Vascular causes of dementia may be more common than supposed. Vascular factors may also have a role in late-onset Alzheimer's disease, but the role of hypertension in the development of dementia is unclear.As part of the Longitudinal Population Study of 70-year-olds in Göteborg, Sweden, we analysed the relation between blood pressure and the development of dementia in the age intervals 70-75, 75-79, and 79-85 years in those non-demented at age 70 (n = 382). The sample was followed up for 15 years and examined repeatedly with a comprehensive investigation, including a psychiatric and physical examination. aParticipants who developed dementia at age 79-85 had higher systolic blood pressure at age 70 (mean 178 vs 164 mm Hg, p = 0.034) and higher diastolic blood pressure at ages 70 (101 vs 92, p = 0.004) and 75 (97 vs 90, p = 0.022) than those who did not develop dementia. For subtypes of dementia, higher diastolic blood pressure was recorded at age 70 (101, p = 0.019) for those developing Alzheimer's disease and at age 75 (101, p = 0.015) for those developing vascular dementia than for those who did not develop dementia. Participants with white-matter lesions on computed tomography at age 85 had higher blood pressure at age 70 than those without such lesions. Blood pressure declined in the years before dementia onset and was then similar to or lower than that in non-demented individuals.Previously increased blood pressure may increase the risk for dementia by inducing small-vessel disease and white-matter lesions. To what extent the decline in blood pressure before dementia onset is a consequence or a cause of the brain disease remains to be elucidated.

15-year longitudinal study of blood pressure and dementia