To perform a systematic review of the literature on the prevalence of cognitive impairment and dementia in sub-Saharan Africa.

Five electronic databases were searched for relevant abstracts and to identify papers eligible for full-text review. A study was included if two authors agreed that it had a cohort, case–control or cross-sectional design and reported population-level data; was limited to black African adults older than 50 years or described as “elderly” or “old”; reported data for individuals residing in sub-Saharan Africa; and reported at least one measure of cognitive impairment or clinical outcomes relevant to cognitive decline. References of papers included in our study were searched to identify additional candidate publications. Disagreements about inclusion were adjudicated during discussions involving all authors. Data were extracted independently by two authors, using a form developed by the authors and tested on a sample of papers.

A total of 2320 unique papers was found; the full text of 87 was reviewed. Nineteen papers featuring 11 cross-sectional studies were included; all were published during 1995–2011. Studies occurred in Benin, Botswana, the Central African Republic, the Congo and Nigeria and enrolled approximately 10 500 participants. The prevalence of dementia ranged from 0%, in Nigeria, to 10.1% (95% confidence interval, CI: 8.6–11.8), also in Nigeria. The prevalence of cognitive impairment ranged from 6.3%, in Nigeria, to 25% (95% CI: 21.2–29.0), in the Central African Republic.

Prevalences of dementia and cognitive impairment in sub-Saharan Africa varied widely, with few published studies revealed by the literature search.