Vitamin E and beta-carotene supplementation and hospital-treated pneumonia incidence in male smokers.

BACKGROUND

Vitamin E and beta-carotene affect various measures of immune function and accordingly might influence the predisposition of humans to infections. However, only few controlled trials have tested this hypothesis.

STUDY OBJECTIVE

To examine whether vitamin E or beta-carotene supplementation affects the risk of pneumonia in a controlled trial.

DESIGN AND SETTING

The Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) study, a randomized, double-blind, placebo-controlled trial that examined the effects of vitamin E, 50 mg/d, and beta-carotene, 20 mg/d, on lung cancer using a 2 x 2 factorial design. The trial was conducted in the general community in southwestern Finland in 1985 to 1993; the intervention lasted for 6.1 years (median). The hypothesis being tested in the present study was formulated after the trial was closed.

PARTICIPANTS

ATBC study cohort of 29,133 men aged 50 to 69 years, who smoked at least five cigarettes per day, at baseline.

MAIN OUTCOME MEASURE

The first occurrence of hospital-treated pneumonia was retrieved from the national hospital discharge register (898 cases).

RESULTS

Vitamin E supplementation had no overall effect on the incidence of pneumonia (relative risk [RR], 1.00; 95% confidence interval [CI], 0.88 to 1.14) nor had beta-carotene supplementation (RR, 0.98; 95% CI, 0.85 to 1.11). Nevertheless, the age of smoking initiation was a highly significant modifying factor. Among subjects who had initiated smoking at a later age (> or =21 years; n = 7,469 with 196 pneumonia cases), vitamin E supplementation decreased the risk of pneumonia (RR, 0.65; 95% CI, 0.49 to 0.86), whereas beta-carotene supplementation increased the risk (RR, 1.42; 95% CI, 1.07 to 1.89).

CONCLUSIONS

Data from this large controlled trial suggest that vitamin E and beta-carotene supplementation have no overall effect on the risk of hospital-treated pneumonia in older male smokers, but our subgroup finding that vitamin E seemed to benefit subjects who initiated smoking at a later age warrants further investigation.