CUMULATIVE EXPOSURE TO ELEVATED BLOOD PRESSURE THROUGHOUT ADULTHOOD AND LATE-LIFE DEMENTIA RISK

Abstract

Hypertension, particularly in midlife, is associated with increased dementia risk. Cumulative exposure to elevated blood pressure is likely relevant, but few studies have data to estimate cumulative exposure to elevated blood pressure throughout midlife, particularly in ethnically diverse populations. The objective of this study was to examine the association of cumulative exposure to elevated systolic blood pressure between ages 30 and 50 with late-life dementia risk among black and white Americans. This is a cohort study of n=6,168 black (35%) and white (65%) Kaiser Permanente Northern California health plan members who were ages 30–35 in 1964–1973 and remained members as of January 1, 1996. Blood pressure was measured at clinical exams between1964–1985. Late-life dementia diagnosis was collected from medical records January 1, 1996-October 15, 2015. Cumulative exposure to elevated systolic blood pressure at ages 30–50 years was estimated with “area under the curve” for each person's systolic blood pressure trajectory from linear mixed effects models with age as the timescale and restricted cubic splines to account for nonlinearities. We examined the association between cumulative years of hypertension (systolic blood pressure >= 140 mmHg) and pre-hypertension (systolic blood pressure 120–139mmHg) between ages 30–50 years with late-life dementia incidence with Cox proportional hazards models adjusting for age (as timescale), sex, race, and education. Blood pressure was measured an average of 3.3 times (range 1–13) between 1964–1985. Between ages 30–50, estimated cumulative exposure to prehypertension was high (mean=12.7 years); estimated cumulative exposure to hypertension was lower (mean=1.2 years). Mean age at the start of dementia follow up in 1996 was 59 years (range 53–67 years). Over a mean of 15.2 years of follow-up, there were n=522 dementia cases. For every 5 years of cumulative exposure to pre-hypertension, dementia risk increased by 8% (hazard ratio (HR)=1.08; 95% CI=1.02–1.14). For every 5 years of cumulative exposure to hypertension, dementia risk increased by 24% (HR=1.24; 95% CI=1.12–1.36). The association between cumulative exposure to elevated systolic blood pressure did not differ by race. Cumulative exposure to elevated systolic blood pressure throughout adulthood is associated with late-life dementia risk in an ethnically diverse population.