Serum 25-hydroxy-vitamin D and ionised calcium in relation to lung function and allergen skin tests.

BACKGROUND

Evidence suggests that higher levels of vitamin D and calcium are associated with greater lung function and that vitamin D is inversely associated with atopic sensitisation. It is unknown whether the associations of vitamin D and calcium with lung function are independent of each other or mediated by atopic sensitisation.

OBJECTIVE

To study the associations of 25-hydroxyvitamin D (25(OH)D) and ionised calcium levels with lung function and specific allergen sensitisation in adolescents (12-19 years) and adults (20-59 years) and to assess whether the associations with lung function are due to altered atopic sensitisation.

METHODS

This is a cross-sectional analysis of the data from the third National Health and Nutrition Examination Survey.

RESULTS

The 25(OH)D levels were positively associated with forced vital capacity in adolescents (0.035 (95% confidence interval (CI): 0.007-0.064) s.d.; s.d. in model adjusted for multiple confounders). This association and the previously reported association between higher serum levels of 25(OH)D and better lung function in adults were independent of serum calcium levels, which were not associated with lung function. In adults, calcium was associated with sensitisation to grass allergens (odds ratio per s.d., 1.17 (95% CI: 1.03-1.32), 1.15 (95% CI: 1.01-1.31) and 1.18 (95% CI: 1.06-1.32) for white oak, Bermuda grass and short ragweed, respectively) and peanut odds ratio 1.21 (95% CI: 1.02-1.43) after adjusting for age, gender and race/ethnicity, but these associations attenuated towards the null after adjusting for additional confounders. The associations were independent of 25(OH)D levels, which were not associated with allergen sensitisation.

CONCLUSIONS

Circulating levels of 25(OH)D are positively associated with lung function and this does not seem to be driven by allergen sensitisation or influenced by calcium levels.