Journal
AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE
Volume 186, Issue 7, Pages 616-621Publisher
AMER THORACIC SOC
DOI: 10.1164/rccm.201110-1868OC
Keywords
vitamin D; vitamin D deficiency; lung function decline; smoking; effect modification
Categories
Funding
- National Institutes of Health [R21 HL089842, R01 AG027014, T32 HL007427]
- Cooperative Studies Program/Epidemiology Research and Information Center of the U.S. Department of Veterans Affairs
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Rationale: Vitamin D has immunomodulatory and antiinflammatory effects that may be modified by cigarette smoke and may affect lung function. Objectives: To examine the effect of vitamin D deficiency and smoking on lung function and lung function decline. Methods: A total of 626 men from the Normative Aging Study had 25-hydroxyvitamin D levels measured at three different times between 1984 and 2003 with concurrent spirometry. Vitamin D deficiency was defined as serum level <= 20 ng/ml. Statistical analysis was performed using multivariable linear regression and mixed effects models. Measurements and Main Results: In the overall cohort, there was no significant effect of vitamin D deficiency on lung function or on lung function decline. In both cross-sectional and longitudinal multivariable models, there was effect modification by vitamin D status on the association between smoking and lung function. Cross-sectional analysis revealed lower lung function in current smokers with vitamin D deficiency (FEV1, FVC, and FEV1/FVC; P <= 0.0002), and longitudinal analysis showed more rapid rates of decline in FEV1 (P = 0.023) per pack-year of smoking in subjects with vitamin D deficiency as compared with subjects who were vitamin D sufficient. Conclusions: Vitamin D deficiency was associated with lower lung function and more rapid lung function decline in smokers over 20 years in this longitudinal cohort of elderly men. This suggests that vitamin D sufficiency may have a protective effect against the damaging effects of smoking on lung function. Future studies should seek to confirm this finding in the context of smoking and other exposures that affect lung function.
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