Worldwide variation in the doubling time of Alzheimer's disease incidence rates

Kathryn Ziegler-Graham, Ron Brookmeyer, Elizabeth Johnson, H. Michael Arrighi

Research output: Contribution to journalArticlepeer-review

Abstract

Background: The doubling time is the number of chronological years for the age-specific incidence rate to double in magnitude. Doubling times describe the rate of increase of the risk of Alzheimer's disease (AD) with advancing age. Estimates of doubling times of AD assist in understanding disease etiology and forecasting future disease prevalence. The objective of this study was to investigate regional and gender differences in the doubling of AD age-specific incidence rates. Methods: We identified all studies in the peer review literature that reported age-specific incidence rates for AD. We modeled the logarithm of the incidence rate as a linear function of age. We used both fixed effects models and random effects models to account for interstudy variation. Results: AD incidence rates exponentially increase with increasing age. The overall estimate of the doubling time was 5.5 years. The doubling times from studies performed in North America and Europe were 6.0 and 5.8, respectively; whereas the doubling times in all other parts of the world were 5.0. There was no significant geographic differences in doubling times (P = .3). Although the doubling times were slightly longer for men (6.5 years) than for women (5.4 years), the difference was not significant (P = .3). Conclusions: Doubling times of AD incidence rates are not statistically significantly different among populations throughout the world. The risk of AD grows exponentially with age, doubling approximately every 5 to 6 years. Although the shapes of the incidence curves are similar, there is considerable variation in absolute incidence rates throughout the world. Currently, there are limited epidemiologic data at the oldest ages, and further study is needed to accurately define the incidence curve above age 90.

Original languageEnglish (US)
Pages (from-to)316-323
Number of pages8
JournalAlzheimer's and Dementia
Volume4
Issue number5
DOIs
StatePublished - Sep 1 2008

Keywords

  • Alzheimer's disease
  • Incidence rates
  • Meta-Analysis
  • Statistics

ASJC Scopus subject areas

  • Epidemiology
  • Health Policy
  • Developmental Neuroscience
  • Clinical Neurology
  • Geriatrics and Gerontology
  • Psychiatry and Mental health
  • Cellular and Molecular Neuroscience

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