Cholesterol Tied to Cognitive Function in Elderly

Source: Tufts University
May 16, 2002 (Reviewed: April 19, 2004)

Scientists suspect that some forms of age-related dementia may result from the same type of arterial damage that leads to cardiovascular disease. But they've had a more difficult time taking the argument one step further, because studies of the relationship between elevated serum cholesterol and cognitive function have produced mixed results. A study in a recent issue of Archives of Neurology, however, points to a connection between elevated serum lipids and development of dementia, and suggests a protective role for cholesterol-lowering statin drugs.

Analysis showed inverse relationship

University of California researchers recruited 1,037 postmenopausal women who were part of a recently completed 4-year study of hormone replacement therapy and heart disease. Lipid profiles and information about medication use - including the recent use of statin drugs - were culled from previously collected data. In addition, cognitive function was measured with a Modified Mini-Mental State Examination (a score of <84 points, or 1.5 standard deviations below the mean, indicated cognitive impairment).

The researchers were looking for a connection between changes in lipid profile over a 4-year period, recent statin use, and risk of dementia. They found a significant association between total cholesterol levels and cognitive function scores. The average test score of subjects in the lowest quartile of cholesterol levels was 93.5, whereas subjects in the highest quartile had an average score of 92.3 (p=0.01). The odds ratio for having cognitive impairment in those in the highest quartile compared with those in the lower three quartiles was 1.77 (95% CI 1.06--2.97). It's important to note that this difference was demonstrated after adjustment for potential confounding factors, including age, education, diabetes, history of cardiac surgery, and aspirin use.

Cognitive impairment was identified in 37 (6%) of the women taking statins and in 42 (9%) of those not taking statins. This difference suggested a protective effect of statins, but did not reach statistical significance (OR=67, 95% CI 0.42--1.05).

Proposed pathways

As suggested by this and earlier studies, elevated serum cholesterol may increase the risk of cognitive decline by contributing to subclinical vascular disease. Traditional vascular risk factors, including carotid atherosclerosis, atrial fibrillation, and increased coagulation factor I, may contribute to the vascular damage.

Although the use of statins did not have a clear impact in this study, this class of drugs could be protective through several proposed mechanisms. The most obvious is that they are a highly effective means of lowering blood lipids, although that may not be the whole answer. These drugs may also moderate the development of atherosclerosis by affecting smooth muscle function, macrophages, and platelets.

More research needed

Because this study included only elderly women, most of whom were white, the results cannot necessarily be generalized to men or to women of other races. It is also not clear from this study what role, if any, statins may play in reducing the risk of age-related cognitive decline.

But stay tuned, say the authors, as the potential link between blood lipids and brain function continues to develop.

Source

• Serum lipoprotein levels, statin use, and cognitive function in older women. K. Yaffe, E. Barrett-Connor, F. Lin,  et al., Arch Neurol, 2002, vol. 59, pp. 378--384

Related Links
Raised Homocysteine Levels: an Alzheimer Risk Factor
A Healthy Diet Is Linked to Better Cognitive Performance in Seniors
Alcohol and Dementias -- What To Advise?
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