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

OBJECTIVE: To examine whether initially low blood pressure is related to th e incidence of dementia. DESIGN: A population-based prospective study. SETTING: The Kungsholmen district of Stockholm, Sweden PARTICIPANTS: Three hundred four nondemented subjects aged 75 to 96 years a t baseline. MEASUREMENTS AND MAIN RESULTS: After an average of 3 years, 81 dementia cas es were identified (67 with Alzheimer's disease cases). Compared with indiv iduals with baseline systolic pressure of 141 to 179 mm Hg, those with syst olic pressure less than or equal to 140 mm Hg had a significantly higher ri sk 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 less than or equal to 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 th e baseline Mini-Mental State Examination (MMSE) score was included in the m odel as a dichotomous variable (< 24 vs greater than or equal to 24). Basel ine MMSE <24 significantly predicted the occurrence of dementia (RR = 6.9; 95% CI, 4.3-11.1). Systolic pressure I 140 mm Hg was significantly related to MMSE score <24 at baseline. CONCLUSIONS: These data suggest that low blood pressure may be an early cor relate of a dementing process although a causative effect cannot be definit ely ruled out.