Challenges in estimating the prevalence of vitamin D deficiency in Africa
Authors: Aiyong Cui, Yuzhuo Ma, Mengli Xie, Simin Wang, Junqing Shen, Lei Yang, Chen Fei, Feng Qiao
Journal: The Lancet Global Health (2022)

We read with great interest the study by Reagan Mogire and colleagues1Mogire 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 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. When estimating the prevalence of vitamin D deficiency with a cutoff of serum 25-hydroxyvitamin D (25[OH]D) less than 50 nmol/L in the subgroup of adults (non-pregnant), the study by Botros and colleagues2Botros RM Sabry IM Abdelbaky RS Eid YM Nasr MS Hendawy LM Vitamin D deficiency among healthy Egyptian females.Endocrinol Nutr. 2015; 62: 314-321Crossref PubMed Scopus (37) Google Scholar reported that the total number of women with vitamin D deficiency was 273, of whom 27 were pregnant women. However, the author extracted and used 273 to estimate the vitamin D deficiency in non-pregnant women. Similar errors occurred in other studies. For example, Bodin and colleagues3Bodin J Mihret A Holm-Hansen C et al.Vitamin D deficiency is associated with increased use of antimicrobials among preschool girls in Ethiopia.Nutrients. 2019; 11: 575Crossref Scopus (3) Google Scholar included preschool children as participants, but Mogire and colleagues used those data to estimate vitamin D deficiency in adults (non-pregnant). When estimating the prevalence of vitamin D deficiency with a cutoff of serum 25(OH)D concentration less than 50 nmol/L in the subgroup of children, the study by Poopedi and colleagues4Poopedi MA Norris SA Pettifor JM Factors influencing the vitamin D status of 10-year-old urban South African children.Public Health Nutr. 2011; 14: 334-339Crossref PubMed Scopus (43) Google Scholar reported that the number of people with vitamin D deficiency was 27 with a sample size of 385. However, Mogire and colleagues extracted data for 65 participants with a sample size of 295. The study by White and colleagues5White Z White S Dalvie T Kruger MC Van Zyl A Becker P Bone health, body composition, and vitamin D status of black preadolescent children in South Africa.Nutrients. 2019; 111243Crossref Scopus (8) Google Scholar had 84 participants, of whom 59 agreed to have their blood analysed for the vitamin D assessment, but Mogire and colleagues used 84 as the sample size to estimate vitamin D deficiency. When estimating the prevalence of vitamin D deficiency with a cutoff of serum 25(OH)D concentration less than 30 nmol/L in the subgroup of adults (non-pregnant), the sample size in the study by Gebreegziabher and colleagues6Gebreegziabher T Stoecker BJ Vitamin D insufficiency in a sunshine-sufficient area: southern Ethiopia.Food Nutr Bull. 2013; 34: 429-433Crossref PubMed Scopus (28) Google Scholar was 196, of which 29 participants were deficient in vitamin D, whereas the sample size extracted by the authors was 202, with 30 having vitamin D deficiency. We respectfully thank Mogire and colleagues for providing us with this valuable work. Nevertheless, considering the large number of errors in extracting data, further corrections with more accurate data are warranted to elucidate the prevalence of vitamin D deficiency in Africa. Additionally, future meta-analyses to assess vitamin D levels in different ranges will be meaningful to understand vitamin D status (eg, <30 nmol/L, 30–50 nmol/L, >50 nmol/L, 50–75 nmol/L, >75 nmol/L, 75–150 nmol/L, and >150 nmol/L). Furthermore, to perform the meta-analyses more accurately, we should abide by the principle that at least two authors extract the data and check each other's work. In addition, some authors of the original articles should be selected as peer reviewers to find out whether the extracted data are accurate. We declare no competing interests. AC, YM, MX, and SW contributed equally to this work. Challenges in estimating the prevalence of vitamin D deficiency in Africa – Authors' replyWe thank Aiyong Cui and colleagues for their interest in our systematic review of vitamin D deficiency in Africa.1 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. 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