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

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 < or = 140 mm Hg were more often diagnosed as demented than those 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 < or = 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.