Challenges in estimating the prevalence of vitamin D deficiency in Africa – Authors' reply
Authors: Reagan M Mogire, Sarah H Atkinson
Journal: The Lancet Global Health (2022)

We thank Aiyong Cui and colleagues for their interest in our systematic review of vitamin D deficiency in Africa.1Mogire RM Mutua A Kimita W et al.Prevalence of vitamin D deficiency in Africa: a systematic review and meta-analysis.Lancet Glob Health. 2020; 8: e134-e142Summary Full Text Full Text PDF PubMed Scopus (79) Google Scholar Cui and colleagues identified three studies in which we mistakenly included the recruited number of participants rather than the number with vitamin D measurements (PMID 24605693, 30822819, and 31159206). Correcting these mistakes did not alter prevalence estimates in the revised meta-analyses. Cui and colleagues also identified data extraction errors for three studies, which changed prevalence estimates. In two studies, we mistakenly misclassified participant subgroups (PMID 30866564 and 26070223), and in a third study (PMID 30375272), we made an error in extracting the prevalence of vitamin D deficiency, defined as 25-hydroxyvitamin D (25[OH]D) of less than 50 nmol/L, which resulted in minor changes to overall and subgroup estimates (table). In our initial study design, we considered using 25(OH)D concentrations of 30–50 nmol/L, 50–75 nmol/L, and 75–150 nmol/L, as suggested by Cui colleagues, but few studies from Africa included these cutoffs.TableCorrections to estimates of prevalence of vitamin D deficiency and mean 25(OH)D concentrationOverallNewborn babiesChildrenAdults (non-pregnant)Pregnant womenPrevalence of vitamin D deficiency by 25(OH)D cutoff, % (95% CI)<50 nmol/LPrevious estimate34·22% (26·22–42·68)49·07% (24·88–73·49)22·99% (12·03–36·14)35·62% (24·56–47·50)43·91% (15·14–75·07)Revised estimate34·18% (26·30–42·51)49·07% (24·88–73·49)25·38% (13·71–39·12)33·96% (23·13–45·69)43·50% (17·18–71·92)<30 nmol/LPrevious estimate18·46% (10·66–27·78)63·72% (9·20–100·00)10·55% (3·25–21·14)12·59% (4·83–23·16)52·86% (5·90–96·64)Revised estimate17·31% (9·86–26·27)63·72% (9·20–100·00)10·55% (3·25–21·14)12·58% (4·83–23·16)33·29% (1·66–78·50)<75 nmol/LPrevious estimate58·83% (50·90–66·54)76·78% (23·65–100·00)46·42% (31·86–61·28)59·35% (49·85–68·51)79·20% (40·28–99·90)Revised estimate58·54% (50·23–66·62)76·78% (23·65–100·00)44·19% (29·41–59·51)61·37% (51·54–70·76)68·62% (28·19–97·12)Mean 25(OH)D concentration, nmol/L (95% CI)Previous estimate67·62 (64·36–70·88)50·60 (38·91–62·29)72·22 (64·89–79·54)69·04 (64·52–73·57)65·73 (45·65–85·81)Revised estimate68·10 (64·83–71·37)50·60 (38·91–62·29)72·22 (64·87–79·57)69·38 (64·82–73·94)68·46 (49·91–87·01)25(OH)D=25-hydroxyvitamin D. Open table in a new tab 25(OH)D=25-hydroxyvitamin D. We took the opportunity to repeat our searches and analyses and identified an additional study by Laird and colleagues2Laird E Thurston SW van Wijngaarden E et al.Maternal vitamin D status and the relationship with neonatal anthropometric and childhood neurodevelopmental outcomes: results from the Seychelles Child Development Nutrition Study.Nutrients. 2017; 91235Crossref PubMed Scopus (18) Google Scholar from the Seychelles, which was not included in our original publication. We have added estimates from that study, in addition to the corrections suggested by Cui and colleagues, to the final corrected manuscript. After correcting our meta-analyses by addressing the errors highlighted by Cui and colleagues and adding the study by Laird and colleagues, the overall prevalence of vitamin D deficiency, as defined by 25(OH)D levels of less than 50 nmol/L, was revised from 34·22% to 34·18%; the prevalence as defined by 25(OH)D of less than 30 nmol/L was revised from 18·46% to 17·31%; and the prevalence as defined by 25(OH)D of less than 75 nmol/L was revised from 58·83% to 58·54% (table). Some prevalence estimates by subgroup, and the estimates of mean 25(OH)D concentration overall and in some subgroups, were also revised (table). The conclusions of our study remain unchanged after implementing these corrections. We declare no competing interests. Challenges in estimating the prevalence of vitamin D deficiency in AfricaWe read with great interest the study by Reagan Mogire and colleagues1 in The Lancet Global Health estimating the prevalence of vitamin D deficiency in Africa. Of 119 articles included in the meta-analysis, we are interested in 30 of them and have discovered data extraction errors that greatly affect the reliability of research results in 11 articles. Full-Text PDF Open AccessPrevalence of vitamin D deficiency in Africa: a systematic review and meta-analysisThe prevalence of vitamin D deficiency is high in African populations. Public health strategies in Africa should include efforts to prevent, detect, and treat vitamin D deficiency, especially in newborn babies, women, and urban populations. Full-Text PDF Open Access