Efficacy of a smoking cessation program in a population of adolescent smokers in vocational schools: a public health evaluative controlled study

Inclusion criteria

All students, male and female, 15 to 20 years old inclusively, who were registered in the participating VTCs for a two-year training course were included in the sample pool. Information session on tobacco consumption was delivered to all participants regardless of smoking status. Excluded from participation were students who had current serious psychiatric disorders or who were at risk of psychological problems on quitting smoking (major depression) or who were already involved in an ongoing attempt to quit with medical monitoring.

Ethical approval for the trial was received from INSERM (the National Health and Medical Research Institute in France). The protocol was submitted to the appropriate national scientific and ethical bodies (CCTIRS and CNIL), who gave their approval. Written consent was obtained from the participants in the enhanced program, after they were given information about the study. For volunteers under 18 years old, consent also had to be obtained from their legal representatives (parents or guardian), with the result that some (n = 18) decided not to participate because they did not want to engage in a discussion with their parents.

Monitoring data for all students

The program was implemented over two inclusion periods: the first beginning in February 2008, and the second in November 2008. In both cases, data collection began with a first visit, conducted within the same period for both intervention and control schools, during which all students completed an initial assessment questionnaire asking about smoking status, sociodemographic data, knowledge, attitudes and behaviour. A final questionnaire to evaluate smoking status was administered at 12 months and contained the items in the initial questionnaire plus items to assess changes in perception of health risks associated with smoking. The final questionnaire also included items to measure changes over time in tobacco consumption among smokers. Thus, it enabled an overall assessment of the efficacy of the intervention among the target population. Clinical research assistants distributed and collected the questionnaires.

The primary outcome was 30-day point prevalence abstinence at 12 months. The rate of abstinence was defined by the number of baseline smokers who had quit at 12 months relative to the total number of baseline smokers. Baseline smokers were defined as respondents who reported that they smoked at the time of the initial questionnaire (on the question: “Are you a smoker or non-smoker?”). Abstinence was defined as being a non-smoker (i.e., ex-smoker) at 12 months and having not smoked for at least one month before that point (data from two questions in the final survey: “Are you a smoker, non-smoker, or ex-smoker?” and “How long have you not been smoking?”). The validity of responses regarding smoking status in the questionnaire was ensured by measuring expired carbon monoxide concentrations in 140 students selected at random (the calculated sample size was 130, for 90% sensitivity, 5% precision and 5% alpha). Among the 69 smokers detected by analysis of expired carbon monoxide, 68 had identified themselves as smokers, yielding a questionnaire sensitivity of 98.5% (95% CI = 96.5–100).

The secondary outcome was overall prevalence of tobacco use at 12 months.

Monitoring data for smokers who volunteered for the enhanced program

The tobacco addiction specialists used an initial questionnaire to assess the EP participants’ tobacco consumption in depth. Their tobacco consumption was subsequently monitored over time by another questionnaire completed at each of the four individual counselling sessions.

Design

This was a controlled study with a prospective longitudinal design. Thus, the smoking cessation rate in the control group was also measured, and the increase in smoking cessation in the intervention group could not be attributed to social, environmental or contextual factors such as a smoking ban. From a methodological standpoint, the observed group effect justifies our ascribing the intervention to a group rather than to an individual. From a public health perspective, it makes sense to measure the primary assessment criteria in all smokers, whether or not they participated in the enhanced program, because the school collectivity is the unit of the preventive action. We used a quasi-experimental design rather than a randomized approach, for a practical reason: the number of participating institutions was limited (n = 8) and they were strongly dissimilar in terms of training courses and size, such that randomization would probably have been ineffective [26]. Even so, despite the absence of randomization, the control and intervention groups were similar in terms of motivation, attempts and intention to quit smoking. The major differences were higher cannabis consumption in the control group (62.2% vs. 54.3%, p = 0.02) and higher dependence in the intervention group (6.4 vs. 5.9, p = 0.01). Since both characteristics are major factors of dependence, they were considered as adjustment factors.

Primary outcome

Most adolescent smokers who try to quit relapse within a year [27]. Hence, a 12-month follow-up is appropriate to evaluate the efficacy of the TABADO program [28].

Smoking status was evaluated by self-administered questionnaires and therefore was a self-reported statement of smoking. However, smoking status was confirmed in 140 randomly selected students by an exhaled carbon monoxide test. The questionnaire’s sensitivity was 98.5%, which demonstrated that smokers responded honestly to the question concerning their smoking status.

Secondary outcome

Smoking prevalence increased similarly in the two groups (+1% in the intervention group vs. +2.1% in the control group; p = 0.75). The sample size had not been calculated to assess differences in prevalences of smoking initiation.

The spontaneous abstinence rate in the general population of adolescents was previously estimated in the literature at about 5% [15]; it reached up to 7.4% in this study’s control group. This higher rate may be explained by the influence of the smoking ban in public places initiated in 2008 in France and implemented during the study period [29, 30].

Loss to follow-up

Of the 1,814 students included in the study, 1,206 (66.5%) were followed over 12 months. Unlike adolescents enrolled in the normal school system, students attending VTCs are constantly on the move, and the number of broken vocational training contracts is high (26%) [31] which accounts for the large proportion of students lost to follow-up (33.5%). That students were not followed over 12 months did not indicate their desire to exit the study, but was rather a consequence of natural fluctuations in this population. In considering this high proportion of students lost to follow-up as still being smokers, our analysis was built upon the most adverse conditions. Yet even with a hypothesis of maximum bias—that is, even assuming all smokers lost to follow-up remained smokers—the program’s efficacy remains significant (OR 1.8; 95% CI = 1.05–3.0).