Plasma 25-hydroxyvitamin D associated with pulmonary function in Canadian adults with excess adiposity.

Background: Vitamin D deficiency is an important health issue, particularly among people residing in northern countries. Low concentrations of 25-hydroxyvitamin D [25(OH)D] have been linked to several health conditions. Objective: The objective was to determine the association between plasma 25(OH)D and pulmonary function and the effect modifications of sex and body mass index (BMI) in adults. Design: A cross-sectional study included 3359 adults aged ≥18 y who participated in the Canadian Health Measures Survey, and a 2-stage multiple linear regression analysis was conducted. Results: Overall, 26% of the adults had a plasma 25(OH)D concentration <50 nmol/L, which is considered deficient (ie, hypovitaminosis D). This deficiency was more prevalent among men than among women (30% compared with 23%). Regression analysis showed that deficient plasma 25(OH)D was associated with lower mean residual forced vital capacity and forced expiratory volume in 1 s in men after adjustment for covariates. When further stratified by BMI, the associations were more marked in overweight and obese men. Vitamin D deficiency associated with pulmonary function was not statistically significant in normal-weight men or in women, regardless of BMI categories. Similar results were obtained when plasma 25(OH)D was examined as a continuous variable in the models. Conclusions: Hypovitaminosis D may be a risk factor for lung dysfunction, especially for overweight and obese men. Further research is necessary to determine the mechanism of the interrelation between vitamin D, adiposity, and pulmonary function. [ABSTRACT FROM AUTHOR]