Low blood pressure and incidence of dementia in a very old sample: dependent on initial cognition.

Abstract

To examine whether initially low blood pressure is related to the incidence of dementia. A population-based prospective study. The Kungsholmen district of Stockholm, Sweden Three hundred four nondemented subjects aged 75 to 96 years at baseline. After an average of 3 years, 81 dementia cases were identified (67 with Alzheimer's disease cases). Compared with individuals with baseline systolic pressure of 141 to 179 mm Hg, those with systolic pressure < or = 140 mm Hg had a significantly higher risk of dementia (relative risk (RR) = 1.9, 95% confidence interval (CI), 1.2-3.2) and Alzheimer's disease (RR = 2.2, 95% CI, 1.2-3.8). However, the RR in relation to systolic pressure < or = 140 mm Hg was 1.3 (0.8-2.2) for all dementia and 1.5 (0.8-2.6) for Alzheimer's disease, when the baseline Mini-Mental State Examination (MMSE) score was included in the model as a dichotomous variable (< 24 vs > or = 24). Baseline MMSE < 24 significantly predicted the occurrence of dementia (RR = 6.9; 95% CI, 4.3-11.1). Systolic pressure < or = 140 mm Hg was significantly related to MMSE score < 24 at baseline. These data suggest that low blood pressure may be an early correlate of a dementing process although a causative effect cannot be definitely ruled out.