Comparison of smoking behavior change for SI and UC study groups. MRFIT Research Group

BACKGROUND. The results of MRFIT smoking intervention program are presented for the 4,103 special intervention and 4,091 usual care men who reported smoking cigarettes at the first screening visit. RESULTS. Among the special intervention men, the reported cessation rate increased from 43.1% at 12 months to 48.9% at 72 months. The reported cessation rate among the usual care men increased from 13.5% at 12 months to 28.8% at 72 months. Among smokers who reported cessation at 72 months, 51.3% of special intervention men and 22.7% of usual care men had quit smoking within the first year and remained abstinent thereafter. Average thiocyanate and expired-air carbon monoxide served as objective measures of smoking and were significantly lower among the special intervention men than among the usual care men over the entire follow-up period. The reported cessation rates at 72 months varied according to initial levels of smoking. Smokers reporting 1-19 cigarettes per day at entry were more likely to quit than heavier smokers. For each category of smoking at entry (1-19, 20-39, and 40 or more cigarettes per day) significantly more special intervention than usual care smokers reported cessation. CONCLUSION. These results indicate that the MRFIT smoking intervention program was successful in promoting early cigarette smoking cessation and maintaining cessation over the entire trial for a large percentage of cigarette smokers

Lung cancer mortality after 16 years in MRFIT participants in intervention and usual-care groups. Multiple Risk Factor Intervention Trial

PURPOSE: The Multiple Risk Factor Intervention Trial (MRFIT), a randomized clinical trial for the primary prevention of coronary heart disease, enrolled 12,866 men (including 8194 cigarette smokers) aged 35-57 years at 22 clinical centers across the United States. Participants were randomized either to special intervention (SI), which included an intensive smoking cessation program, or to usual care (UC). After 16 years of follow-up, lung cancer mortality rates were higher in the SI than in the UC group. Since rates of smoking cessation in SI were higher than those for UC for the 6 years of the trial, and since risk of lung cancer mortality is known to decline with smoking cessation, these results were unexpected. The purpose of the present study was to investigate hypotheses that could explain the higher observed lung cancer mortality rates in the SI as compared with the UC group. METHODS: Analytic methods were employed to determine whether SI and UC participants differed either in baseline characteristics or in characteristics that changed during the trial and to determine whether these differences could explain the higher rates of lung cancer mortality among SI as compared to UC participants. Rates of mortality from coronary heart (CHD) were examined to explore the possibility that prevention of CHD death may have contributed to greater mortality due to lung cancer in the SI group. RESULTS: From randomization through December 1990, 135 SI and 117 UC participants died from lung cancer. The relative difference between the SI and U groups adjusted for age and number of cigarettes smoked per day, was 1.17 (95% CI:0.92-1.51). The greatest difference between the SI and UC groups in lung cancer mortality rates occurred among the heaviest smokers at baseline who did not achieve sustained smoking cessation by year 2. In this group the rates of death from CHD were approximately the same among the SI and UC subjects. No differences in baseline characteristics were found between SI and UC smokers who did not achieve sustained cessation by year 2, and there were no differences in follow-up characteristics between the two study groups that could explain the difference in lung cancer mortality. CONCLUSIONS: None of the hypotheses proposed to explain the unexpected higher rates of lung cancer mortality among SI as compared with UC subjects were sustained by the data. Thus we conclude that the difference observed is due to chance, and that a longer period of sustained smoking cessation plus follow-up is necessary to detect a reduction in lung cancer mortality as a result of smoking cessation intervention in a randomized clinical trial