Temporal and Spatial Distribution of vitamin D Deficiency worldwide as 2019- Systematic review

Background: Vitamin D deficiency is a growing global public health concern with important skeletal and extra-skeletal health consequences. Although sunlight exposure is the primary source of vitamin D, deficiency remains prevalent even in regions with abundant sunshine. This systematic review aimed to describe the temporal and spatial distribution of vitamin D deficiency worldwide as at 2019 using epidemiological and geospatial approaches. Methods: A systematic review of studies published between 1995 and 2019 was conducted using PubMed. Eligible studies included healthy adults aged ≥ 18 years and reported the prevalence of vitamin D deficiency, defined as serum 25-hydroxyvitamin D levels < 30 ng/mL (75 nmol/L). Studies involving children, pregnant women, individuals with comorbidities, or vitamin D supplementation were excluded. Data were extracted on sample size, number of deficiency cases, and prevalence with confidence intervals. Statistical analysis was performed using SPSS, while geographic distribution and predictive risk mapping were generated using ArcGIS 10.3 employing kriging interpolation. Results: A total of 144 studies from 46 countries were included, encompassing 357,089 participants, of whom 218,174 were vitamin D deficient, resulting in an overall prevalence of 51.3% (95% CI: 48.4–58.6). The highest prevalence was observed in Africa (65%) and the Middle East (63.1%), followed by Europe (56.1%), South America (53.5%), Asia (52.1%), and Australia (46.2%). North America had the lowest prevalence (23%). Geospatial analysis identified a high-risk belt extending across Europe, North Africa, Western Asia, and parts of South America. Publication trends increased markedly after 2004. Conclusion: Vitamin D deficiency is highly prevalent worldwide, including in sun-rich regions. Geospatial mapping highlights critical high-risk areas, emphasizing the need for targeted screening, prevention strategies, and public health interventions globally