obesity

Obesity linked to inflammation & impaired brain function

A mouse study has found that obese mice had high levels of interleukin 1 in both their blood and their brains, and this was associated with:

  • high levels of inflammation,
  • low levels of a biochemical important to synapse function, and
  • impaired cognitive function.

Moreover, when fat was removed from the obese mice, interleukin levels dropped dramatically, and cognitive performance improved.

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Larger belly linked to memory problems in people with HIV

April, 2012

HIV-related cognitive impairment is significantly associated with a greater waist circumference, and in older adults, with diabetes.

A study involving 130 HIV-positive people has found that memory impairment was associated with a significantly larger waistline.

Some 40% of participants (average age 46) had impaired cognition. This group had an average waist circumference of 39 inches, compared to 35 inches for those without such problems. Memory impairment was also linked to diabetes in those older than 55 (15% of those with memory problems had diabetes compared to only 3% of those without memory problems).

Waistline was more important than BMI. Unfortunately, some anti-HIV drugs cause weight gain in this area.

The finding is consistent with evidence that abdominal weight is more important than overall weight for cognitive impairment and dementia in the general population.

For more about HIV-related cognitive impairment

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Obesity linked to better cognition in post-menopausal women

November, 2011
  • A new study suggests fat might help protect women from age-related cognitive decline.

Obesity has been linked to cognitive decline, but a new study involving 300 post-menopausal women has found that higher BMI was associated with higher cognitive scores.

Of the 300 women (average age 60), 158 were classified as obese (waist circumference of at least 88cm, or BMI of over 30). Cognitive performance was assessed in three tests: The Mini-Mental Statement Examination (MMSE), a clock-drawing test, and the Boston Abbreviated Test.

Both BMI and waist circumference were positively correlated with higher scores on both the MMSE and a composite cognitive score from all three tests. It’s suggested that the estrogen produced in a woman’s fat cells help protect cognitive function.

Interestingly, a previous report from the same researchers challenged the link found between metabolic syndrome and poorer cognitive function. This study, using data from a large Argentinean Cardiovascular Prevention Program, found no association between metabolic syndrome and cognitive decline — but the prevalence of metabolic syndrome and cognitive decline was higher in males than females. However, high inflammatory levels were associated with impairment of executive functions, and higher systolic blood pressure was associated with cognitive decline.

It seems clear that any connection between BMI and cognitive decline is a complex one. For example, two years ago I reported that, among older adults, higher BMI was associated with more brain atrophy (replicated below; for more recent articles relating obesity to cognitive impairment, click on the obesity link at the end of this report). Hypertension, inflammation, and diabetes have all been associated with greater risk of impairment and dementia. It seems likely that the connection between BMI and impairment is mediated through these and other factors. If your fat stores are not associated with such health risk factors, then the fat in itself is not likely to be harmful to your brain function — and may (if you’re a women) even help.

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Overweight and obese elderly have smaller brains

Analysis of brain scans from 94 people in their 70s who were still "cognitively normal" five years after the scan has revealed that people with higher body mass indexes had smaller brains on average, with the frontal and temporal lobes particularly affected (specifically, in the frontal lobes, anterior cingulate gyrus, hippocampus, and thalamus, in obese people, and in the basal ganglia and corona radiate of the overweight). The brains of the 51 overweight people were, on average, 6% smaller than those of the normal-weight participants, and those of the 14 obese people were 8% smaller. To put it in more comprehensible, and dramatic terms: "The brains of overweight people looked eight years older than the brains of those who were lean, and 16 years older in obese people." However, overall brain volume did not differ between overweight and obese persons. As yet unpublished research by the same researchers indicates that exercise protects these same brain regions: "The most strenuous kind of exercise can save about the same amount of brain tissue that is lost in the obese."

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Zilberman, J.M., Del Sueldo, M., Cerezo, G., Castellino, S., Theiler, E. & Vicario, A. 2011. Association Between Menopause, Obesity, and Cognitive Impairment. Presented at the Physiology of Cardiovascular Disease: Gender Disparities conference, October 12, at the University of Mississippi in Jackson.

Vicario, A., Del Sueldo, M., Zilberman, J. & Cerezo, G.H. 2011. The association between metabolic syndrome, inflammation and cognitive decline. Presented at the European Society of Hypertension (ESH) 2011: 21st European Meeting on Hypertension, June 17 - 20, Milan, Italy.

[733] Thompson, P. M., Raji C. A., Ho A. J., Parikshak N. N., Becker J. T., Lopez O. L., et al.
(2010).  Brain structure and obesity.
Human Brain Mapping. 31(3), 353 - 364.

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Cognitive impairment in obese improved by surgery

June, 2011

Consistent with evidence linking obesity and impaired cognition, a new study has found improved cognition in obese patients after bariatric surgery.

Growing evidence links obesity and poorer cognitive performance. Many factors associated with obesity, such as high blood pressure, type 2 diabetes and sleep apnea, damage the brain.

A study involving109 bariatric surgery patients and 41 obese control subjects has found that the bariatric surgery patients demonstrated improved memory and concentration 12 weeks after surgery, improving from the slightly impaired range to the normal range. That of the obese controls actually declined over this period. The improvement of those who had surgery seemed to be particularly related to improved blood pressure.

Study participants will be tested one year and two years after surgery.

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[2224] Gunstad, J., Strain G., Devlin M. J., Wing R., Cohen R. A., Paul R. H., et al.
(2010).  Improved memory function 12 weeks after bariatric surgery.
Surgery for Obesity and Related Diseases.

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Metabolic syndrome linked to memory loss in older people

March, 2011

Three more studies point to the increased risk of memory loss in older adults with cardiovascular problems.

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.

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[2147] Raffaitin, C., Féart C., Le Goff M., Amieva H., Helmer C., Akbaraly T. N., et al.
(2011).  Metabolic syndrome and cognitive decline in French elders.
Neurology. 76(6), 518 - 525.

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

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