The new epidemic: frequency of dementia in the Rotterdam Study.

Dementia is one of the most frequent and devastating disorders in the elderly. Due to the increased longevity and the increasing number of elderly people in our society, it is emerging more and more as a major health problem. We quantified the frequency and lifetime risk of dementia, and of subtypes of dementia, in the Rotterdam Study, a population-based prospective cohort study among 7, 983 subjects over the age of 55 years. The overall prevalence was 6. 4% and the overall incidence 1 per 100 person-years. Both prevalence and incidence increased strongly with age. Typical incidence estimates for age 65, 75 and 95 are 1 per 1,000, 1 per 100 and 1 per 10 person-years. One in 6 men, and almost 1 in 3 women, will suffer at least some of their lifetime from dementia.