Vitamin D deficiency has a negative impact on lung function in children with corticosteroid-treated asthma and in adult smokers, two separate studies reported.
Vitamin D deficiency is associated with poor lung function in children with corticosteroid-treated asthma and in adult smokers, according to two separate studies published online ahead of print by the American Journal of Respiratory and Critical Care Medicine.
Ann Chen Wu, MD, MPH, and colleagues of Harvard Medical School and Harvard Pilgrim Health Care, Boston, assessed the effects of vitamin D levels in children with persistent, corticosteroid-treated asthma in a study published July 12. Nancy E. Lange, MD, MPH, and colleagues of Brigham and Women’s Hospital in Boston, examined the effects of vitamin D deficiency and smoking on lung function and the rate of lung function decline in a study published July 19.
Hindering Corticosteroid Response
In the asthma study, Wu and colleagues measured 23-hydroxyvitamin D levels in the serum of 1,024 children ages 5 to 12 with mild to moderate persistent asthma. Data were collected from the Childhood Asthma Management Program, a multicenter trial in which children were randomly assigned to treatment with budesonide (an inhaled corticosteroid), nedocromil, or placebo. The children were characterized as having vitamin D sufficiency (serum levels > 30 ng/mL), insufficiency (serum levels of 20 to 30 ng/mL), or deficiency (serum levels of ≤ 20 ng/mL). The researchers looked for associations between vitamin D status and changes from enrollment to follow-up at eight to 12 months in prebronchodilator FEV1, bronchodilator response to inhaled β-agonists (BDR), and responsiveness to provocative concentration of methacholine producing a 20% decline in FEV1 (PC20). Their analyses adjusted for age, sex, race, BMI, history of emergency department visits, and season when the vitamin D specimen was drawn.
At baseline, 65% of subjects were vitamin D sufficient, 25% were vitamin D insufficient, and 10% were vitamin D deficient. Compared with the other subjects, those with vitamin D deficiency were more likely to be older, to be African American, and to have higher BMI. Vitamin D deficiency was found among 7%, 12%, and 11% of subjects treated with corticosteroids, nedocromil, and placebo, respectively.
At follow-up, there were no differences in prebronchodilator FEV1, BDR, or PC20 according to vitamin D group within the entire cohort or within treatment groups. Furthermore, the vitamin D groups had no differences in lung function changes from baseline to follow-up when all treatment groups were combined.
Among patients treated with corticosteroids, however, improvements from baseline to follow-up differed according to vitamin D status. For these patients, prebronchodilator FEV1 increased by 140 mL, 330 mL, and 290 mL in those with vitamin D deficiency, vitamin D insufficiency, and vitamin D sufficiency, respectively. In an adjusted analysis, both vitamin D sufficiency and insufficiency were associated with greater changes in prebronchodilator FEV1, compared with vitamin D deficiency, in corticosteroid-treated patients.
The study had some limitations, including the small sample of vitamin D–deficient children and the fact that vitamin D levels were studied only at one time point, the researchers noted. Nevertheless, they said, their findings suggest that vitamin D supplementation may enhance the anti-inflammatory function of corticosteroids in patients with asthma.
“Our study is the first to suggest that vitamin D sufficiency in asthmatic children treated with inhaled corticosteroids is associated with improved lung function,” Wu added. “Accordingly, vitamin D levels should be monitored in patients with persistent asthma being treated with inhaled corticosteroids. If vitamin D levels are low, supplementation with vitamin D should be considered.”
Increasing Smokers’ Decline
In an ongoing longitudinal study, Lange and colleagues analyzed data on 626 adult white men, both smokers and nonsmokers, from the Normative Aging Study. At three different times—the first occurring from 1984 to 1989, the second from 1992 to 1999, and the third from 1995 to 2003—the participants had concurrent assessments of lung function (via spirometry) and vitamin D levels. The researchers defined vitamin D deficiency as serum levels of 20 ng/mL or lower.
The participants had a mean age of 59.9 at Time 1, 66.5 at Time 2, and 73.3 at Time 3. During those periods, 10%, 5%, and 4% of the participants were current smokers, and vitamin D deficiency was present in 45%, 18%, and 25% of participants, respectively.
Overall, vitamin D deficiency did not affect lung function or lung function decline significantly. However, there was a mean reduction of 12 mL in FEV1 for each one-unit increase in pack-years of smoking in subjects with vitamin D deficiency, compared with a mean reduction of 6.5 mL per one-unit increase in pack-years among subjects who were not vitamin D deficient. Longitudinal models showed that, over time, vitamin D deficiency exacerbated the effect of smoking pack-years on FEV1 decline.
“Our results suggest that vitamin D might modify the damaging effects of smoking on lung function,” Lange said. “These effects might be due to vitamin D’s anti-inflammatory and anti-oxidant properties.
“If these results can be replicated in other studies, they could be of great public health importance,” he added. “Future research should also examine whether vitamin D protects against lung damage from other sources, such as air pollution.”
Despite the study’s findings, “the health hazards associated with smoking far outweigh any protective effect that vitamin D may have on lung function,” emphasized Alexander C. White, MS, MD, Chair of the American Thoracic Society’s Tobacco Action Committee. “First and foremost, patients who smoke should be fully informed about the health consequences of smoking and in addition be given all possible assistance to help them quit smoking.”
Lange NE, Sparrow D, Vokonas P, Litonjua AA. Vitamin D deficiency, smoking, and lung function in the normative aging study. Am J Respir Crit Care Med. 2012 Jul 19; [Epub ahead of print]. Wu AC, Tantisira K, Li L, et al; the Childhood Asthma Management Program Research Group.The effect of vitamin D and inhaled corticosteroid treatment on lung function in children. Am J Respir Crit Care Med. 2012 Jul 12; [Epub ahead of print].