount of alcohol consumed, smoking, physical activity), and psychosocial factors (depression, social support). Nevertheless, the association was still (barely) significant after these factors were taken account of, suggesting some other factors may also be involved. Potential factors include cognitive activity, diet, and access to health services.

In contradiction of earlier research, the association appeared to be stronger among younger women. Consistent with other research, the association was stronger for non-White women.

Data from 7,479 older women (65-81) was included in the analysis. Cognitive function was assessed by the Modified MMSE (3MSE). Neighborhood socioeconomic status was assessed on the basis of: percentage of adults over 25 with less than a high school education, percentage of male unemployment, percentage of households below the poverty line, percentage of households receiving public assistance, percentage of female-headed households with children, and median household income. Around 87% of participants were White, 7% Black, 3% Hispanic, and 3% other. Some 92% had graduated high school, and around 70% had at least some college.

[2523] Shih RA, Ghosh-Dastidar B, Margolis KL, Slaughter ME, Jewell A, Bird CE, Eibner C, Denburg NL, Ockene J, Messina CR, et al. Neighborhood Socioeconomic Status and Cognitive Function in Women. Am J Public Health [Internet]. 2011 ;101(9):1721 - 1728. Available from: http://ajph.aphapublications.org/cgi/content/abstract/101/9/1721

Previous:

Lang IA, Llewellyn DJ, Langa KM, Wallace RB, Huppert FA, Melzer D. 2008. Neighborhood deprivation, individual socioeconomic status, and cognitive function in older people: analyses from the English Longitudinal Study of Ageing. J Am Geriatr Soc., 56(2), 191-198.

Sheffield KM, Peek MK. 2009. Neighborhood context and cognitive decline in older Mexican Americans: results from the Hispanic Established Populations for Epidemiologic Studies of the Elderly. Am J Epidemiol., 169(9), 1092-1101.

Wight RG, Aneshensel CS, Miller-Martinez D, et al. 2006. Urban neighborhood context, educational attainment, and cognitive function among older adults. Am J Epidemiol., 163(12), 1071-1078.

In a small study, 266 older adults with mild cognitive impairment (aged 70+) received a daily dose of 0.8 mg folic acid, 0.5 mg vitamin B12 and 20 mg vitamin B6 or a placebo for two years. Those treated with B vitamins had significantly lower levels of homocysteine at the end of the trial (high homocysteine is a known risk factor for age-related cognitive decline and dementia). Moreover, this was associated with a significantly slower rate of brain shrinkage.

However, while there were significant effects on homocysteine level, brain atrophy, and executive function, it wasn’t until results were separated on the basis of baseline homocysteine levels that we get really dramatic results.

It was the group with high homocysteine levels at the start of the study who really benefited from the high doses of B vitamins. For them, brain atrophy was cut by half, and there were clear benefits in episodic memory, semantic memory, and global cognitive function, not just executive function. Among those with high baseline homocysteine who received the placebo, significant cognitive decline occurred.

The level of B vitamins in the supplements was considerably greater than the recommended standard. However, caution must be taken in dosing yourself with supplements, because folic acid can have negative effects. Better to try and get your diet right first.

A longer and larger follow-up study is now planned, and hopefully that will tell us if such treatment can keep MCI developing into Alzheimer’s.

A new study finds out why curcumin might help protect against dementia, and links two factors associated with Alzheimer’s and Parkinson’s diseases: DNA damage by reactive oxygen species (ROS), and excessive levels of copper and iron in parts of the brain. It turns out that high levels of copper or iron help generate large numbers of ROS and interfere with DNA repair.

While small amounts of iron and copper are vital, these are normally bound by proteins. However, when there’s too much, it can overwhelm the proteins and the result is "free" iron or copper ions circulating in the blood, able to initiate chemical reactions that produce reactive oxygen species. Moreover, the free copper and iron also interferes with the activity of two enzymes that repair DNA, NEIL1 and NEIL2.

However, the curry spice curcumin binds to iron and copper and was extremely effective in protecting the NEIL enzymes from the metals.

