The Respiratory Ancillary Study (RAS) to SELECT

BACKGROUND:

There is compelling evidence from observational epidemiologic studies that intakes of nutrients with antioxidant properties are associated with reduced risks of chronic obstructive disease (COPD) and increased lung function. This study is ancillary to the multisite Selenium and Vitamin E Cancer Prevention Trial (SELECT), a 4-arm placebo-controlled, double-blinded randomized trial in 35,000 men testing whether daily supplementation with vitamin E (400mg alpha-tocopherol), selenium (200 micrograms selenomethionine) or both vitamin E and selenium can prevent prostate cancer.

DESIGN NARRATIVE:

This study is ancillary to the multisite Selenium and Vitamin E Cancer Prevention Trial (SELECT), a 4-arm placebo-controlled, double-blinded randomized trial in 35,000 men testing whether daily supplementation with vitamin E (400mg alpha-tocopherol), selenium (200 micrograms selenomethionine) or both vitamin E and selenium can prevent prostate cancer. A total of 3,000 SELECT participants will be enrolled for this respiratory ancillary study, and data collection will be extended to include pulmonary function, respiratory disease, and respiratory symptoms. Biological measures of nutrient exposure (serum vitamin E and selenium) and plasma lipids (total and high-density lipoprotein cholesterol) will be collected on all participants and oxidant burden (urinary F2-isoprostane) on a sub sample of heavy smokers and men with COPD. The primary outcome will be change over about 36 months in forced expiratory volume in the first second (FEV1). FEV1 is a valid and reliable measure of respiratory function that strongly predicts COPD and mortality. Extensive data on diet and dietary supplement use are being collected by the SELECT parent study. All specific aims examine pre-specified contrasts between the 4 arms of the SELECT randomized trial. The underlying hypothesis is that supplements will reduce the age related decline in FEV1 and thus at the 3-year follow-up FEV1, which will be tested in longitudinal and cross-sectional models. A secondary aim considers whether the effect of supplementation is greater among smokers (high burden of exogenous oxidants) who, by purposive selection of the study sites, will comprise about 25% of the sample.