Blood Pressure and Risk of Dementia: Results from the Rotterdam Study and the Gothenburg H-70 Study

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Abstract
The association between blood pressure and dementia is debated. Results from population-based studies on blood pressure and dementia are inconclusive, and most are performed in subjects younger than 80 years of age. We examined the relation between blood pressure and dementia and the possible effect modification of this relation by age in a pooled dataset based on two prospective population-based studies. Subjects came from the Rotterdam study (n = 6,668), a longitudinal population-based study among subjects aged 55 years and over, and from the Gothenburg H-70 Study (n = 317), a study on subjects aged 85 years at baseline. Screening and diagnostic procedures for assessment of dementia were similar at baseline and follow-up and comparable between studies. We estimated relative risks of dementia using Cox proportional hazards regression analysis, adjusted for age, gender and study location. The average follow-up was 2.1 years. During this period, 196 subjects developed dementia. The risk of dementia decreased with increasing blood pressure level (per 10 mm Hg systolic blood pressure: RR = 0.93, 95% CI = 0.88-0.99; per 10 mm Hg diastolic blood pressure: RR = 0.89, 95% CI = 0.79-1.00). This association was confined to subjects who used anthypertensive medication. Persons who were demented at baseline had a stronger blood pressure decline during follow-up than those who were non-demented. This study suggests an inverse association between blood pressure and dementia risk in elderly persons on antihypertensive medication. Possibly, they may need higher blood pressure levels to maintain an adequate cerebral perfusion. Alternatively, lower blood pressure may be secondary to brain lesions in preclinical stages of dementia.