Prevalence of dementia in Nigeria: a systematic review of the evidence

Abstract

Background: The burden of dementia is poorly understood in Nigeria. We sought to gather available epidemiologic evidence on dementia in Nigeria to provide country-wide estimates of its prevalence and associated risks. Methods: We searched MEDLINE, EMBASE, Global Health, Africa Journals Online (AJOL) and Google Scholar for epidemiologic studies on dementia in Nigeria from 1990 to 2018. We pooled crude estimates using random effects meta-analysis. A meta-regression epidemiologic model, using the United Nations demographics for Nigeria, was used to estimate the absolute number of people living with dementia in Nigeria in 1995 and 2015. Results: Our searches returned 835 studies, of which nine were selected. These included 10 820 individuals with a median age of 74.4 years. Heterogeneity (I2=98.8%, P<0.001) was high across studies. Five studies were conducted in the South-west, and four studies were rated as high quality. The pooled crude prevalence of dementia in Nigeria was 4.9% (95% CI: 3.0–6.9) with prevalence significantly higher in women (6.7%, 3.6–9.9) compared to men (3.1%, 1.2–5.0). Age 80+ (odds ratio (OR) 1.6, 1.3–1.9), female sex (OR 2.2, 1.4–3.4) and BMI ≤18.5 (OR 3.5, 1.2–10.1) were significant risks for dementia in Nigeria. Using our epidemiologic model, we estimated that the number of dementia cases increased by over 400% over a 20-year period, increasing from 63 512 in 1995 to 318 011 in 2015 among persons aged ≥60 years. Conclusion: Our findings suggest the prevalence and cases of dementia have increased in Nigeria over the last two decades. Population-wide response to dementia is lacking.

Incidence of Cognitive Impairment during Aging in Rural South Africa: Evidence from HAALSI, 2014 to 2019

“…These discrepant results could be due to true population differences in incidence, or artificial differences induced by different outcome classification criteria or study methodologies. Our findings are consistent with cross-sectional studies associating low education and illiteracy with higher prevalence of cognitive impairment and dementia in South Africa and other sub-Saharan African countries but inconsistent with those identifying sex/gender-based disparities [7-9, 13, 27, 39-41]. Our results are mostly consistent with a longitudinal study of cognitive decline over 2 years among adults aged 65 and over in a rural Tanzania [42].…”

Prevalence estimates of dementia in older adults in rural Kilimanjaro 2009–2010 and 2018–2019: is there evidence of changing prevalence?

“…Both our 2009–2010 and 2018–2019 estimates are substantially higher than estimates from Nigeria, where the great majority of previous epidemiological studies of dementia in SSA have taken place. Reviews of these West African epidemiological data suggest that dementia prevalence remains consistently low, but that there has been no evidence of a decline over time, in contrast to studies of African‐Americans using similar methodology 7,10 . It is not yet clear why the prevalence in Tanzania appears higher than in Nigeria, given that prevalence appears similar to that reported in other SSA settings 35–37,45 .…”

“…In sub‐Saharan Africa (SSA), epidemiological data on dementia have been limited and only recently have sufficient data been available to allow meta‐analysis of prevalence with acceptable precision 8 . Reviews based on these data suggest that 2.1 million people are affected and that dementia prevalence may be increasing 7,9,10 . However, it is not clear to what extent this reflects refinements of research methodology and culture‐specific dementia assessment.…”

“We Are Doing These Things So That People Will Not Laugh at Us”: Caregivers’ Attitudes About Dementia and Caregiving in Nigeria

“…Like most countries, Nigeria is experiencing rapid population aging and an increase in the prevalence of Alzheimer’s disease (AD) and related dementias (hereafter referred to as dementia; Ballard et al, 2011; Kalaria et al, 2008; Sosa-Ortiz et al, 2012). The pooled prevalence of all dementias in Nigeria from 1990 through 2018 was estimated at 4.9%, with men showing higher rates (6.7%) compared with women (3.9%; Adeloye et al, 2019). According to George-Carey et al (2012), dementia prevalence likely doubles every 5 years after age 65, which will lead to increases in Nigeria as the population ages.…”