title: A test of vitamin D benefits on respiratory health mediated through inflammatory markers.
abstract: Previous studies have shown that vitamin D has beneficial effects on respiratory health. The role of inflammation as a possible mediator between vitamin D and respiratory health is not well understood. We used National Health and Nutrition Examination Survey 2001-2006 data (unweighted N = 12,856) to examine the mediating effects of biomarkers of inflammation on associations between vitamin D and respiratory health. Vitamin D was measured by serum 25 hydroxy vitamin D test. Respiratory health was measured by self-reported respiratory symptoms and chronic obstructive pulmonary disease (COPD). Biomarkers included C-reactive protein (CRP), alkaline phosphatase (AP), and five leukocyte measures. Models controlled for season, age, sex, race/ethnicity, body mass index, and current and former smoking. Lower levels of vitamin D were significantly associated with respiratory symptoms (linear trend p < 0.01) and with COPD (linear trend p < 0.0002) after adjusting for covariates. Adding biomarkers to the models to test for mediation, the vitamin D effect on respiratory health was not a consequence of any single marker but was partially attenuated as a combined result of leukocytes, AP, and CRP. Vitamin D is beneficial to improve respiratory health. Its benefits do not appear to be mediated by any single biomarker examined in this study; rather, benefits of vitamin D may act broadly through multiple mediating mechanisms.
authors.affiliation: Department of Applied Health Science, School of Public Health, Indiana University, Bloomington, IN, USA hendryx@indiana.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Hendryx
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Indiana University, Bloomington, IN, USA.
authors.forename: Juhua
authors.initials: J
authors.lastname: Luo
mesh_terms: D000328:Adult; D000368:Aged; D000469:Alkaline Phosphatase / Q000276:immunology*; D001491:Basophils / Q000166:cytology / Q000276:immunology; D015415:Biomarkers; D002097:C-Reactive Protein / Q000276:immunology*; D003371:Cough / Q000097:blood / Q000276:immunology*; D003430:Cross-Sectional Studies; D004804:Eosinophils / Q000166:cytology / Q000276:immunology; D005260:Female; D006801:Humans; D007249:Inflammation; D007958:Leukocyte Count; D007962:Leukocytes / Q000166:cytology / Q000276:immunology*; D018655:Lymphocyte Count; D008297:Male; D008875:Middle Aged; D009000:Monocytes / Q000166:cytology / Q000276:immunology; D009504:Neutrophils / Q000166:cytology / Q000276:immunology; D009749:Nutrition Surveys; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000276:immunology*; D012135:Respiratory Sounds / Q000276:immunology*; D012907:Smoking; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014807:Vitamin D; D002097:C-Reactive Protein; C104450:25-hydroxyvitamin D; D000469:Alkaline Phosphatase
keywords: COPD; NHANES; Vitamin D; inflammation; lung disease