Fourteen-year longitudinal study of vascular risk factors, APOE genotype, and cognition: the ARIC MRI Study.

BACKGROUND: Strokes, vascular risk factors, and apolipoprotein E (APOE) genotype are associated with cognitive decline in the elderly, but definitive evidence that these affect cognition as early as middle age is limited.
OBJECTIVE: We describe the relationships of APOE genotype, stroke, and vascular risk factors with cognitive change over a 14-year follow-up in the Atherosclerosis Risk in Communities (ARIC) Study cohort recruited while in middle age.
METHODS: Participants included a subset of the ARIC Study who underwent assessments of cognitive function and vascular risk factors. Four cognitive assessments were performed between 1990-1992 and 2004-2006. Cognitive assessments included the Delayed Word Recall (DWR) Test, the Digit Symbol Substitution (DSS) Test, and the Word Fluency (WF) Test. Vascular risk factors were assessed during the baseline visit in 1990-1992. Incident stroke was recorded over the 14 years of follow-up.
RESULTS: There were 1130 participants (mean age, 59 +/- 4.3 [SD] years; 62% women; 52% African-American) with longitudinal data. In multivariate, random-effects linear models adjusted for age, education, gender, and race, the risk factors diabetes and APOE epsilon4 genotype were independently associated with a decline in performance on the DSS test (both P < .005), whereas hypertension and stroke were not. For DWR, stroke and APOE epsilon4 genotype were independent predictors of decline (both P < .001). For the WF test, metabolic syndrome, hypertension, and stroke were independently associated with decline (all P < .005). No evidence of differential effects of risk factors on cognitive decline by race, gender, or interactions between risk factors was found.
CONCLUSIONS: The vascular risk factors diabetes and hypertension, a history of stroke itself, and APOE epsilon4 genotype independently contribute to cognitive decline in late middle age and early elderly years.