Epidemiology of dementia in Central Africa : Mortality and incidence among Congolese population

Abstract

The African population is ageing at an unprecedented rate. In sub-Saharan Africa (SSA), the number of people aged 60 years and above is projected to rise to over 67 million by 2030 (representing a 100% increase in the 25 years since 2005). Incidence and mortality data help us understand the epidemiology and disease burden of dementia, and thereby improve policy planning. Although dementia prevalence have been reported for many countries of SSA, incidence and mortality related to dementia remain poorly described to date as only Nigeria had reported dementia incidence among older African adults. This study aimed to assess the dementia related incidence and mortality, and associated risk factors in Congolese people aged over 65 years recruited in EPIDEMCA survey. The baseline population was followed up during two years. Older participants were traced and interviewed annually in rural and urban Congo between 2012 and 2014. DSM-IV and NINCDS-ADRDA criteria were required for dementia and Alzheimer’s disease diagnoses. Data on vital status were collected throughout the follow-up. Cox proportional hazards model was used to assess the link between baseline dementia diagnosis and mortality risk. Risk factors for incident dementia were examined using a competing-risks regression model based on Fine and Gray methods. After two years of follow-up, 101 (9.8%) participants had died. Compared to participants with normal cognition at baseline, mortality risk was more than 2.5 times higher among those with dementia (HR= 2.53, 95% CI: 1.42-4.49, p=0.001). Among those with dementia, only clinical severity of dementia was associated with an additional increased mortality risk (HR=1.91; CI 95%, 1.23-2.96; p=0.004). Age (per 5-year increase), male sex and living in an urban area were independently associated with increased mortality risk across the full cohort. Among the dementia-free cohort, the crude incidence of dementia was estimated at 15.79 (95% CI 10.25 – 23.32) p