A randomized controlled trial of vitamin E and selenium on rate of decline in lung function

Respiratory Research

Table 3 Model-based estimated mean annual decline in FEV ₁ (mL/year) by treatment group in the full sample, and stratified by cigarette smoking status (Additional file 1 : Tables S3 and S4 for model coefficients)

	Full sample			Stratified by smoking status*
All treatment groups:	Unadjusted	Adjusted (model-based)	P value ^a	Never smokers	Former smokers	Current smokers
All treatment groups:	Mean (SD) ^†	Mean (95% CI) ^††		Mean (95% CI) ^††	Mean (95% CI) ^††	Mean (95% CI) ^††
Placebo	−41 (74)	−39 (−46, −32)	reference	−40 (−52, −29)	−35 (−45, −25)	−51 (−67, −35)
Vitamin E	−34 (75)	−33 (−40, −26)	0.1866	−31 (−42, −20)	−36 (−46, −26)	−29 (−44, −14)
Selenium	−37 (74)	−38 (−44, −31)	0.7502	−37 (−48, −26)	−38 (−48, −28)	−38 (−54, −23)
Vitamin E and Selenium	−34 (74)	−34 (−41, −28)	0.3133	−32 (−44, −20)	−32 (−41, −22)	−44 (−59, −29)
Marginal Models ^b :
Any Selenium versus Placebo	Placebo	−39 (−46, −32)	reference	−40 (−52, −29)	−35 (−45, −25)	−49 (−66, −33)
Any Selenium versus Placebo	Any Selenium	−36 (−41, −31)	0.4442	−35 (−43, −27)	−35 (−42, −28)	−42 (−52, −31)
Any Vitamin E versus Placebo	Placebo	−39 (−42, −36)	reference	−40 (−51, −29)	−34 (−44, −24)	−49 (−66, −33)
Any Vitamin E versus Placebo	Any Vitamin E	−34 (−38, −30)	0.1772	−31 (−40, −23)	−34 (−41, −27)	−37 (−47, −26)

Abbreviations: FEV ₁ forced expiratory volume in the first second, mL milliliter.
*All smoking-stratified treatment vs. placebo comparisons exceeded the P value threshold of 0.05 (all values ≥ 0.25); in current smokers vitamin E vs. placebo P = 0.3552, selenium vs. placebo P = 0.4985, vitamin E + selenium vs. placebo P = 0.8887, any selenium vs. placebo P = 0.8705.
^†Mean decline (SD); calculated for men with ≥2 years between first and last pulmonary function tests where date of last test ≤ March 2009; calculated in 418 (placebo), 426 (vitamin E), 416 (selenium) and 417 (vitamin E + selenium) participants.
^††Model-based estimated mean decline and 95% confidence interval (Additional file 1: Tables S3 and S4 for regression model results); main effects models adjusted age, height, race, smoking status, time and tested time x treatment effect (effect of treatment on slope); smoking interaction models adjusted age, height, race, smoking status, and all two way interactions to test smoking x time x treatment interaction (effect of treatment on slope differs by smoking).
^aP value from mixed-effects linear regression model, with placebo reference group.
^bMarginal models combine treatment groups. Any selenium model compares participants on any selenium (selenium alone and in combination with E) to placebo. In a separate model, participants on any vitamin E (vitamin E alone and in combination with selenium) are compared to placebo.

ISSN: 1465-993X