Association between vitamin D and respiratory outcomes in Canadian adolescents and adults

Abstract

Background: Asthma is one of the most prevalent chronic diseases worldwide, affecting more than 200 million people. Vitamin D deficiency has been reported among individuals with asthma and might play a role in asthma exacerbations. In this cross-sectional study, we investigated the association of serum 25-hydroxy vitamin D [25(OH)D] levels and current asthma, ever asthma, and lung function. Methods: Data from 3937 subjects aged 13–69 years who participated in the Canadian Health Measures Survey – Cycle 1 were considered in this study. Serum 25(OH)D levels were categorized into ≤49 nmol/L (low), 50–74 nmol/L (moderate) and ≥75 nmol/L (high). Results: The proportion of subjects with current and ever asthma was greater in the lower 25(OH)D category than in moderate and high categories. After adjusting for potential confounders, subjects in the low 25(OH)D levels were more likely to have current asthma than those in the moderate levels (OR: 1.54, 95% CI: 1.01–2.36). Low 25(OH)D levels were also associated with ever asthma (OR: 2.12, 95% CI: 1.40–3.21) among those with a family history of asthma and this association was stronger in those with asthma onset before 20 years of age. High 25(OH)D levels were associated with lower mean value of FEV₁/FVC ratio. No significant association was observed between 25(OH)D levels and other lung function measurements. Conclusion: In this study, 25(OH)D levels below 50 nmol/L were associated with an increased risk of current and ever asthma. Further exploration of this relationship is needed to determine the optimal level of vitamin D in the management of asthma in adolescents and adults.

• Asthma
• family history
• lung function
• serum 25-hydroxy vitamin D

Acknowledgements

The research and analysis are based on the data from Statistics Canada and opinions expressed herein do not represent the views of Statistics Canada.

Declaration of interest

The authors report that they have no conflicts of interest. The authors alone are responsible for the content and writing of the paper.