Cognitive Ageing in Africa: Systematic Review and Meta-Analysis of Pre-Dementia Prevalence and Associated Factors

Africa is experiencing rapid population ageing, yet the prevalence and determinants of pre-dementia stages - mild cognitive impairment (MCI) and subjective cognitive decline (SCD) - remain poorly defined. Global reviews include only a few African studies, limiting reliable estimates and obscuring regional risk factors. This study provides the first comprehensive synthesis of pre-dementia prevalence and associated factors across Africa.

We systematically searched PubMed, Embase, Web of Science, and African-specific databases from inception to March 2025. Studies reporting MCI or SCD prevalence in adults aged ≥50 years were included. Data were pooled using random-effects meta-analysis. Subgroup analyses examined heterogeneity by diagnostic criteria, setting, and study features. Meta-regression assessed links with demographic and cardiometabolic factors. Study quality was evaluated using the Joanna Briggs Institute prevalence checklist.

Twenty-eight studies from nine countries included 26,067 participants and 5,924 cases (SCD: 2,318 participants, 1,162 cases; MCI: 23,749 participants, 4,762 cases). Pooled prevalence was 50% (95% Confidence Interval [CI], 40 to 59%) for SCD and 20% (95% CI, 14 to 28%) for MCI. Heterogeneity for MCI was extreme (I²≈99%), mainly due to methodological variation. Studies using neuropsychological cut-offs alone reported nearly threefold higher MCI prevalence than those applying clinical criteria. Meta-regression identified associations between MCI prevalence and hypertension (β=.052; P=.017) and diabetes (β 0.053; P=.024).

Pre-dementia stages are common in African older adults. Methodological variation underscores the need for standardized, culturally validated criteria. Cardiometabolic comorbidities are key modifiable risks, supporting integrated interventions for cognitive health in Africa.