Hegde, M.L., Hegde, P.M. , Rao, K.S.J. & Mitra, S. 2011. Oxidative Genome Damage and Its Repair in Neurodegenerative Diseases: Function of Transition Metals as a Double-Edged Sword. Journal of Alzheimer's Disease , 25 (1), 183-198.

A study following 837 people with MCI, of whom 414 (49.5%) had at least one vascular risk factor, has found that those with risk factors such as high blood pressure, diabetes, cerebrovascular disease and high cholesterol were twice as likely to develop Alzheimer's disease. Over five years, 52% of those with risk factors developed Alzheimer's, compared to 36% of those with no risk factors In total, 298 people (35.6%) developed Alzheimer's.

However, of those with vascular risk factors, those receiving full treatment for their vascular problems were 39% less likely to develop Alzheimer's disease than those receiving no treatment, and those receiving some treatments were 26% less likely to develop the disease.

Treatment of risk factors included using high blood pressure medicines, insulin, cholesterol-lowering drugs and diet control. Smoking and drinking were considered treated if the person stopped smoking or drinking at the start of the study.

The new label of ‘metabolic syndrome’ applies to those having three or more of the following risk factors: high blood pressure, excess belly fat, higher than normal triglycerides, high blood sugar and low high-density lipoprotein (HDL) cholesterol (the "good" cholesterol). Metabolic syndrome has been linked to increased risk of heart attack.

A new French study, involving over 7,000 older adults (65+) has found that those with metabolic syndrome were 20% more likely to show cognitive decline on a memory test (MMSE) over a two or four year interval. They were also 13% more likely to show cognitive decline on a visual working memory test. Specifically, higher triglycerides and low HDL cholesterol were linked to poorer memory scores; diabetes (but not higher fasting blood sugar) was linked to poorer visual working memory and word fluency scores.

The findings point to the importance of managing the symptoms of metabolic syndrome.

High cholesterol and blood pressure in middle age tied to early memory problems

Another study, involving some 4800 middle-aged adults (average age 55), has found that those with higher cardiovascular risk were more likely to have lower cognitive function and a faster rate of cognitive decline over a 10-year period. A 10% higher cardiovascular risk was associated not only with increased rate of overall mental decline, but also poorer cognitive test scores in all areas except reasoning for men and fluency for women.

The cardiovascular risk score is based on age, sex, HDL cholesterol, total cholesterol, systolic blood pressure and whether participants smoked or had diabetes.

Memory problems may be sign of stroke risk

A very large study (part of the REGARDS study) tested people age 45 and older (average age 67) who had never had a stroke. Some 14,842 people took a verbal fluency test, and 17,851 people took a word recall memory test. In the next 4.5 years, 123 participants who had taken the verbal fluency test and 129 participants who had taken the memory test experienced a stroke.

Those who had scored in the bottom 20% for verbal fluency were 3.6 times more likely to develop a stroke than those who scored in the top 20%. For the memory test, those who scored in the bottom 20% were 3.5 times more likely to have a stroke than those in the top quintile.

The effect was greatest at the younger ages. At age 50, those who scored in the bottom quintile of the memory test were 9.4 times more likely to later have a stroke than those in the top quintile.

 

Together, these studies, which are consistent with many previous studies, confirm that cardiovascular problems and diabetes add to the risk of greater cognitive decline (and possible dementia) in old age. And point to the importance of treating these problems as soon as they appear.

[2147] Raffaitin C, Féart C, Le Goff M, Amieva H, Helmer C, Akbaraly TN, Tzourio C, Gin H, Barberger-Gateau P. Metabolic syndrome and cognitive decline in French elders. Neurology [Internet]. 2011 ;76(6):518 - 525. Available from: http://www.neurology.org/content/76/6/518.abstract

The findings of the second and third studies are to be presented at the American Academy of Neurology's 63rd Annual Meeting in Honolulu April 9 to April 16, 2011

A number of studies have provided evidence that eating breakfast has an immediate benefit for cognitive performance in children. Now a new study suggests some “good” breakfasts are better than others.

