Smoking cessation intervention in a large randomised population-based study. The Inter99 study.

Abstract

Several large and well-conducted community interventions have failed to detect an effect on prevalence of smoking. Two thousand four hundred eight daily smokers in all motivational stages were actively recruited and included in a randomised population-based intervention study in Copenhagen, Denmark. All smokers completed a questionnaire and underwent a health examination and a lifestyle consultation. Daily smokers in the high intensity intervention group were offered assistance to quit in smoking cessation groups. The validated abstinence rate at 1-year follow-up was 16.3% in the high intensity group and 12.7% in the low intensity group compared with a self-reported abstinence rate of 7.3% in the background population. The adjusted odds ratio of abstinence in the high intervention group was significantly higher, OR = 2.2 (1.6-3.0) than in the background population, also in the 'intention-to-treat' analyses, OR = 1.5 (1.1-2.0). Higher socioeconomic status, higher age at onset of daily smoking, and a higher wish to quit were predictors of success. In a population-based setting, using active recruitment and offering assistance to quit, it was possible to include many smokers and to achieve a significantly higher validated abstinence in the high intensity intervention than in the background population, even when using 'intention-to-treat' analyses.