Association of visit-to-visit variability in blood pressure with cognitive function in old age: prospective cohort study.

Abstract

To investigate the association between visit-to-visit variability in blood pressure and cognitive function in old age (>70 years). Prospective cohort study. PROSPER (PROspective Study of Pravastatin in the Elderly at Risk) study, a collaboration between centres in Ireland, Scotland, and the Netherlands. 5461 participants, mean age 75.3 years, who were at risk of cardiovascular disease. Blood pressure was measured every three months during an average of 3.2 years. Visit-to-visit variability in blood pressure was defined as the standard deviation of blood pressure measurements between visits. Four domains of cognitive function, testing selective attention, processing speed, and immediate and delayed memory. In a magnetic resonance imaging substudy of 553 participants, structural brain volumes, cerebral microbleeds, infarcts, and white matter hyperintensities were measured. Participants with higher visit-to-visit variability in systolic blood pressure had worse performance on all cognitive tests: attention (mean difference high versus low thirds) 3.08 seconds (95% confidence interval 0.85 to 5.31), processing speed -1.16 digits coded (95% confidence interval -1.69 to -0.63), immediate memory -0.27 pictures remembered (95% confidence interval -0.41 to -0.13), and delayed memory -0.30 pictures remembered (95% confidence interval -0.49 to -0.11). Furthermore, higher variability in both systolic and diastolic blood pressure was associated with lower hippocampal volume and cortical infarcts, and higher variability in diastolic blood pressure was associated with cerebral microbleeds (all P<0.05). All associations were adjusted for average blood pressure and cardiovascular risk factors. Higher visit-to-visit variability in blood pressure independent of average blood pressure was associated with impaired cognitive function in old age.