Lifetime risk of incident dementia and incident mild cognitive impairment in older adults.

introductionWe estimated the lifetime risk of incident dementia and mild cognitive impairment (MCI) from ages 55-105 and examined differences by sex and race.

methodsData were drawn from five harmonized longitudinal cohort studies at the Rush Alzheimer's Disease Center, including 4611 participants for dementia and 3915 for MCI. Diagnoses were based on annual clinical evaluations. Lifetime risk was estimated using nonparametric cumulative incidence curves by age conditional on being alive and event-free at the index age, accounting for competing mortality and delayed study entry, stratified by sex and race.

resultsLifetime risk from age 55 was 43% (95% confidence interval [CI]: 38%-47%) for dementia and 62% (95% CI: 57%-67%) for MCI. Female participants had higher risks than male participants, and racial differences were modest. DISCUSSION: These findings extend lifetime risk estimation beyond age 90 among diverse older adults and provide MCI estimates, emphasizing equity-focused prevention and public health strategies to reduce cognitive impairment. HIGHLIGHTS: Lifetime risk (cumulative incidence) of dementia and mild cognitive impairment (MCI) was estimated from ages 55 to 105 using nonparametric cumulative incidence models accounting for competing risk of death and left truncation. The estimated lifetime risk was 43% for incident dementia and 62% for MCI, with risk rising steeply after age 75 and appearing to level off at the oldest ages. Women and Black participants showed higher lifetime risks, partly reflecting mortality and selective survival dynamics. Exploratory analyses suggested elevated risks among Latino participants and those with a history of stroke. These findings extend lifetime risk estimation beyond age 90 and highlight the need for equitable, culturally informed dementia prevention and monitoring strategies.