Latest Research News
The APOE gene, the strongest genetic risk factor for Alzheimer’s disease, is known to be involved in cholesterol and lipid metabolism. Now the largest ever genetic study of Alzheimer’s disease, using DNA from more than 1.5 million people, has identified 90 points across the genome that were associated with an increased risk of both cardiovascular disease and Alzheimer’s disease.
The study focused on specific risk factors for heart disease (e.g., high BMI, type 2 diabetes, high cholesterol) to see if any were genetically related to Alzheimer’s risk. It was found that only those genes involved in lipid metabolism also related to Alzheimer's risk.
Six of the 90 regions had very strong effects on Alzheimer’s and heightened blood lipid levels, including several points within the CELF1/MTCH2/SPI1 region on chromosome 11 that was previously linked to the immune system.
The same genetic risk factors were also more common in people with a family history of Alzheimer’s, even though they had not themselves developed dementia or MCI.
The findings suggest that cardiovascular and Alzheimer's risk co-occur because of a shared genetic basis.
They also suggest a therapeutic target — namely, pathways involved in lipid metabolism.
Broce I, Karch C, Desikan R, et al. Dissecting the genetic relationship between cardiovascular risk factors and Alzheimer's disease. Acta Neuropathologica, published online Nov. 9, 2018.
As we all know, people are living longer and obesity is at appalling levels. For both these (completely separate!) reasons, we expect to see growing rates of dementia. A new analysis using data from the long-running Framingham Heart Study offers some hope to individuals, however.
Looking at the rate of dementia during four distinct periods in the late 1970s, late 1980s, 1990s, and 2000s, using data from 5205 older adults (60+), the researchers found that there was a progressive decline in the incidence of dementia at a given age, with an average reduction of 20% per decade since the 1970s (22%, 38%, and 44% during the second, third, and fourth epochs, respectively).
There are two important things to note about this finding:
- the decline occurred only in people with a high school education and above
- the decline was more pronounced with dementia caused by vascular diseases, such as stroke.
The cumulative risk over five years, adjusted for age and gender, were:
- 3.6 per 100 persons during the first period (late 1970s and early 1980s)
- 2.8 per 100 persons during the second period (late 1980s and early 1990s)
- 2.2 per 100 persons during the third period (late 1990s and early 2000s)
- 2.0 per 100 persons during the fourth period (late 2000s and early 2010s).
Part of the reason for the decline is put down to the decrease in vascular risk factors other than obesity and diabetes, and better management of cardiovascular diseases and stroke. But this doesn't completely explain the decrease. I would speculate that other reasons might include:
- increased mental stimulation
- improvements in lifestyle factors such as diet and exercise
- better health care for infectious and inflammatory conditions.
The finding is not completely unexpected. Recent epidemiological studies in the U.S., Canada, England, the Netherlands, Sweden and Denmark have all suggested that “a 75- to 85-year-old has a lower risk of having Alzheimer’s today than 15 or 20 years ago.” Which actually cuts to the heart of the issue: individual risk of dementia has gone down (for those taking care of their brain and body), but because more and more people are living longer, the numbers of people with dementia are increasing.
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.
Older adults who sleep poorly react to stress with increased inflammation
A study involving 83 older adults (average age 61) has found that poor sleepers reacted to a stressful situation with a significantly greater inflammatory response than good sleepers. High levels of inflammation increase the risk of several disorders, including cardiovascular disease and diabetes, and have been implicated in Alzheimer’s.
Each participant completed a self-report of sleep quality, perceived stress, loneliness and medication use. Around 27% were categorized as poor sleepers. Participants were given a series of tests of verbal and working memory designed to increase stress, with blood being taken before and after testing, as well as three more times over the next hour. The blood was tested for levels of a protein marker for inflammation (interleukin-6).
Poor sleepers reported more depressive symptoms, more loneliness and more perceived stress compared to good sleepers. Before cognitive testing, levels of IL-6 were the same for poor and good sleepers. However, while both groups showed increases in IL-6 after testing, poor sleepers showed a significantly larger increase — as much as four times larger and at a level found to increase risk for illness and death in older adults.
