Developing hypertension at older ages may protect against dementia, according to a recent study. Understanding the mechanisms for this lower risk is important for determining ways to prevent dementia in the very elderly. Researchers investigated the association between age of onset of hypertension and dementia risk in an oldest-old cohort. Participants were from The 90+ Study, a population-based longitudinal study of people aged 90+ who are survivors from the Leisure World Cohort Study. They estimated hypertension onset age using self-reported information, collected about 20 years earlier. A total of 559 participants without dementia were followed every 6 months for up to 10 years. They found:

• 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 and participants with an onset age of 90+ years had the lowest risk.