Sargeant, Lincoln A.; Jaeckel, A. ; Wareham, N. J.
Author Affiliation, Ana.
Tropical Medicine Research Institute
Interaction of vitamin C with the relation between smoking and obstructive airways disease in EPIC Norfolk. European Prospective Investigation into Cancer and Nutrition
European Respiratory Journal
Date of Publication
Previous studies have reported an association between plasma vitamin C levels and respiratory function, but have not examined the role of vitamin C as an effect modifier of the relation between cigarette smoking and obstructive airways disease (OAD). This question was investigated in a cross-sectional analysis of a population-based study of 3,714 males and 4,256 females aged 45-74 yrs. Undiagnosed OAD was defined as a forced expiratory volume in one second (FEV1) of <80% of the predicted value and FEV1/forced vital capacity of <70% without self- reported OAD. An increase of 20 micromol x L(-1) (or 1 SD) in plasma vitamin C concentration was associated with a 13% reduction in the risk of having OAD (adjusted odds ratio (OR) (95% confidence interval) 0.87 (0.77-0.98)). The OR for current smokers relative to never smokers within the lowest quintile of plasma vitamin C concentration was 5.93 (3.03-11.61). The risk in the upper four quintiles was 2.84 (1.92- 4.19). Within the lowest quintile of plasma vitamin C concentration, the risk in former smokers was strongly related to the time since quitting (interaction significant, p=0.001). These findings support a protective role for vitamin C against the risk of obstructive airways disease and support the hypothesis that vitamin C may be an effect modifier for the adverse effects of smoking on the risk of obstructive airways disease.....