After accounting for loneliness, depression or perceived stress, this association remained. Surprisingly, there was no evidence that poor sleep led to worse cognitive performance, thus causing more stress. Poor sleepers did just as well on the tests as the good sleepers (although I note that we cannot rule out that poor sleepers were having to put in more effort to achieve the same results). Although there was a tendency for poor sleepers to be in a worse mood after testing (perhaps because they had to put in more effort? My own speculation), this mood change didn’t predict the increased inflammatory response.
The findings add to evidence that poor sleep (unfortunately common as people age) is an independent risk factor for cognitive and physical health, and suggest we should put more effort into dealing with it, rather than just accepting it as a corollary of age.
REM sleep disorder doubles risk of MCI, Parkinson's
A recent Mayo Clinic study has also found that people with rapid eye movement sleep behavior disorder (RBD) have twice the risk of developing mild cognitive impairment or Parkinson’s disease. Some 34% of those diagnosed with probable RBD developed MCI or Parkinson's disease within four years of entering the study, a rate 2.2 times greater than those with normal REM sleep.
Earlier research has found that 45% of those with RBD developed MCI or Parkinson's disease within five years of diagnosis, but these findings were based on clinical patients. The present study involved cognitively healthy older adults (70-89) participating in a population-based study of aging, who were diagnosed for probable RBD on the basis of the Mayo Sleep Questionnaire.
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.
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.
A ten-year study involving 7,239 older adults (65+) has found that each common health complaint increased dementia risk by an average of about 3%, and that these individual risks compounded. Thus, while a healthy older adult had about an 18% chance of developing dementia after 10 years, those with a dozen of these health complaints had, on average, closer to a 40% chance.
It’s important to note that these complaints were not for serious disorders that have been implicated in Alzheimer’s. The researchers constructed a ‘frailty’ index, involving 19 different health and wellbeing factors: overall health, eyesight, hearing, denture fit, arthritis/rheumatism, eye trouble, ear trouble, stomach trouble, kidney trouble, bladder control, bowel control, feet/ankle trouble, stuffy nose/sneezing, bone fractures, chest problems, cough, skin problems, dental problems, other problems.
Not all complaints are created equal. The most common complaint — arthritis/rheumatism —was only slightly higher among those with dementia. Two of the largest differences were poor eyesight (3% of the non-demented group vs 9% of those with dementia) and poor hearing (3% and 6%).
At the end of the study, 4,324 (60%) were still alive, and of these, 416 (9.6%) had Alzheimer's disease, 191 (4.4%) had another sort of dementia and 677 (15.7%) had other cognitive problems (but note that 1,023 were of uncertain cognitive ability).
While these results need to be confirmed in other research — the study used data from broader health surveys that weren’t specifically designed for this purpose, and many of those who died during the study will have probably had dementia — they do suggest the importance of maintaining good general health.
Common irregular heartbeat raises risk of dementia
In another study, which ran from 1994 to 2008 and followed 3,045 older adults (mean age 74 at study start), those with atrial fibrillation were found to have a significantly greater risk of developing Alzheimer’s.
At the beginning of the study, 4.3% of the participants had atrial fibrillation (the most common kind of chronically irregular heartbeat); a further 12.2% developed it during the study. Participants were followed for an average of seven years. Over this time, those with atrial fibrillation had a 40-50% higher risk of developing dementia of any type, including probable Alzheimer's disease. Overall, 18.8% of the participants developed some type of dementia during the course of the study.
While atrial fibrillation is associated with other cardiovascular risk factors and disease, this study shows that atrial fibrillation increases dementia risk more than just through this association. Possible mechanisms for this increased risk include:
- weakening the heart's pumping ability, leading to less oxygen going to the brain;
- increasing the chance of tiny blood clots going to the brain, causing small, clinically undetected strokes;
- a combination of these plus other factors that contribute to dementia such as inflammation.
The next step is to see whether any treatments for atrial fibrillation reduce the risk of developing dementia.
