Age of onset of hypertension and risk of dementia in the oldest-old: The 90+ Study.

Introduction: We investigated the association between age of onset of hypertension and dementia risk in an oldest-old cohort.

Methods: Participants are from The 90+ Study, a population-based longitudinal study of people aged 90+ who are survivors from the Leisure World Cohort Study. We estimated hypertension onset age using self-reported information from The 90+ Study and Leisure World Cohort Study, collected about 20 years earlier. A total of 559 participants without dementia were followed every 6 months for up to 10 years.

Results: A total of 224 participants developed dementia during follow-up (mean = 2.8 years). Compared with those without hypertension, participants whose hypertension onset age was 80 to 89 years had a lower dementia risk (hazard ratio = 0.58, P = .04) and participants with an onset age of 90+ years had the lowest risk (hazard ratio = 0.37, P = .004).

Discussion: Developing hypertension at older ages may protect against dementia. Understanding the mechanisms for this lower risk is important for determining ways to prevent dementia in the very elderly.