Serum vitamin C levels and use of health care resources for wheezing episodes

Background: Evidence suggests that the antioxidant vitamin C may play a rol e in lung function and wheezing, although the data are limited to laborator y evaluation of pulmonary function. Objective: To examine the relationship among serum vitamin C levels, wheezi ng episodes, and use of health care services. Methods: Analysis of adult subjects (aged greater than or equal to 17 years ) surveyed in the third National Health and Nutrition Examination Survey (1 988-1994) (n = 19 760), including measurements of serum vitamin C levels an d self-reports of wheezing episodes, ambulatory health care visits, and ove rnight hospitalizations for wheezing. Results: A large proportion of individuals (2377/19 760 [12.0%]) have recei ved a diagnosis of asthma, chronic bronchitis, or emphysema. Among 874 indi viduals having an ambulatory visit for wheezing, 408 (46.7%) did not have a diagnosed respiratory condition. Similarly, among 159 individuals hospital ized for wheezing, 61 (38.4%) did not have a diagnosed respiratory conditio n. Serum vitamin C level had no significant relationship with reported diag nosis of respiratory conditions, episodes of wheezing, or use of health car e services for wheezing. In a model computed only with individuals with low or high serum vitamin C levels, after adjustment for potential confounders , no statistically significant relationship was found between serum vitamin C levels and ambulatory care (odds ratio, 0.78; 95% confidence interval, 0 .58-1.05) or hospitalization for wheezing episodes (odds ratio, 1.21; 95% c onfidence interval, 0.67-2.21). Conclusions: Serum vitamin C levels do not appear to be a marker for use of health care services for wheezing. Future investigations of the role of an tioxidants in managing respiratory conditions should focus on the clinicall y important outcomes of health care use.