Stress may increase risk for Alzheimer's disease
And a rat study has shown that increased release of stress hormones leads to cognitive impairment and that characteristic of Alzheimer’s disease, tau tangles. The rats were subjected to stress for an hour every day for a month, by such means as overcrowding or being placed on a vibrating platform. These rats developed increased hyperphosphorylation of tau protein in the hippocampus and prefrontal cortex, and these changes were associated with memory deficits and impaired behavioral flexibility.
Previous research has shown that stress leads to that other characteristic of Alzheimer’s disease: the formation of beta-amyloid.
Following several recent studies pointing to the negative effect of air pollution on children’s cognitive performance (see this April 2010 news report and this May 2011 report), a study of public schools in Michigan has found that 62.5% of the 3660 schools in the state are located in areas with high levels of industrial pollution, and those in areas with the highest industrial air pollution levels had the lowest attendance rates and the highest proportions of students who failed to meet state educational testing standards in English and math. Attendance rates are a potential indicator of health levels.
Minority students were especially hit by this — 81.5% of African American and 62.1% of Hispanic students attend schools in the top 10% of the most polluted areas, compared to 44.4% of white students.
Almost all (95%) of the industrial air pollution around schools comes from 12 chemicals (diisocyanates, manganese, sulfuric acid, nickel, chlorine, chromium, trimethylbenzene, hydrochloric acid, molybdenum trioxide, lead, cobalt and glycol ethers) that are all implicated in negative health effects, including increased risk of respiratory, cardiovascular, developmental and neurological disorders, as well as cancer.
There are potentially two issues here: the first is that air pollution causes health issues which lower school attendance and thus impacts academic performance; the other is that the pollution also directly effects the brain, thus affecting cognitive performance.
A new mouse study looking at the effects of air pollution on learning and memory has now found that male mice exposed to polluted air for six hours a day, five days a week for 10 months (nearly half their lifespan), performed significantly more poorly on learning and memory tasks than those male mice living in filtered air. They also showed more signs of anxiety- and depressive-like behaviors.
These changes in behavior and cognition were linked to clear differences in the hippocampus — those exposed to polluted air had fewer dendritic spines in parts of the hippocampus (CA1 and CA3 regions), shorter dendrites and overall reduced cell complexity. Previous mouse research has also found that such pollution causes widespread inflammation in the body, and can be linked to high blood pressure, diabetes and obesity. In the present study, the same low-grade inflammation was found in the hippocampus. The hippocampus is particularly sensitive to damage caused by inflammation.
The level of pollution the mice were exposed to was equivalent to what people may be exposed to in some polluted urban areas.
A study involved 117 older adults (mean age 78) found those at greater risk of coronary artery disease had substantially greater risk for decline in verbal fluency and the ability to ignore irrelevant information. Verbal memory was not affected.
The findings add to a growing body of research linking cardiovascular risk factors and age-related cognitive decline, leading to the mantra: What’s good for the heart is good for the brain.
The study also found that the common classification into high and low risk groups was less useful in predicting cognitive decline than treating risk as a continuous factor. This is consistent with a growing view that no cognitive decline is ‘normal’, but is always underpinned by some preventable damage.
Risk for coronary artery disease was measured with the Framingham Coronary Risk Score, which uses age, cholesterol levels, blood pressure, presence of diabetes, and smoking status to generate a person's risk of stroke within 10 years. 37 (31%) had high scores. Age, education, gender, and stroke history were controlled for in the analysis.
Gooblar, J., Mack, W.J., Chui, H.C., DeCarli, C., Mungas, D., Reed, B.R. & Kramer, J.H. 2011. Framingham Coronary Risk Profile Predicts Poorer Executive Functioning in Older Nondemented Adults. Presented at the American Academy of Neurology annual meeting on Tuesday, April 12, 2011.
A study involving 200 older adults (70+) experiencing a stay in hospital has found that at discharge nearly a third (31.5%) had previously unrecognized low cognitive function (scoring below 25 on the MMSE if high-school-educated, or below 18 if not). This impairment had disappeared a month later for more than half (58%).The findings are consistent with previous research showing a lack of comprehension of discharge instructions, often resulting in rehospitalization.
