Low blood pressure and dementia in elderly people: the Kungsholmen project

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Abstract
Objective: To examine the relation between blood pressure and dementia in elderly people. Design: Cross sectional, population based study. Setting: Kungsholmen district of Stockholm, Sweden. Subjects: 1642 subjects aged 75-101 years. Main outcome measures: Prevalence and adjusted odds ratio of dementia by blood pressure. Results: People with systolic pressure 140 mm Hg: odds ratios (95% confidence interval) adjusted for age, sex, and education were 2.98 (2.17 to 4.08) for all dementias, 2.91 (1.93 to 4.38) for Alzheimer's disease, 2.00 (1.09 to 3.65) for vascular dementia, and 5.07 (2.65 to 9.70) for other dementias. Similar results were seen in subjects with diastolic pressure </=75 mm Hg compared with those with higher diastolic pressure. When severity and duration of dementia were taken into account, only moderate and severe dementia were found to be significantly related to relatively low blood pressure, and the association was stronger in subjects with longer disease duration. Use of hypotensive drugs and comorbidity with cardiovascular disease did not modify the results for all dementias, Alzheimer's disease, and other dementias but slightly reduced the association between vascular dementia and diastolic blood pressure. Conclusions: Both systolic and diastolic blood pressure were inversely related to prevalence of dementia in elderly people. We think that relatively low blood pressure is probably a complication of the dementia process, particularly Alzheimer's disease, although it is possible that low blood pressure may predispose a subpopulation to developing dementia. Key messages We studied prevalence of dementia in 1642 subjects aged 75-101 and found that those with relatively low blood pressure (</=140 mm Hg systolic, </=75 mm Hg diastolic) were significantly more likely to have dementia When severity and duration of dementia were taken into account, only moderate and severe dementia were found to be significantly related to low blood pressure, and the association was stronger in subjects with longer duration of disease Use of hypotensive drugs and comorbidity with cardiovascular disease could not account for the association We think that relatively low blood pressure is probably a complication of the dementia process, particularly Alzheimer's disease, but it is possible that low pressure may predispose some people to developing dementia