Are big blood pressure changes linked to dementia years later?

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Blood pressure variation may be related to dementia risk through autonomic disturbance or hemodynamic mechanisms, but its long-term associations were unclear. Researchers investigated whether the magnitude and direction of blood pressure changes over a period of years were associated with dementia risk.

In a prospective cohort study ongoing since 1989 in the Netherlands, they included 5,273 people who were free of dementia: 58.1% were women, and their mean age was 67.6 years (standard deviation 8.0). By 2016, 1,059 dementia cases had occurred during a median follow-up of 14.6 years.

Absolute variation in systolic blood pressure (SBP) was calculated as the absolute difference in SBP divided by the mean across two sequential visits, a median of 4.2 years apart; the first quantile was the reference. For the direction of change, researchers considered rises and falls in SBP and used the third quantile as the reference. They estimated dementia risk in relation to SBP variation measured at least 0, 5, 10 and 15 years before diagnosis, adjusting for age, sex, education, apolipoprotein E (APOE) genotype, vascular risk factors and cardiovascular disease history. They repeated the analysis for variation in diastolic blood pressure (DBP).

Large SBP variation was associated with increased dementia risk, with a more pronounced association when more time separated the variation assessment from diagnosis. For the highest quintile of variation, the hazard ratio (HR) was 1.08 (95% confidence interval [CI] 0.88–1.34; P = 0.337) for risk within 5 years of measurement and 3.13 (95% CI 2.05–4.77; P < 0.001) for risk at least 15 years after measurement. Higher long-term risk was associated with both large rises in SBP (highest quintile: HR 3.31, 95% CI 2.11–5.18; P < 0.001) and large falls (lowest quintile: HR 2.20, 95% CI 1.33–3.63; P = 0.002), whereas higher short-term risk was associated only with large falls (HR 1.21, 95% CI 1.00–1.48; P = 0.017). Similar findings were observed for DBP variation.

Although major confounders were assessed, residual confounding remains possible. Findings about variation over years may not generalize to variation over days or other shorter periods. The researchers concluded that large blood pressure variation over years was associated with increased long-term dementia risk, particularly when the variation occurred long before diagnosis; both large rises and falls were associated with elevated long-term risk.