The findings demonstrate the effects of hospitalization on seniors, and point to the need for healthcare professionals and family to offer additional support. It’s suggested that patient self-management may be better taught as an outpatient following discharge rather than at the time of hospital discharge.
Sleep disruption and stress are presumed to be significant factors in why this occurs.
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.
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
Research into the link, if any, between cholesterol and dementia, has been somewhat contradictory. A very long-running Swedish study may explain why. The study, involving 1,462 women aged 38-60 in 1968, has found that cholesterol measured in middle or old age showed no link to dementia, but there was a connection between dementia and the rate of decline in cholesterol level. Those women whose cholesterol levels decreased the most from middle to older age were more than twice as likely to develop dementia as those whose cholesterol levels increased or stayed the same (17.5% compared to 8.9%).After 32 years, 161 women had developed dementia.
Later in life, women with slightly higher body mass index, higher levels of cholesterol and higher blood pressure tend to be healthier overall than those whose weight, cholesterol and blood pressure are too low. But it is unclear whether "too low" cholesterol, BMI and blood pressure are risk factors for dementia or simply signs that dementia is developing, for reasons we do not yet understand.
On the other hand, a recent rat study has found that consuming a high cholesterol diet for five months caused memory impairment, cholinergic dysfunction, inflammation, enhanced cortical beta-amyloid and tau and induced microbleedings — all of which is strikingly similar to Alzheimer's pathology. And this finding is consistent with a number of other studies. So it does seem clear that the story of how exactly cholesterol impacts Alzheimer’s is a complex one that we are just beginning to unravel.
In light of other research indicating that the response of men and women to various substances (eg caffeine) may be different, we should also bear in mind that the results of the Swedish study may apply only to women.
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.
It’s been suggested before that Down syndrome and Alzheimer's are connected. Similarly, there has been evidence for connections between diabetes and Alzheimer’s, and cardiovascular disease and Alzheimer’s. Now new evidence shows that all of these share a common disease mechanism. According to animal and cell-culture studies, it seems all Alzheimer's disease patients harbor some cells with three copies of chromosome 21, known as trisomy 21, instead of the usual two. Trisomy 21 is characteristic of all the cells in people with Down syndrome. By age 30 to 40, all people with Down syndrome develop the same brain pathology seen in Alzheimer's. It now appears that amyloid protein is interfering with the microtubule transport system inside cells, essentially creating holes in the roads that move everything, including chromosomes, around inside the cells. Incorrect transportation of chromosomes when cells divide produces new cells with the wrong number of chromosomes and an abnormal assortment of genes. The beta amyloid gene is on chromosome 21; thus, having three copies produces extra beta amyloid. The damage to the microtubule network also interferes with the receptor needed to pull low-density lipoprotein (LDL — the ‘bad’ cholesterol) out of circulation, thus (probably) allowing bad cholesterol to build up (note that the ‘Alzheimer’s gene’ governs the low-density lipoprotein receptor). It is also likely that insulin receptors are unable to function properly, leading to diabetes.
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 implantable cardioverter defibrillator (ICD) is a small electronic device that monitors and regulates heartbeat, and many have been implanted in patients — an estimated 114,000 in the U.S. in 2006. Part of the implantation process involves ventricular defibrillation testing, which temporarily disrupts brain activity by causing a drop in blood pressure and blood flow to the brain. In a study involving 52 patients having cognitive tests several days before ICD surgery and again six weeks and six and 12 months afterwards, more than a third of participants had significant cognitive problems six weeks and six and 12 months after ICD surgery. Attention, short-term memory of visual words and objects, and auditory (spoken) words were most commonly affected. Although most patients regained their normal abilities by 12 months after surgery, a few (10%) first developed difficulties at that point. The results were unrelated to measurements of anxiety, depression and quality of life.
Older news items (pre-2010) brought over from the old website
More evidence bypass surgery not responsible for cognitive impairment
A 6-year study of 326 heart patients has found no differences in brain impairment between those who had on-pump coronary artery bypass surgery (152 patients), off-pump bypass surgery patients (75 patients), and those who had drugs and arterial stents to keep their blood vessels open instead of bypass surgery (99 patients). However, all of them were found to have experienced significant cognitive decline over the six-year study period on tests of verbal memory, visual memory, visuoconstruction, language, motor speed, psychomotor speed, attention, and executive function, when compared to 69 heart-healthy people who had no known risk factors for coronary artery disease. The findings provide more evidence that it is the disease and not the surgery that causes long-term cognitive problems.
