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 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 < 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.

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.