The overall objective is to investigate whether or not selenium or selenium plus vitamin E prevent pulmonary function decrease.
1.1 Primary Objectives
To test longitudinally, whether:
a. the decrease in the forced expiratory volume in the first second FEV1 over 3 years is lower among men receiving daily supplement of 200 µg selenium compared to placebo.
b. the decrease in FEV1 over 3 years is lower among men receiving daily supplement of both 200 µg selenium and 400 mg vitamin E compared to placebo.
To test cross-sectionally, at 3 years post-randomization, whether:
c. FEV1 is higher among men receiving daily supplement of 200 µg selenium and 400 mg vitamin E compared to placebo.
d. FEV1 is higher among men receiving daily supplement of 200 µg selenium compared to placebo.
1.2 Secondary Objectives
a. To test longitudinally and cross-sectionally whether there is a difference in FEV1 in men receiving daily supplement of 400 mg vitamin E compared to placebo.
b. To test longitudinally and cross-sectionally whether there is a difference in FEV1 in men receiving the combination supplement arm relative to the individual supplement arms.
c. To evaluate the effect of supplementation with selenium and/or vitamin E in the subgroup of current smokers. This subgroup analysis will examine whether estimated treatment effects are larger among smokers compared to non-smokers.
d. To characterize the shape of the early response of FEV1 to supplement use in a subset of participants.
e. To evaluate whether the effect of supplementation with selenium and vitamin E in the subgroup of smokers is mediated by the level of oxidative stress, as indicated by urinary F2-isoprostanes.
f. To collect blood specimens to allow future investigation of additional markers of oxidative stress, including oxidized lipoproteins, to understand whether proposed mediating pathways indeed explain intervention effects.
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