Blood pressure variability and risk of dementia in an elderly cohort, the Three-City Study

Abstract

Background: The relationship between blood pressure and dementia is incompletely understood in elderly individuals. Blood pressure variability may have a role in the risk of dementia.

Methods: This investigation was a cohort study of 6506 elderly individuals followed-up for 8 years (1999-2001 through 2008) with assessments at years 2, 4, and 7-8. Blood pressure was measured by electronic devices at baseline and at 2- and 4-year follow-up examinations. Cox proportional hazard models adjusted for potential confounders were used to estimate the risk of incident dementia according to blood pressure (means and coefficients of variation of the three measures).

Results: During the 40,151 person-years of follow-up 474 participants developed dementia. We observed no association between mean blood pressure and risk of dementia. In contrast, an increase of 1 standard deviation in the coefficient of variation of blood pressure was associated with a 10% increased risk of dementia. Analysis by deciles of the coefficient of variation showed that the higher the variability, the higher the risk of dementia (P<.02 for trend). In the fully adjusted Cox model, the risk of dementia for those in the highest decile of the coefficient of variation of systolic blood pressure was 1.77 (1.17-2.69) compared with the lowest decile.

Conclusions: In this cohort study, variability of blood pressure during follow-up was associated with an increased risk of incident dementia, whereas mean blood pressure was not. Limitation of blood pressure fluctuation may be an important target to preserve cognitive function in the elderly.

Keywords: Alzheimer's disease; Blood pressure; Cohort studies; Cox model; Hypertension; Risk factors in epidemiology; Vascular brain injury.