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Risk factors for heart disease may also be risk factors for dementia, supposedly including Alzheimer's
(September 2005)

The cause of Alzheimer's Disease is still unknown. There have been lots of suggestions for preventing Alzheimer's (diet, exercise, hormones), but none is adequately documented. Although Alzheimer's is the major cause of dementia in older persons, reduction of blood supply to the brain (vascular dementia) is another major cause. A group of California investigators has analyzed 8,845 participants of a health maintenance organization who were screened between 1964 and 1973 at ages 40 to 44 years. The screenings included four heart disease risk factors - smoking patterns, presence of diabetes, blood pressure, and blood cholesterol levels. Thirty years later, 721 of these participants had dementia.

High blood pressure at enrollment (systolic over 140 millimeters of mercury and/or diastolic pressure over 90 millimeters of mercury) and ever having smoked increased risk of dementia by about 20 percent. Having a high cholesterol (over 240 milligrams) or diabetes increased dementia risk by about 40 percent. The authors then looked at the presence of single or multiple risk factors. Those with a single risk factor (for example, a high cholesterol) had a 27 percent increased risk, but the risk of dementia increased to about double if three or all four of the risk factors were present at enrollment.

The authors concluded "the presence of multiple cardiovascular risk factors at midlife substantially increases risk of late life dementia in a dose-dependent fashion".

Commentary: This is an intriguing study and an important one, but its design has clear limitations.

- The category "dementia" included Alzheimer's, vascular dementia, and memory impairment. The authors assume most of the dementia cases had Alzheimer's, but they do not have the evidence to back that assumption. It could well be that these four known heart disease risk factors increase the risk of vascular dementia and are not related to Alzheimer's. It is an important issue. If Alzheimer's were related to these heart attack risk factors, it would offer an approach to prevention; but this study does not prove the relationship. For that to occur, the heart disease risk factors would have to be related to proven Alzheimer's.

- The smoking variable was "never versus ever smoked". That is much too simplistic.

Despite these concerns, the study results give additional reasons to control risk factors for heart disease - cholesterol elevation, high blood pressure, smoking - and to prevent diabetes by weight control and exercise. Controlling these risk factors will reduce the risk of coronary heart disease and heart attacks, and may reduce the risk of dementia.

Although there are other supportive studies indicating that heart disease risk factors are associated with increased risk for dementia, we still need additional studies to determine whether those heart disease risk factors are really related to Alzheimer's disease, and not just to vascular dementia.

Whitmer, R.A., et al. Midlife cardiovascular risk factors and risk of dementia in late life. Neurology. Vol 64 (January) Pgs 277-281. 2005.

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