Abstract
Background: The vitamin D status of African populations remains inadequately characterized. Our objective was to estimate the prevalence of vitamin D deficiency in children and adults living in Africa. Methods: We searched PubMed/MEDLINE, Web of Science, Embase, African Journals Online and African Index Medicus for published vitamin D prevalence studies without language restriction. We included all studies with measured serum 25-hydroxyvitamin D (25(OH)D) concentrations from healthy participants residing in Africa. We conducted meta-analyses to derive the pooled prevalence of vitamin D deficiency using established cut-offs and mean 25(OH)D concentrations. We stratified by participant age group (adults vs. children) and area of residence (urban vs. rural). The study protocol was registered with PROSPERO (number CRD42018112030). Findings: One hundred and thirteen studies with 19,380 participants from 21 African countries were included in the meta-analysis. The pooled prevalence of low vitamin D status was 57·6% (95% CI 48·4, 66·6), 39·3% (95% CI 30·8, 48·3) and 25·1% (95% CI 15·9, 35·6) for cut-offs of <75 nmol/L, <50 nmol/L, and <30 nmol/L respectively. The overall mean 25(OH)D concentration was 69·1 nmol/L (95% CI 65·4, 72·8). Vitamin D levels were relatively lower in populations living further from the equator, in women, children, and in urban areas. Interpretation: The prevalence of vitamin D deficiency is high in African populations. Public health strategies should include efforts to prevent, detect and treat vitamin D deficiency, especially in vulnerable populations. Funding: This work was funded by Wellcome (grants 110255/Z/15/Z to SHA, 202800/Z/16/Z to TNW and the DELTAS Africa Initiative (DEL-15-003). Declaration of Interest: We declare no competing interests. Ethical Approval: The study protocol was registered with PROSPERO (number CRD42018112030).
Highlights
Vitamin D deficiency is reported worldwide[1] and has been associated with non-communicable and infectious diseases.[2]
Individuals of African ancestry living in temperate regions have a poorer vitamin D status than do other ethnicities, which has been associated with higher prevalence of cardiovascular disease, diabetes, and some cancers observed among African–American people.[5]
129 studies with 21 474 participants from 23 African countries were included in the systematic review. 119 of these studies were included in the metaanalysis
Summary
Vitamin D deficiency is reported worldwide[1] and has been associated with non-communicable and infectious diseases.[2]. A 2014 report by WHO estimates that the burden of non-communicable diseases will overtake that of communicable diseases in Africa by 2030, a trend that has been attributed to lifestyle changes related to rapid urbanisation.[3,4] Individuals of African ancestry living in temperate regions have a poorer vitamin D status than do other ethnicities, which has been associated with higher prevalence of cardiovascular disease, diabetes, and some cancers observed among African–American people.[5] The presence of vitamin D receptors in most tissues and cells and the regulation of more than 200 human genes by vitamin D suggest that vitamin D could have diverse roles in maintaining health.[6,7]. Rickets and osteomalacia caused by vitamin D deficiency are considered unlikely at concentrations higher than
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