LIFETIME RISK OF DEMENTIA AND ALZHEIMERS-DISEASE - THE IMPACT OF MORTALITY ON RISK ESTIMATES IN THE FRAMINGHAM-STUDY

We estimated the remaining lifetime risks of developing Alzheimer's di sease (AD) and dementia from all causes, based on data from longitudin al population studies. The risk of developing AD during one's lifetime depends on both disease incidence and life expectancy. Conventional e stimates of cumulative incidence overestimate the risk when there is a substantial probability of mortality due to competing causes. A total of 2,611 cognitively intact subjects (1,061 men, 1,550 women; mean ag e, 66 +/- 7 years) were prospectively evaluated for the development of AD or other dementia. A modified survival analysis was used to estima te both cumulative incidence and the sex-specific remaining lifetime r isk estimates for quinquennial age groups above age 65 years. Over a 2 0-year follow-up period, 198 subjects developed dementia (120 with AD) . The remaining lifetime risk of AD or other dementia depended on sex, being higher in women, but varied little with age between 65 and 80 y ears. In a 65-year-old man, the remaining lifetime risk of AD was 6.3% (95% CI, 3.9 to 8.7) and the remaining lifetime risk of developing an y dementing illness was 10.9% (95% CI, 8.0 to 13.8); corresponding ris ks for a 65-year-old woman were 12% (95% CI, 9.2 to 14.8) and 19% (95% CI, 17.2 to 22.5). The cumulative incidence between age 65 and 100 ye ars was much higher: for AD, 25.5% in men and 28.1% in women; for deme ntia, 32.8% in men and 45% in women. The actual remaining lifetime ris k of AD or dementia varies with age, sex, and life expectancy and is l ower than the hypothetical risk estimated by a cumulative incidence in the same population.