Selnes, O.A. et al. 2009. Do Management Strategies for Coronary Artery Disease Influence 6-Year Cognitive Outcomes? Annals of Thoracic Surgery, 88, 445-454.
Heart failure linked to cognitive impairment
A study of 50 patients with chronic heart failure, matched with 50 people without HF, has found that patients with HF scored significantly lower than controls on 14 of 19 cognitive tests, and 46% of the HF patients were rated as having mild to severe cognitive impairment, compared to 16% of mild impairment in controls. The degree of cognitive impairment was closely related to the number of myocardial infarctions experienced. These findings have important implications for the care of patients with HF.
Sauvé, M.J. et al. 2009. Cognitive Impairments in Chronic Heart Failure: A Case Controlled Study. Journal of Cardiac Failure, 15 (1), 1-10.
Heart disease linked to worse cognition
Another report has come out from the large Whitehall study, this time on the subject of coronary heart disease and cognition. The study found that coronary heart disease was associated with a worse performance in mental processes such as reasoning, vocabulary and verbal fluency, and that the longer ago the heart disease had been diagnosed, the worse was the person's cognitive performance. This effect was particularly marked in men. Although there has been quite a lot of research on cardiovascular disease and impaired cognition, this is the first, large study to specifically examine the association between coronary heart disease and cognition. The major risk factors for coronary heart disease are all modifiable: cigarette smoking, diabetes, high cholesterol levels and high blood pressure. The findings also support the growing view that it is events happening in earlier life that have an impact on whether or not dementia develops in older age.
Singh-Manoux, A. et al. 2008. History of coronary heart disease and cognitive performance in midlife: the Whitehall II study. European Heart Journal, Advance Access published on July 22, 2008
Long-term cognitive decline in bypass patients not due to surgery
Another study has come out supporting the view that coronary bypass patients have no greater risk of long-term cognitive decline than patients not undergoing surgery. The study involved 152 patients who had bypass surgery and 92 patients with coronary artery disease who did not have surgical intervention. Patients had memory and other cognitive tests at the beginning of the study period, and after 3, 12, 36 and 72 months. The results showed that there were no significant differences in cognitive scores between the two groups at the beginning of the study. Both groups showed modest decline in cognitive performance during the study period, but there were no significant differences in the degree of decline between the groups after six years. It was suggested that the decline in both groups was related to the presence of risk factors for vascular disease.
Selnes, O.A. et al. 2008. Cognition 6 Years After Surgical or Medical Therapy for Coronary Artery Disease. Annals of Neurology, 63, 581-590.
Stroke risk factors may signal faster cognitive decline in elderly
Analysis of the stroke risks of over 17,000 people aged 45 and older (average 65.9) has found that a higher stroke risk score was associated with a significantly higher rate of cognitive decline. The study also identified three specific risk factors significantly associated with memory loss – high systolic blood pressure, diabetes, and left ventricular hypertrophy.
The findings were reported at the American Stroke Association’s International Stroke Conference 2008.
Review supports link between lifestyle factors and cognitive function in older adults
A review of 96 papers involving 36 very large, ongoing epidemiological studies in North America and Europe looking at factors involved in maintaining cognitive and emotional health in adults as they age has concluded that controlling cardiovascular risk factors, such as reducing blood pressure, reducing weight, reducing cholesterol, treating (or preferably avoiding) diabetes, and not smoking, is important for maintaining brain health as we age. The link between hypertension and cognitive decline was the most robust across studies. They also found a consistent close correlation between physical activity and brain health. However, they caution that more research is needed before specific recommendations can be made about which types of exercise and how much exercise are beneficial. They also found protective factors most consistently reported for cognitive health included higher education level, higher socio-economic status, emotional support, better initial performance on cognitive tests, better lung capacity, more physical exercise, moderate alcohol use, and use of vitamin supplements. Psychosocial factors, such as social disengagement and depressed mood, are associated with both poorer cognitive and emotional health in late life. Increased mental activity throughout life, such as learning new things, may also benefit brain health.
