We have prospectively followed over a 5-year period 434 volunteers who were at intake ambulatory, functional, presumably nondemented, and between 75 and 85 years of age. Fifty-six (an incidence of 3.53 per 100 person-years at risk) developed a progressive dementia: 32 met diagnostic criteria for Alzheimer's disease (AD) (an incidence of 2.0 per 100 person-years at risk), 15 had vascular or mixed dementia, and 9 had other disorders or remain undiagnosed. New cases of dementia were as common as myocardial infarction and twice as common as stroke. Risk factors for both dementia and AD were age (over 80) and gender (female); other reported risk factors such as family history, prior head injury, thyroid disease, maternal age, and smoking were not risk factors for AD in this elderly cohort. Prior stroke was the major risk factor for vascular or mixed dementia; diabetes and left ventricular hypertrophy but not a history of hypertension per se were also risk factors for vascular dementia. The major predictor of the development of AD was the mental status score on entry. The 58.5% of the cohort who made zero to two errors on a 33-item mental status test had a less than 0.6% per year chance of developing AD, whereas the 16% of the cohort with five to eight errors on this test developed AD at a rate of over 12% per year. Thus, it is possible to identify a large cohort of 80-year-olds who are at low risk for AD and a smaller cohort at very high risk.

The Bronx Aging Study is a 10-year prospective investigation of very elderly volunteers (mean age at study entry, 79 years; range, 75-85 years) designed to assess risk factors for dementia and coronary and cerebrovascular (stroke) diseases. Entry criteria included the absence of terminal illness and dementia. All subjects (n = 350) included in this report had at least two lipid and lipoprotein determinations. Overall, more than one third of subjects showed at least a 10% change in lipid and lipoprotein levels between the initial and final measurements. Moreover, mean levels for women were consistently different than those for men, and because of this finding subjects were classified into potential-risk categories based on the changes observed by using their sex-specific lipid and lipoprotein distributions. The incidences of cardiovascular disease, dementia, and death were compared between risk groups. Proportional-hazards analysis showed that in men a consistently low high density lipoprotein cholesterol level (less than or equal to 30 mg/dl) was independently associated with the development of myocardial infarction (p = 0.006), cardiovascular disease (p = 0.002), or death (p = 0.002). For women, however, a consistently elevated low density lipoprotein cholesterol level (greater than or equal to 171 mg/dl) was associated with myocardial infarction (p = 0.032). Thus, low high density lipoprotein cholesterol remains a powerful predictor of coronary heart disease risk for men even into old age, while elevated low density lipoprotein cholesterol continues to play a role in the development of myocardial infarction in women. The findings suggest that an unfavorable lipoprotein profile increases the risk of cardiovascular morbidity and mortality even at advanced ages for both men and women.

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