Blood Pressure and Risk of Vascular Dementia: Evidence From a Primary Care Registry and a Cohort Study of Transient Ischemic Attack and Stroke

Abstract

Background and purpose: Vascular dementia is the second most common form of dementia but reliable evidence on age-specific associations between blood pressure (BP) and risk of vascular dementia is limited and some studies have reported negative associations at older ages.

Methods: In a cohort of 4.28 million individuals, free of known vascular disease and dementia and identified from linked electronic primary care health records in the United Kingdom (Clinical Practice Research Datalink), we related BP to time to physician-diagnosed vascular dementia. We further determined associations between BP and dementia in a prospective population-based cohort of incident transient ischemic attack and stroke (Oxford Vascular Study).

Results: For a median follow-up of 7.0 years, 11 114 initial presentations of vascular dementia were observed in the primary care cohort after exclusion of the first 4 years of follow-up. The association between usual systolic BP and risk of vascular dementia decreased with age (hazard ratio per 20 mm Hg higher systolic BP, 1.62; 95% confidence interval, 1.13-2.35 at 30-50 years; 1.26, 1.18-1.35 at 51-70 years; 0.97, 0.92-1.03 at 71-90 years; P trend=0.006). Usual systolic BP remained predictive of vascular dementia after accounting for effect mediation by stroke and transient ischemic attack. In the population-based cohort, prior systolic BP was predictive of 5-year risk of dementia with no evidence of negative association at older ages.

Conclusions: BP is positively associated with risk of vascular dementia, irrespective of preceding transient ischemic attack or stroke. Previous reports of inverse associations in old age could not be confirmed.

Keywords: blood pressure; dementia; epidemiology; hypertension; transient ischemic attack.

Figure 1

Floating absolute risk of new onset dementia in the primary care cohort by systolic and diastolic blood pressure, stratified by age category (30-50,51-70,71-90). Model adjusted for BMI, smoking status, sex and an interaction term between age category and categorical blood pressure (plotted).

Figure 2

Hazard ratio per 20 mm Hg higher usual systolic blood pressure and 10 mm Hg higher usual diastolic blood pressure in the primary care cohort. Model adjusted for BMI, smoking status, sex, age category, an interaction term between age category and continuous age and an interaction term between age category and blood pressure (plotted). No. VaD refers to the number of vascular dementia events.

Figure 3

Risk of vascular dementia by onset of dementia (early onset: age at diagnosis or end of follow-up <65 years, late onset: age at diagnosis or end of follow-up ≥ 65 years), BMI and sex for individuals 70 years or less at baseline in the primary care cohort. Models adjusted for age, BMI, sex and smoking status. Models in subgroups further adjusted for an interaction term between BP and age at event (plotted, Onset subgroup), BMI categories and an interaction term between BP and BMI categories (plotted, BMI subgroup), an interaction term between BP and sex (plotted, sex subgroup). No. VaD refers to the number of vascular dementia events.

Figure 4

Risk of vascular dementia for individuals aged 71 to 90 years, by period of follow-up for (A) systolic blood pressure and (B) diastolic blood pressure in the primary care cohort. Model adjusted for blood pressure (plotted), age, sex, BMI and smoking status.