A Japanese study of 290 healthy, well-nourished children, has revealed that those whose breakfast staple was white rice had a significantly larger ratio of gray matter in their brains, and several significantly larger regions, including the left superior temporal gyrus and bilateral caudate. Those who habitually ate white bread had significantly larger regional gray and white matter volumes of several regions, including the orbitofrontal gyri, right precentral gyrus and postcentral gyrus. Overall IQ scores, and scores on the perceptual organization subcomponent in particular, were significantly higher for the rice group.

One possible reason for the difference may be the difference in the glycemic index (GI) of these two substances; foods with a low GI are associated with less blood-glucose fluctuation than are those with a high GI. There is also a difference in fat content, with those eating white bread typically consuming more fat than those eating a rice-based breakfast. High levels of fat have been shown to reduce the expression of BDNF.

Regardless of the reason for the difference, the fact that breakfast staple type affects brain size and cognitive function in healthy children points to the importance of good nutrition during the years of brain development.

A study involving 80 college students (34 men and 46 women) between the ages of 18 and 40, has found that those given a caffeinated energy drink reported feeling more stimulated and less tired than those given a decaffeinated soda or no drink. However, although reaction times were faster for those consuming caffeine than those given a placebo drink or no drink, reaction times slowed for increasing doses of caffeine, suggesting that smaller amounts of caffeine are more effective.

The three caffeine groups were given caffeine levels of either 1.8 ml/kg, 3.6 ml/kg or 5.4 ml/kg. The computerized "go/no-go" test which tested their reaction times was given half an hour after consuming the drinks.

In another study, 52 children aged 12-17 drank flattened Sprite containing caffeine at four concentrations: 0, 50 mg, 100 mg or 200 mg. Changes in blood pressure and heart rate were then checked every 10 minutes for one hour, at which point they were given a questionnaire and an opportunity to eat all they wanted of certain types of junk food.

Interestingly, there were significant gender differences, with boys drinking high-caffeine Sprite showing greater increases in diastolic blood pressure (the lower number) than boys drinking the low-caffeine Sprite, but girls being unaffected. Boys were also more inclined to report consuming caffeine for energy or “the rush”, than girls were.

Those participants who ingested the most caffeine also ate more high-sugar snack foods in the laboratory, and reported higher protein and fat consumption outside the lab.

A study involving 676 children (7-9) in rural Nepal has found that those whose mothers received iron, folic acid and vitamin A supplementation during their pregnancies and for three months after the birth performed better on some measures of intellectual and motor functioning compared to offspring of mothers who received vitamin A alone. However, there was no significant benefit for those whose mothers received iron, folic acid and zinc (plus vitamin A), or multiple micronutrients.

A negative effect of adding zinc is consistent with other research indicating that zinc inhibits iron absorption. Interestingly, new “ground-breaking” research demonstrates further the complexity of iron’s effects on the body. The researcher argues that many neurodegenerative diseases (such as Alzheimer’s) are partly caused by poorly bound iron, and it is vital to consume nutrients which bind iron and prevent the production of the toxins it will otherwise produce.

Such nutrients include brightly-colored fruits (especially purple) and vegetables, and green tea.

It’s also argued that Vitamin C is only beneficial if iron is safely bound, and if it’s not, excess Vitamin C might be harmful.

Following indications that the curry spice curcumin (the active ingredient in turmeric) may help protect brain cells from damage, two new studies have been testing a compound called CNB-001, derived from curcumin.

The first (rabbit) study found that CNB-001 is at least as effective as the only existing drug used to treat stroke (TPA), without the unwanted side-effect of reducing clotting in the blood vessels of the brain.

The second study found that CNB-001 dramatically reversed the behavioral deficits in both locomotion and memory in brain-injured rats. As with stroke, CNB-001 was again found to maintain the critical signaling pathways required for nerve cell survival, as well as the connections between nerve cells that are lost with the injury.

At present, there is no treatment for TBI, and only one FDA-approved drug for ischemic stroke

More evidence that vascular disease plays a crucial role in age-related cognitive impairment and Alzheimer’s comes from data from participants in the Alzheimer's Disease Neuroimaging Initiative.

