OBJECTIVE: To examine whether initially low blood pressure is related to the 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 at baseline.

MEASUREMENTS AND MAIN RESULTS: 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 ≤ 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 ≤ 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 ≥ 24). Baseline MMSE <24 significantly predicted the occurrence of dementia (RR = 6.9; 95% CI, 4.3–11.1). Systolic pressure ≤ 140 mm Hg was significantly related to MMSE score < 24 at baseline.

CONCLUSIONS: 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. J Am Geriatr Soc 47:723–726, 1999.