Background: Evidence suggests that the antioxidant vitamin C may play a role in lung function and wheezing, although the data are limited to laboratory evaluation of pulmonary function.
Objective: To examine the relationship among serum vitamin C levels, wheezing episodes, and use of health care services.
Methods: Analysis of adult subjects (aged > or = 17 years) surveyed in the third National Health and Nutrition Examination Survey (1988-1994) (n = 19,760), including measurements of serum vitamin C levels and self-reports of wheezing episodes, ambulatory health care visits, and overnight hospitalizations for wheezing.
Results: A large proportion of individuals (2377/19,760 [12.0%]) have received a diagnosis of asthma, chronic bronchitis, or emphysema. Among 874 individuals having an ambulatory visit for wheezing, 408 (46.7%) did not have a diagnosed respiratory conditions. Similarly, among 159 individuals hospitalized for wheezing, 61 (38.4%) did not have a diagnosed respiratory condition. Serum vitamin C level had no significant relationship with reported diagnosis of respiratory conditions, episodes of wheezing, or use of health care 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% confidence 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 antioxidants in managing respiratory conditions should focus on the clinically important outcomes of health care use.