The study involved more than 800 older adults (55-90), including around 200 cognitively normal individuals, around 400 people with mild cognitive impairment, and 200 people with Alzheimer's disease. The first two groups were followed for 3 years, and the Alzheimer’s patients for two. The study found that the extent of white matter hyperintensities (areas of damaged brain tissue typically caused by cardiovascular disease) was an important predictor of cognitive decline.

Participants whose white matter hyperintensities were significantly above average at the beginning of the study lost more points each year in cognitive testing than those whose white matter hyperintensities were average at baseline. Those with mild cognitive impairment or Alzheimer's disease at baseline had additional declines on their cognitive testing each year, meaning that the presence of white matter hyperintensities and MCI or Alzheimer's disease together added up to even faster and steeper cognitive decline.

The crucial point is that this was happening in the absence of major cardiovascular events such as heart attacks, indicating that it’s not enough to just reduce your cardiovascular risk factors to a moderate level — every little bit of vascular damage counts.

Previous research has indicated that obesity in middle-age is linked to higher risk of cognitive decline and dementia in old age. Now a study of 32 middle-aged adults (40-60) has revealed that although obese, overweight and normal-weight participants all performed equally well on a difficult cognitive task (a working memory task called the 2-Back task), obese individuals displayed significantly lower activation in the right inferior parietal cortex. They also had lower insulin sensitivity than their normal weight and overweight peers (poor insulin sensitivity may ultimately lead to diabetes). Analysis pointed to the impaired insulin sensitivity mediating the relationship between task-related activation in that region and BMI.

This suggests that it is insulin sensitivity that is responsible for the higher risk of cognitive impairment later in life. The good news is that insulin sensitivity is able to be modified through exercise and diet.

A follow-up study to determine if a 12-week exercise intervention can reverse the differences is planned.

A small study comparing 18 obese adolescents with type 2 diabetes and equally obese adolescents without diabetes or pre-diabetes has found that those with diabetes had significantly impaired cognitive performance, as well as clear abnormalities in the integrity of their white matter (specifically, reduced white matter volume, especially in the frontal lobe, as well as impaired integrity in both white and grey matter). Similar abnormalities have previously been found in adults with type 2 diabetes, but the subjects were elderly and, after many years of diabetes, generally had significant vascular disease. One study involving middle-aged diabetics found a reduction in the volume of the hippocampus, which was directly associated with poor glycaemic control.

It remains to be seen whether such changes can be reversed by exercise and diet interventions. While those with diabetes performed worse in all cognitive tasks tested, the differences were only significant for intellectual functioning, verbal memory and psychomotor efficiency.

I have often spoken of the mantra: What’s good for your heart is good for your brain. The links between cardiovascular risk factors and cognitive decline gets more confirmation in this latest finding that people whose hearts pumped less blood had smaller brains than those whose hearts pumped more blood. The study involved 1,504 participants of the decades-long Framingham Offspring Cohort who did not have a history of stroke, transient ischemic attack or dementia. Participants were 34 to 84 years old.

Worryingly, it wasn’t simply those with the least amount of blood pumping from the heart who had significantly more brain atrophy (equivalent to almost two years more brain aging) than the people with the highest cardiac index. Those with levels at the bottom end of normal showed similar levels of brain atrophy. Moreover, although only 7% of the participants had heart disease, 30% had a low cardiac index.

Following on from previous research with mice that demonstrated that a diet rich in methionine could increase the risk of developing Alzheimer's Disease through its effect on homocysteine levels, a new study has found that these effects were reversible if the mice then switched to a healthier diet. The mice, after five months on a methionine-rich diet, were divided into two groups, with one group continuing the diet and the second switching to the healthy diet for an additional two months. The cognitive impairment, and the build-up in amyloid plaques, was completely reversed after two months.

