Low diastolic pressure and risk of dementia in very old people: a longitudinal study

Midlife high blood pressure is linked to late-life dementia. We sought to investigate the temporal relation of blood pressure to the risk of dementia and Alzhei-mer's disease (AD) among older adults.

A dementia-free cohort (n = 422) aged > or =81 years was followed for 3 years to detect dementia and AD cases (Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised criteria). The blood pressure was measured 4 times over a 9-year period starting from > or =75 years of age. The data were analyzed with Cox models controlling for potential confounders.

During the 954 person-years of follow- up, 89 subjects developed dementia (72 AD cases). Low diastolic pressure (<70 vs. 70-89 mm Hg) was associated with a multiadjusted hazard ratio of 2.13 [95% confidence interval (CI) = 1.05-4.32] for dementia and 2.16 (95% CI = 0.98-4.73) for AD occurring over a 6-to 9-year period, whereas high diastolic pressure (> or =90 mm Hg) was marginally related to a decreased hazard ratio of 0.58 (95% CI = 0.33-1.02) for dementia and 0.57 (95% CI = 0.30-1.09) for AD. Systolic pressure was not significantly related to dementia risk. Subjects who developed dementia had a greater decline in blood pressure than persons who did not, mainly during the 3-year period before dementia diagnosis.

Low diastolic pressure predicts the risk of dementia among very old people, and the blood pressure exhibits a substantial decline over around 3 years before the dementia syndrome becomes clinically evident.