Serum cholesterol changes after midlife and late-life cognition

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Abstract
Background: Longitudinal studies have shown that high serum total cholesterol (TC) at midlife is a risk factor for dementia/Alzheimer disease. The significance of TC later in life is unclear. Objective: To investigate changes in serum TC from midlife to late life and their relationship with late-life cognition. Methods: Participants of the Cardiovascular Risk Factors, Aging and Dementia study were derived from random, population-based samples previously studied in a survey in 1972, 1977, 1982, or 1987. After an average follow-up of 21 years, 1,449 individuals aged 65 to 79 were reexamined in 1998. Results: Serum TC levels decreased in most individuals. High midlife TC represented a risk factor for more severe cognitive impairment later in life, and the values were significantly different between the control, mild cognitive impairment, and dementia groups. There were no significant differences in serum TC at reexamination. A moderate decrease in serum TC from midlife to late life (0.5 to 2 mmol/L) was significantly associated with the risk of a more impaired late-life cognitive status, even after adjusting for age, follow-up time, sex, years of formal education, midlife cholesterol, changes in body mass index, APOE ε4 genotype, history of myocardial infarction/stroke/diabetes, and lipid-lowering treatment. Conclusions: The relationship between serum total cholesterol (TC) and dementia seems to be bidirectional. High midlife serum TC is a risk factor for subsequent dementia/Alzheimer disease, but decreasing serum TC after midlife may reflect ongoing disease processes and may represent a risk marker for late-life cognitive impairment.