Community Intervention Trial for Smoking Cessation (COMMIT): I. cohort results from a four-year community intervention.

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Abstract
The primary hypothesis of COMMIT (Community Intervention Trial for Smoking Cessation) was that a community-level, multi-channel, 4-year intervention would increase quit rates among cigarette smokers, with heavy smokers (> or = 25 cigarettes per day) of priority. One community within each of 11 matched community pairs (10 in the United States, 1 in Canada) was randomly assigned to intervention. Endpoint cohorts totaling 10,019 heavy smokers and 10,328 light-to-moderate smokers were followed by telephone. The mean heavy smoker quit rate (i.e., the fraction of cohort members who had achieved and maintained cessation at the end of the trial) was 0.180 for intervention communities versus 0.187 for comparison communities, a nonsignificant difference (one-sided P = .68 by permutation test; 90% test-based confidence interval (CI) for the difference = -0.031, 0.019). For light-to-moderate smokers, corresponding quit rates were 0.306 and 0.275; this difference was significant (P = .004; 90% CI = 0.014, 0.047). Smokers in intervention communities had greater perceived exposure to smoking control activities, which correlated with outcome only for light-to-moderate smokers. The impact of this community-based intervention on light-to-moderate smokers, although modest, has public health importance. This intervention did not increase quit rates of heavy smokers; reaching them may require new clinical programs and policy changes.