Introduction:

The proportion of elderly people in our population, particularly in developed countries, is rapidly increasing, probably as a result of better medical care and better nutrition. With this increase has come an increase in age-related diseases such as Alzheimer's. Alzheimer's disease is already a significant public health problem, and will become even more of one in the future. It not only affects the patient, but his or her family and friends who must provide care, patience and understanding.

Reducing the risk of Alzheimer's, therefore, is an important endeavor for medical scientists and society. Many scientists believe that the process that leads to Alzheimer's begins in midlife. In this perspective, the Finish medical scientists who wrote this paper investigated the correlation between midlife high blood pressure and high cholesterol levels with the incidence of Alzheimer's in later life; they hoped to be able to show ways of reducing the risk of this devastating disease.

How the study was carried out:

The scientists gathered data from surveys of groups of people from two different regions of Finland carried out in 1972, 1977, 1982, and 1987. The data included blood pressure (both systolic and diastolic ¹) and serum cholesterol levels. 1,449 people who were still living in 1997 were randomly selected, with their consent, for a re-examination in 1998. The average time gap between the two examinations each person had was 21 years. Their average age at the second examination was 71.

The subjects were given a series of standard diagnostic clinical tests at the second examination to see if they had developed dementia and/or Alzheimer's disease. 57 of them (4%) were diagnosed as having dementia, and 48 of these had 'probable' or 'possible' Alzheimer's disease, with brain damage. None of these Alzheimer's patients had major vascular pathology shown by magnetic resonance imaging (MRI) scans. Four other patients were diagnosed as having Parkinson's disease and were excluded from the study.

In addition to blood pressure and cholesterol values, the scientists analyzed the subjects' education level, smoking habits, alcohol consumption, and whether they had circulatory problems.

The results:

The study showed that those subjects diagnosed as having Alzheimer's disease were generally older, had less formal education, weighed more, and, most importantly, had high systolic blood pressure and serum total cholesterol levels when they were examined in midlife.

Both high systolic blood pressure and high serum cholesterol in midlife were significant risk factors for Alzheimer's disease in later life. A systolic blood pressure over 160 mm Hg, or a total cholesterol of over 250 mg/dL (6.5 mmol/l) meant the subject was 2-3 times as likely to develop Alzheimer's disease in later life, varying slightly according to the method used.

High midlife diastolic blood pressure did not prove to be a risk factor in this analysis, although some other studies have indicated that it might be.

Subjects in midlife who had both a high systolic blood pressure and a high serum cholesterol level had an even greater risk of developing Alzheimer's disease - between 2.5 and 3.5 times that of those with normal values for both measurements. Even borderline high systolic blood pressure (140-159 mm Hg) proved to have a higher risk.

Those who had had circulatory problems during the interval between the two examinations, such as heart attacks or strokes, also had a greater risk of developing Alzheimer's disease. However, patients who consumed alcohol were found to be less likely to get Alzheimer's.

Often the subjects in the study had been treated for high blood pressure and high cholesterol levels. The way the study was carried out doesn't exclude the possibility that treatments for these conditions may have influenced the outcome. Nevertheless, the results were consistent with other studies of elderly Finnish men.

Comment:

An obvious question is whether the two main risk factors identified (high blood pressure and increased cholesterol levels) in fact produce degenerative changes in the blood vessels supplying the brain (atherosclerosis), which then cause so-called 'vascular dementia'. The authors point out, however, that analyzing the results after taking into account cardiovascular events (such as a heart attack or stroke) provided the same results. They also felt that genetic factors did not play a role, as cholesterol changes are known to be independent of the "Alzheimer" gene (apolipoprotein E) type.

The Finnish scientists are convinced that high blood pressure and high cholesterol levels in midlife are independent risk factors for Alzheimer's disease. Support for this comes from a clinical study of the effects of treating elderly people with 'isolated systolic hypertension', which resulted in a decrease in the occurrence dementia.
Ironically, the authors found that the midlife patients who did not participate and take the later re-examination had, on average, higher blood pressure and higher cholesterol levels than those who were in the study group. They also point out that patients with mental difficulties are less likely to participate in clinical studies. Both these facts reinforce their findings.

Conclusion:

This study shows the importance of identifying and treating high blood pressure and high serum cholesterol levels at an early age, or as soon as possible. In this way the risk of getting Alzheimer's disease may be lowered, which is particularly important as the population of developed countries becomes proportionally older. Exercise, diet, stress reduction and appropriate medication are useful tools for lowering blood pressure and cholesterol levels. Check with your physician!