Prevalence of vitamin D deficiency and related factors among adults in Tokat province, Türkiye: a community-based cross-sectional study.

Background: Vitamin D deficiency is a major public health concern, worldwide yet data on the adult population in Türkiye remain limited. This study aimed to determine the prevalence of vitamin D deficiency and its associated risk factors in Tokat Province, Türkiye. Methods: A population based cross-sectional study was conducted among 2,225 adults aged ≥20 years through multistage stratified cluster sampling from both urban and rural areas. Data were obtained via structured questionnaires, anthropometric measurements, and fasting blood samples. Serum 25-hydroxyvitamin D3 [25(OH)D3] levels were measured and categorized as deficient (<10 ng/mL), insufficient (10-20 ng/mL), or sufficient (>20 ng/mL). Multivariate logistic regression was used to identify predictors of deficiency. Results: The mean age was 47.2 ± 15.2 years, and 54.8% were women. Vitamin D deficiency was present in 38.7% and insufficiency in 46.4% of participants. Deficiency was significantly more common among women, the older adult, obese individuals, and those with lower education levels and chronic diseases (p < 0.05). In the adjusted model female sex (aOR 0.19, 95% CI 0.14-0.27), obesity (aOR 1.76, 95% CI 1.36-2.28), and lower education were independent predictors of deficiency. Conclusion: Vitamin D deficiency and insufficiency are highly prevalent among adults in Tokat Province, despite adequate sunlight exposure in the region. Public health strategies/interventions should focus on high-risk groups, prioritize particularly women, older adults, and obese individuals through screening, education, and targeted supplementation.