The joint effect of vitamin-D status and tobacco exposure on overweight and obesity in children.

This study aimed to explore the combined effects of serum vitamin-D level and tobacco exposure on the risk of overweight and obesity in children. This cross-sectional study analysed the data of 11 636 children aged 2-17 years from the National Health and Nutrition Examination Surveys database between 2007 and 2018. Univariable and multivariate weighted logistic regression models were used to analyse the associations of serum vitamin-D or cotinine levels with overweight and obesity in children as well as the combined effects of serum vitamin-D and cotinine on the risk of overweight and obesity in children. Subgroup analysis was performed in terms of gender, age, race and household smokers. OR with corresponding 95 % CI was presented. The elevated risk of overweight and obesity in children was found in those with serum vitamin-D < 20 ng/ml (OR = 1·44, 95 % CI: 1·29, 1·61). Also, the odds of overweight and obesity in children was 1·14 (OR = 1·14, 95 % CI: 1·01, 1·29) in children with cotinine ≥ 0·05 ng/ml. Relative to participants with serum vitamin-D ≥ 20 ng/ml and cotinine < 0·05 ng/ml, increased risk of overweight and obesity was identified in those with serum vitamin-D < 20 ng/ml and cotinine < 0·05 ng/ml (OR = 1·45, 95 % CI: 1·26, 1·68) and serum vitamin-D < 20 ng/ml and cotinine ≥ 0·05 ng/ml (OR = 1·62, 95 % CI: 1·38, 1·91). Serum vitamin-D and cotinine exposure had combined effects on the risk of overweight and obesity in children.