Vitamin D Insufficiency and Asthma in a US Nationwide Study.

BACKGROUND: Vitamin D insufficiency (a serum 25-hydroxy vitamin D level of <30 ng/mL) has been associated with asthma morbidity.

OBJECTIVE: To examine vitamin D insufficiency, asthma, and lung function among US children and adults.

METHODS: Using data from the National Health and Nutrition Examination Survey from 2001 to 2010, we examined vitamin D insufficiency and (1) current asthma or wheeze in 10,860 children (6-17 years) and 24,115 adults (18-79 years) and (2) lung function in a subset of participants. Logistic or linear regression was used for the multivariable analysis, adjusting for age, sex, race/ethnicity, income, body mass index, smoking, and C-reactive protein level.

RESULTS: Vitamin D insufficiency was associated with current asthma (odds ratio, 1.35; 95% CI, 1.11-1.64) and current wheeze in children, as well as with current wheeze in adults (odds ratio, 1.17; 95% CI, 1.04-1.31). After stratifying the analysis by race/ethnicity and (in adults) current smoking, vitamin D insufficiency was associated with current asthma and wheeze in non-Hispanic white children only; in adults, vitamin D insufficiency was associated with current wheeze in non-Hispanic whites and blacks. Vitamin D insufficiency was also associated with lower FEV1 and forced vital capacity in children and adults. When analyzing each National Health and Nutrition Examination Survey wave separately, vitamin D insufficiency prevalence was 72% to 76% from 2001 to 2006, and then decreased from 2007 to 2010 (64%-65%); interestingly, asthma prevalence decreased for the first time from the period 2007 to 2008 (8.2%) to the period 2009 to 2010 (7.4%).

CONCLUSIONS: We show racial/ethnic-specific associations between vitamin D insufficiency and current asthma or wheeze in children and adults. Moreover, we report parallel recent decrements in the prevalence of vitamin D insufficiency and asthma.