Methionine is an amino acid typically found in red meats, fish, beans, eggs, garlic, lentils, onions, yogurt and seeds. I note, however, that most of the items in this list are usually considered healthy! Fish, in particular, has been shown in a number of studies to reduce the risk of Alzheimer’s. The point is that methionine in itself is an essential amino acid and necessary for a healthy brain, but this indicates that, as with many foods, moderation is important. Clearly a balance is required; equally clearly, we still haven’t quite worked out the ‘perfect’ Alzheimer’s-prevention diet. Nevertheless, this study is welcome in demonstrating that diet can have such an effect on the brain, and adds to our knowledge of what makes a good diet for staving off dementia.

Following on from studies showing that a Mediterranean-like diet may be associated with a lower risk of Alzheimer's disease and may lengthen survival in people with Alzheimer's, a six-year study of 712 New Yorkers has revealed that those who were most closely following a Mediterranean-like diet were 36% less likely to have brain infarcts (small areas of dead tissue linked to thinking problems), compared to those who were least following the diet. Those moderately following the diet were 21% less likely to have brain damage. The association was comparable to the effects of high blood pressure — that is, not eating a Mediterranean-like diet was like having high blood pressure. The Mediterranean diet includes high intake of vegetables, legumes, fruits, cereals, fish and monounsaturated fatty acids such as olive oil; low intake of saturated fatty acids, dairy products, meat and poultry; and mild to moderate amounts of alcohol.

The study will be presented at the American Academy of Neurology's 62nd Annual Meeting in Toronto April 10 to April 17, 2010.

An analysis technique using artificial neural networks has revealed that the most important factors for predicting whether amnestic mild cognitive impairment (MCI-A) would develop into Alzheimer’s within 2 years were hyperglycemia, female gender and having the APOE4 gene (in that order). These were followed by the scores on attentional and short memory tests.

Tabaton, M. et al. 2010. Artificial Neural Networks Identify the Predictive Values of Risk Factors on the Conversion of Amnestic Mild Cognitive Impairment. Journal of Alzheimer's Disease, 19 (3), 1035-1040.

A study involving 733 participants from the Framingham Heart Study Offspring Cohort (average age 60) provides more evidence that excess abdominal fat places otherwise healthy, middle-aged people at greater risk for dementia later in life. The study also confirms that a higher BMI (body mass index) is associated with lower brain volumes in both older and middle-aged adults. However the association between visceral fat and total brain volume was independent of BMI. Visceral fat differs from subcutaneous fat in that it is buried deeper, beneath the muscles, around the organs. While it can only be seen by CT imaging, a pot belly or thick waist suggests its presence. For women (who become particularly vulnerable to this after menopause), a waistline above 88 cm is regarded as signaling a dangerous amount of visceral fat. Regular vigorous exercise, and consumption of polyunsaturated fats rather than saturated fats, is recommended.

A variant of a gene called the fat mass and obesity associated (FTO) gene causes people to gain weight and puts them at risk for obesity. The gene variant is found in nearly half of all people in the U.S. with European ancestry, around one-quarter of U.S. Hispanics, 15 percent of African Americans and 15 percent of Asian Americans. A new study involving 206 healthy elderly subjects from around the U.S. now suggests that this gene variant is also associated with loss of brain tissue. It’s not clear why, but the gene is highly expressed in the brain. Those with the "bad" version of the FTO gene had an average of 8% less tissue in the frontal lobes, and 12% less in the occipital lobes. The brain differences could not be directly attributed to other obesity-related factors (cholesterol levels, hypertension, or the volume of white matter hyperintensities), which didn’t vary between carriers and non-carriers. But if you have this gene variant, your weight is associated with neuron loss, and if you don't, it isn’t. The finding emphasizes the need for those with the gene to fight weight gain (and brain loss) by exercising and eating healthily.

The largest ever trial of fish oil supplements has found no evidence that they offer benefits for cognitive function in older people. The British study enrolled 867 participants aged 70-80 years, and lasted two years. After two years, those receiving fish oil capsules had significantly higher levels of omega-3 fatty acids in their blood than those receiving placebo capsules. However, cognitive function did not decline in either group over the period. The researchers caution that it may be that more time is needed for benefits to show.