Prevalence estimates of dementia in older adults in rural Kilimanjaro 2009-2010 and 2018-2019: is there evidence of changing prevalence?

Introduction: Although limited, existing epidemiological data on dementia in sub-Saharan Africa indicate that prevalence may be increasing; contrasting with recent decreases observed in high-income countries. We have previously reported the age-adjusted prevalence of dementia in rural Tanzania in 2009-2010 as 6.4% (95% confidence interval [CI] 4.9-7.9) in individuals aged ≥70 years. We aimed to repeat a community-based dementia prevalence study in the same setting to assess whether prevalence has changed.

Methods: This was a two-phase door-to-door community-based cross-sectional survey in Kilimanjaro, Tanzania. In Phase I, trained primary health workers screened all consenting individuals aged ≥60 years from 12 villages using previously validated, locally developed, tools (IDEA cognitive screen and IDEA-Instrumental Activities of Daily Living questionnaire). Screening was conducted using a mobile digital application (app) on a hand-held tablet. In Phase II, a stratified sample of those identified in Phase I were clinically assessed using the DSM-5 criteria and diagnoses subsequently confirmed by consensus panel.

Results: Of 3011 people who consented, 424 screened positive for probable dementia and 227 for possible dementia. During clinical assessment in Phase II, 105 individuals met DSM-5 dementia criteria. The age-adjusted prevalence of dementia was 4.6% (95% CI 2.9-6.4) in those aged ≥60 years and 8.9% (95% CI 6.1-11.8) in those aged ≥70 years. Prevalence rates increased significantly with age.

Conclusions: The prevalence of dementia in this rural Tanzanian population appears to have increased since 2010, although not significantly. Dementia is likely to become a significant health burden in this population as demographic transition continues.