Declining Incident Dementia Rates Across Four Population-Based Birth Cohorts

Kevin J. Sullivan, Hiroko Dodge, Tiffany F. Hughes, Chung Chou H. Chang, Xinmei Zhu, Anran Liu, Mary Ganguli

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Abstract

BACKGROUND: Incidence rates of dementia appear to be declining in high-income countries according to several large epidemiological studies. We aimed to describe declining incident dementia rates across successive birth cohorts in a U.S. population-based sample and to explore the influences of sex and education on these trends. METHODS: We pooled data from two community-sampled prospective cohort studies with similar study aims and contiguous sampling regions: the Monongahela Valley Independent Elders Survey (1987-2001) and the Monongahela-Youghiogheny Healthy Aging Team (2006-Ongoing). We identified four decade-long birth cohorts spanning birth years 1902-1941. In an analysis sample of 3,010 participants (61% women, mean baseline age = 75.7 years, mean follow-up = 7.1 years), we identified 257 cases of incident dementia indicated by a Clinical Dementia Rating of 1.0 or higher. We used Poisson regression to model incident dementia rates by birth cohort, age, sex, education, and interactions of Sex × Cohort and Sex × Education. We further examined whether cohort effects varied by education, testing a Cohort × Education interaction and stratifying the models by education. RESULTS: Compared to the earliest birth cohort (1902-1911), each subsequent cohort had a significantly lower incident dementia rate (1912-1921: incidence rate ratio [IRR] = 0.655, 95% confidence interval [95% CI] = 0.477-0.899; 1922-1931: IRR = 0.387, 95% CI = 0.265-0.564; 1932-1941: IRR = 0.233, 95% CI = 0.121-0.449). We observed no significant interactions of either sex or education with birth cohort. CONCLUSIONS: A decline in incident dementia rates was observed across successive birth cohorts independent of sex, education, and age.

Original languageEnglish (US)
Pages (from-to)1439-1445
Number of pages7
JournalThe journals of gerontology. Series A, Biological sciences and medical sciences
Volume74
Issue number9
DOIs
StatePublished - Aug 16 2019

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Keywords

  • Cognition
  • Cognitive aging
  • Community-based
  • Epidemiology

ASJC Scopus subject areas

  • Aging
  • Geriatrics and Gerontology

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