High-density lipoprotein cholesterol, cognitive function and mortality in a U.S. national cohort.

Low levels of both high density lipoprotein cholesterol (HDL) and cognitive function are associated with increased mortality risk. HDL plays an important role in brain metabolism. We test the hypotheses that the relative protective effect of high HDL level as related to mortality is greater in persons with impaired cognitive function than in others. Data were analyzed from a longitudinal mortality follow-up study of 4911 American men and women aged 60 years and over examined in 1988-1994 followed an average 8.5 yr. Measurements at baseline included HDL, a short index of cognitive function (SICF), socio-demographics, health status, and self-reported leisure-time physical activity. In proportional hazards regression analysis, no significant interaction of HDL with cognitive function was found (p = 0.08); there was a significant age-SICF interaction. After stratifying by age and adjusting for confounding by multiple variables, independent associations of HDL and SICF score with survival were strongest among the oldest persons. Consistent with its association with HDL, cognitive function and survival, controlling in addition for physical activity reduced the associations. In a nationwide cohort of older Americans, analyses demonstrated a lower risk of death independent of confounders among those high HDL and SICF scores, strongest among the oldest persons.