Abstract

Background: Dementia prevalence is rising globally, with low-and-middle-income countries disproportionately affected. However, dementia risk factors remain poorly characterized in sub-Saharan Africa, limiting prevention strategies. This study aimed to characterize the multidimensional risk factors for dementia among middle-aged and older Nigerians to inform context-appropriate interventions for Africa's aging population.

Methods: This cross-sectional baseline study recruited 1,152 adults aged 50 years and above across Lagos State using multistage cluster sampling. The primary outcome was screening-defined cognitive classification based on the IDEA tool (no dementia vs possible/probable dementia), while the ANU-ADRI was used to assess dementia-related risk exposures. The data was analyzed using descriptive statistics, chi-square tests, and logistic regression to identify predictors of dementia risk. A decision tree analysis was employed to determine significant splitting variables for risk classification.

 Results: The majority (85.2%) of participants were classified as having no dementia, while 8.7% and 6.1% showed possible and probable dementia, respectively. Decision tree analysis identified age and sex as primary predictors, with the highest prevalence of probable dementia observed in males aged 80–89 (20.8%) and females aged 75–84 (15.9%). Logistic regression revealed that depressive symptoms significantly increased the odds of dementia risk (OR: 2.82, 95% CI: 1.78–4.49, p < 0.0001), as did lower educational attainment of  <8 years (OR: 2.01, 95% CI: 1.42–3.11, p < 0.0001). Conversely, protective associations were found for mild physical activity (OR: 0.54, 95% CI: 0.34–0.86, p = 0.009) and light-to-moderate alcohol consumption (OR: 0.63, 95% CI: 0.42–0.95, p = 0.028), while other factors did not significantly predict dementia risk.

Conclusion: In this study, depressive symptoms and low educational attainment were independently associated with higher odds of screening-defined cognitive impairment, while mild physical activity was associated with lower odds. These findings support context-specific dementia risk reduction strategies centred on mental health, education, and healthy ageing in primary care.