Background Recent studies suggest a role for vitamin D in innate immunity, including the prevention of respiratory tract infections (RTIs). We hypothesize that serum 25-hydroxyvitamin D (25[OH]D) levels are inversely associated with self-reported recent upper RTI (URTI). Methods We performed a secondary analysis of the Third National Health and Nutrition Examination Survey, a probability survey of the US population conducted between 1988 and 1994. We examined the association between 25(OH)D level and recent URTI in 18 883 participants 12 years and older. The analysis adjusted for demographics and clinical factors (season, body mass index, smoking history, asthma, and chronic obstructive pulmonary disease). Results The median serum 25(OH)D level was 29 ng/mL (to convert to nanomoles per liter, multiply by 2.496) (interquartile range, 21–37 ng/mL), and 19% (95% confidence interval [CI], 18%–20%) of participants reported a recent URTI. Recent URTI was reported by 24% of participants with 25(OH)D levels less than 10 ng/mL, by 20% with levels of 10 to less than 30 ng/mL, and by 17% with levels of 30 ng/mL or more (P<.001). Even after adjusting for demographic and clinical characteristics, lower 25(OH)D levels were independently associated with recent URTI (compared with 25[OH]D levels of ≥30 ng/mL: odds ratio [OR], 1.36; 95% CI, 1.01–1.84 for <10 ng/mL and 1.24; 1.07–1.43 for 10 to <30 ng/mL). The association between 25(OH)D level and URTI seemed to be stronger in individuals with asthma and chronic obstructive pulmonary disease (OR, 5.67 and 2.26, respectively). Conclusions Serum 25(OH)D levels are inversely associated with recent URTI. This association may be stronger in those with respiratory tract diseases. Randomized controlled trials are warranted to explore the effects of vitamin D supplementation on RTI.

OBJECTIVE: To examine temporal trend in the national incidence of bronchiolitis hospitalizations, use of mechanical ventilation, and hospital charges between 2000 and 2009. METHODS: We performed a serial, cross-sectional analysis of a nationally representative sample of children hospitalized with bronchiolitis. The Kids Inpatient Database was used to identify children &lt;2 years of age with bronchiolitis by International Classification of Diseases, Ninth Revision, Clinical Modification code 466.1. Primary outcome measures were incidence of bronchiolitis hospitalizations, mechanical ventilation (noninvasive or invasive) use, and hospital charges. Temporal trends were evaluated accounting for sampling weights. RESULTS: The 4 separated years (2000, 2003, 2006, and 2009) of national discharge data included 544 828 weighted discharges with bronchiolitis. Between 2000 and 2009, the incidence of bronchiolitis hospitalization decreased from 17.9 to 14.9 per 1000 person-years among all US children aged &lt;2 years (17% decrease; Ptrend &lt; .001). By contrast, there was an increase in children with high-risk medical conditions (5.9%–7.9%; 34% increase; Ptrend &lt; .001) and use of mechanical ventilation (1.9%–2.3%; 21% increase; Ptrend = .008). Nationwide hospital charges increased from $1.34 billion to $1.73 billion (30% increase; Ptrend &lt; .001); this increase was driven by a rise in the geometric mean of hospital charges per case from $6380 to $8530 (34% increase; Ptrend &lt; .001). CONCLUSIONS: Between 2000 and 2009, we found a significant decline in bronchiolitis hospitalizations among US children. By contrast, use of mechanical ventilation and hospital charges for bronchiolitis significantly increased over this same period.

Kids' Inpatient Databases) of children (age ,2 years) hospitalized for bronchiolitis. We identified all children hospitalized with bronchiolitis by using International Classification of Diseases, Ninth Revision, Clinical Modification 466.1 and International Classification of Diseases, 10th Revision, Clinical Modification J21. Complex chronic conditions were defined by the pediatric complex chronic conditions classification by using inpatient data. The primary outcomes were the incidence of bronchiolitis hospitalizations, mechanical ventilation use, and hospital direct cost. We examined the trends accounting for sampling weights. RESULTS: From 2000 to 2016, the incidence of bronchiolitis hospitalization decreased from 17.9 to 13.5 per 1000 person-years in US children (25% decrease; P trend , .001). In contrast, the proportion of bronchiolitis hospitalizations among overall hospitalizations increased from 16% to 18% (P trend , .001). There was an increase in the proportion of children with a complex chronic condition (6%-13%; 117% increase), hospitalization to children's hospital (15%-29%; 93% increase), and mechanical ventilation use (2%-5%; 184% increase; all P trend , .