Prevalence estimates of major neurocognitive disorders in a rural Nigerian community

There is paucity of information on major neurocognitive disorders in sub-Saharan Africa where the number of individuals with neurocognitive disorders is expected to increase due to demographic transition. This study aims to report on the prevalence estimates of dementia and MCI (mild cognitive impairment) in a rural community in southwest Nigeria.

This was a two-stage cross-sectional study of persons aged 65 years and above resident in Lalupon community, Oyo State. The Identification and IDEA (Intervention for Dementia in Elderly Africans) Study Questionnaire was used for initial screening by trained community health care workers, utilized followed by cognitive assessment using the validated IDEA cognitive screen. Functional and cognitive assessment of selected individuals was carried out during the second stage. Information obtained was used for consensus diagnosis and participants were categorized into normal, MCI and dementia using standard criteria.

Six hundred and thirteen participants completed the study with 111 (18.1%) diagnosed as MCI while 17 (2.8%) had dementia. The age-adjusted prevalence estimates were 18.4% (95% CI: 14.9-21.9%) and 2.9% (95% CI 1.6-4.4%) for MCI and dementia, respectively. Probable Alzheimer's disease and amnestic MCI predominated. Individuals with dementia were older than both MCI and normal cases while those with MCI had significantly fewer years of schooling than the other diagnostic categories.

Almost one out of five older persons in Lalupon community had major neurocognitive impairment with MCI being six-times more common than dementia. Alzheimer's disease was the most common dementia sub-type.