Low prevalence of vitamin D deficiency in adult residents in Hainan, the tropical island province of China

Background: Vitamin D deficiency is considered to be a global health problem. The purpose of this study was to evaluate the prevalence of vitamin D deficiency and analyze its related factors among adult residents in Hainan, a tropical island province of southern China.

Methods: A total of 1,700 healthy adults, aged 18-86 years (617 men and 1,073 women), were enrolled in our cross-sectional descriptive study. Binomial logistic regression analyses were performed to identify possible predictors of vitamin D status.

Results: The average serum 25-hydroxyvitamin D [25(OH)D] concentration was 37.66±10.77 ng/mL (males 43.60±11.8 ng/mL, females 34.20±8.40 ng/mL; I<0.001). The proportions of vitamin D sufficiency [25(OH)D ≥30 ng/mL], insufficiency [20 ng/mL ≤25(OH)D <30 ng/mL], and deficiency [25(OH)D <20 ng/mL] were 76.6%, 20.5%, and 2.9%, respectively. Vitamin D deficiency in the young, middle-aged, and elderly groups were 4.2%, 2.7%, and 1.7%, respectively. Vitamin D sufficiency was found to be positively associated with male sex (P<0.0001), age >40 years (P=0.014), habitation in a rural area (P<0.0001), summer/autumn seasons (P<0.0001), and having <13 years of formal education (P<0.0001).

Conclusions: Our study was the first to assess the vitamin D status and analyze related factors among adult residents in Hainan Province, China. We found that vitamin D deficiency has low prevalence in this population, suggesting that before developing a strategy for the clinical use of vitamin D supplements in a region, the levels of vitamin D in generally healthy populations of that region should be assessed, to avoid unnecessary supplementation.