Hendrie, H.C. et al. 2006. The NIH Cognitive and Emotional Health Project: Report of the Critical Evaluation Study Committee. Alzheimer's & Dementia, 2(1), 12-32.
Why cardiac arrest may hinder ability to learn certain tasks
Cardiac arrest can take a particularly harsh toll on the hippocampus, the area of the brain that plays a critical role in memory and navigation. A new mouse study found that mice that had had a (surgically induced) heart attack had far more difficulty learning a new spatial task than did healthy mice (controls were given the surgery, but didn’t have a cardiac arrest induced). Mice in the heart attack group spent about eight minutes in cardiac arrest – enough time to stop the flow of oxygen to the brain. Analysis of the brain tissue found an overall 18% decrease in dendritic spine density in the hippocampus in the cardiac arrest mice compared to the control mice (dendritic spines are projections from neurons involved in sending signals throughout the central nervous system and the body). The researchers are now looking at how different types of social interactions influence the number and health of neurons that survive a heart attack.
Mervis, R.F., Bachstetter, A., Neigh, G.N., Glasper, E.R., Kofler, J., Traystman, R.J. & DeVries, A.C. 2004. Cardiac arrest with cardiopulmonary resuscitation reduces dendritic spine density in CA1 pyramidal cells and selectively alters acquisition of spatial memory. European Journal of Neuroscience, 20 (7), 1865 – 1872.
Inflammation associated with higher risk of age-related cognitive impairment
So-called “metabolic syndrome” is characterized most obviously by wide girth about the middle (being “apple-shaped”), as well as by high blood pressure and unhealthy levels of cholesterol, triglycerides and glucose in the blood. The syndrome is a well-known risk factor for cardiovascular disease. A new study finds the syndrome is also associated with a greater risk of cognitive impairment (hardly surprising, since many studies now indicate that cardiovascular risk factors are also risk factors for age-related cognitive impairment). The study tracked 2600 people, average age 74 years, over five years. Some 26% of those with the syndrome showed significant cognitive decline, compared to 21% of those without the syndrome. However, it appears the problem is not the syndrome so much as the high levels of inflammation that can result. About 30% of those with the syndrome plus high levels of inflammatory markers in their bloodstream showed significant cognitive decline. Those with the syndrome but no inflammation showed no increased risk.
Yaffe, K., Kanaya, A., Lindquist, K., Simonsick, E.M., Harris, T., Shorr, R.I., Tylavsky, F.A. & Newman, A.B. 2004. The Metabolic Syndrome, Inflammation, and Risk of Cognitive Decline. JAMA, 292, 2237-2242.
Age-related changes in the brain's white matter affect cognitive function
From around age 60, "white-matter lesions" appear in the brain, significantly affecting cognitive function. But without cognitive data from childhood, it is hard to know how much of the difference in cognitive abilities between elderly individuals is due to aging. A longitudinal study has been made possible by the Scottish Mental Survey of 1932, which gave 11-year-olds a validated cognitive test. Scottish researchers have tracked down healthy living men and women who took part in this Survey and retested 83 participants. Testing took place in 1999, when most participants were 78 years old.
It was found that the amount of white-matter lesions made a significant contribution to general cognitive ability differences in old age, independent of prior ability. The amount of white-matter lesions contributed 14.4% of the variance in cognitive scores; early IQ scores contributed 13.7%. The two factors were independent.
Although white-matter lesions are viewed as a normal part of aging, they are linked with other health problems, in particular to circulatory problems (including hypertension, diabetes, heart disease and cardiovascular risk factors).
Deary, I.J., Leaper, S.A., Murray, A.D., Staff, R.T. & Whalley, L.J. 2003. Cerebral White Matter Abnormalities and Lifetime Cognitive Change: A 67-Year Follow-Up of the Scottish Mental Survey of 1932. Psychology and Aging, 18 (1), 140-8.