Incidence of and risk factors for dementia in the Ibadan study of aging

J Am Geriatr Soc. 2011 May;59(5):869-74. doi: 10.1111/j.1532-5415.2011.03374.x.


Objectives: To describe the incidence of dementia in a representative sample of elderly Yoruba Nigerians and provide information about the risk factors.

Design: In-home face-to-face assessments conducted on a community cohort selected using multistage clustered sampling of households, with baseline between November 2003 and August 2004 (n=2,149) and follow-up approximately 39 months later (n=1,408).

Setting: Eight contiguous, predominantly Yoruba-speaking states in Nigeria.

Participants: Persons aged 65 and older free of dementia at baseline (n=1,225).

Measurements: Dementia was ascertained using two instruments: the 10-Word Delayed Recall Test and the Clinician Home-based Interview to assess Function, both with demonstrated validity and cultural applicability.

Results: At 3-year follow-up, 85 participants had developed dementia. With a total 3,888 risk years for the sample, the estimated incidence of dementia was 21.85 per 1,000 person-years (95% confidence interval=17.67-27.03). Compared with men, the age-adjusted hazard ratio (HR) for women was 2.12 (P=.002). Incidence increased linearly with age such that, compared with participant aged 65 to 74, the HR, adjusted for sex, for participants aged 75 to 84 was 2.84 (P<.001) and for those aged 85 and older was 4.13 (P<.001). Greater incidence of dementia was found with more-rural residence and poorer economic status. Participants with poor social engagement at baseline were at significantly greater risk of incident dementia.

Conclusion: Incident dementia in Yoruba Nigerians is higher than previously reported. Indices of social isolation are risk factors for incident dementia in this population.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Dementia / diagnosis
  • Dementia / epidemiology*
  • Female
  • Humans
  • Incidence
  • Male
  • Neuropsychological Tests
  • Nigeria / epidemiology
  • Proportional Hazards Models
  • Risk Factors
  • Social Isolation
  • Surveys and Questionnaires