INCIDENCE OF DEMENTIA IN PREDOMINANTLY MALE U.S. VETERAN CENTENARIANS

Abstract

Background: Centenarians are the fastest growing age group globally, yet little is known about US Veteran centenarians’ incidence of dementia and its impact on survival.

Methods and Results: retrospective longitudinal cohort study of elderly U.S. Veterans. Subjects are community – dwelling Veterans living in rural areas, born between 1904 and 1914 who survived to at least age 80. The study included 47936 octogenarians, 27176 nonagenarians, and 1378 centenarians. Kaplan–Meier method was used to estimate the cumulative incidence of dementia within age groups. Incidence rates were compared using log-rank test.

Cox proportional-hazards model used to estimate unadjusted hazard ratios. Veteran centenarians were 92.5% male, 85.9% white, 38.3% widowed, 90.5% served in World War II and 72.1% had no service related disability. Significant differences in dementia incidence rate were observed. By age 89 years, the estimated risk for dementia was 0.21% in the centenarian group, 3.1% in the nonagenarian group and 9.1% in the octogenarian group. Whereas by age 99 years, the risk of dementia increased to 8.3% for the centenarian group and 20.4% for the nonagenarian group. The difference in incidence rate remained between the statistically significant across age group (P =<.0001). The Hazard Ratio for dementia incidence among octogenarians and nonagenarians compared with centenarians is 8.9 CI 95% (7.2- 10.8) and 2.7 CI 95% (2.3- 3.3), respectively.

Conclusion: While dementia is generally under-recognized in the elderly, the study found that being a centenarian remained significantly associated with a reduced risk of dementia compared to both octogenarians and nonagenarians.