obesity

Steep cholesterol decline in older women linked to Alzheimer's risk

February, 2011

A long-running study has found cholesterol levels at in mid-life were not linked to later dementia in women, but marked decline in cholesterol level over the study period was.

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.

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Obesity and body shape linked to poorer brain function in older women

August, 2010

The association between obesity and reduced cognitive function appears to only occur, in older women at least, in those whose excess weight is carried on their hips, not their waist.

A very large study of older women has found that although there was a small downward trend in cognitive function (as measured by the MMSE) with increasing obesity, this trend was almost entirely driven by those with a waist-hip ratio below 0.78 — that is, for women who carry excess weight around their hips, known as pear shapes (as opposed to carrying it around the waist, called apple shapes). The study of 8,745 post-menopausal women (aged 65-79) found a drop of around 2 points on the 100-point MMSE for those with a BMI over 40 compared to those who were of normal weight, after controlling for such variables as education, diabetes, heart disease and hypertension, all of which were also significantly associated with BMI and MMSE score. Because 86% of the participants were white, and women belonging to other ethnic groups were not equally distributed between BMI categories, only data from white women were used. Some 70% of the participants were overweight (36%) or obese (34%).

Fat around the middle is thought to make more estrogen, which protects cognitive function. However, although depositing fat around the waist may be better for the brain, it is said to increase the risk of cancer, diabetes and heart disease.

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