Vitamin D deficiency in northern Vietnam: prevalence, risk factors and associations with bone mineral density.

PURPOSE: Vitamin D deficiency has been linked to osteoporosis and also to the risk of cancer, autoimmune disorders and cardiovascular diseases. This study sought to determine the prevalence of, and risk factors for, vitamin D deficiency and its relationship with bone mineral density (BMD) in a Vietnamese population.
METHODS: This cross-sectional study involved 269 women and 222 men aged 13-83 years, who were randomly selected from urban and rural areas in northern Vietnam. Serum concentrations of 25-hydroxy-vitamin D [25(OH)D] and parathyroid hormone (PTH) were measured by electrochemiluminescence immunoassay. Vitamin D deficiency was defined as serum 25(OH)D levels below 20 ng/mL. BMD was measured by dual X-ray absorptiometry.
RESULTS: The prevalence of vitamin D deficiency in women was 30%, almost two-fold higher than in men (16%). Significant predictors of vitamin D deficiency in women were urban residency (p<0.01) and age less than 30 years (p<0.01), whereas use of contraceptive pills was protective (p<0.01). In men, winter season was the only significant predictor of vitamin D deficiency (p<0.01). In multiple linear regression analysis, serum levels of 25(OH)D were positively associated with BMD in both women (p<0.001) and men (p<0.001).
CONCLUSIONS: These data suggest that the prevalence of vitamin D deficiency is high in the Vietnamese population, and that part of this prevalence could be explained by low exposure to sunlight (urban residency and winter season). The high prevalence of vitamin D deficiency should raise the awareness of potentially important health issues such as osteoporosis within the Vietnamese society.