This controlled, prospective, quasi-experimental study compared two groups. The intervention group underwent the TABADO program, and the control group, drawn from the same training curriculum but from different VTCs, received no specific intervention other than the educational services usually available.
Setting and participants
The sampling pool for the intervention and control groups included all students attending a participating VTC in the Lorraine region (eastern France, 2.3 million inhabitants, 51 VTCs, 16,500 trainees) during the school years 2007–2008 and 2008–2009. For logistical reasons, we included only classes of more than 10 pupils whose training schedule (i.e., one week of VTC courses alternating with three weeks at their employer’s facility) was similar.
All VTCs in Lorraine (n = 51) were invited to participate. Among them, eight agreed to be included in the study and to be designated indiscriminately as either an intervention or a control school. Because of the limited number of centres and their strong dissimilarities in terms of training courses and size (from 30 to 300 apprentices), we used pragmatic sampling rather than randomization to allocate the centres (each was assigned to either the intervention or control group at the time of its inclusion with a view to ensuring students’ areas of study were balanced between both groups).
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.
The TABADO intervention combined a general program aimed at all participants, in the form of an information session on tobacco consumption, with a specific enhanced program undertaken by some smokers on a volunteer basis (identified here as “EP participants”) . This volunteer contingent underwent two stages: 1) individual consultation with a team of physicians specialized in tobacco addiction who visited the VTC and provided personalized assistance with choosing nicotine replacement therapy (patches or gums), if needed; and 2) a small group approach, supervised by the same physicians, consisting of discussion sessions to share experiences, strengthen motivation and prevent relapse. Each group underwent four sessions spread over three months (to accommodate the 1:3 week training schedule described above); preceding those group sessions, individual counselling was also offered to each student. In cases where nicotine replacement treatment was contraindicated (hypersensitivity to one of the components, occasional smoking, or skin infection that might interfere with the patch, if used), only the four cognitive-behavioural group sessions preceded by individual counselling were provided.
Sample size calculation
Based on the literature, we expected a maximum 5% spontaneous quit rate . We hypothesized this rate would double in the intervention group’s EP participants after one year. This 10% rate was based on the assumption of an effective participation of 50% of smokers in the intervention group, with a smoking cessation rate of 15%, and the regular 5% for non-EP participants in the intervention group. With two groups of the same size, a two-sided α risk of 5% and a power of 85%, 500 smokers per group were needed. Thus, the total number of students to be included was 2000 (anticipating a smoking prevalence of 50%).
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.
30-day point prevalence abstinence at 12 months was compared by multivariate logistic regression adjusting for predefined characteristics (age, sex, and training course), differing characteristics between the two groups at baseline (i.e., cannabis consumption, Hooked On Nicotine Checklist [HONC] score) and tobacco consumption.
The analysis of VTC effect by estimating the intraclass correlation coefficient(ICC) led us to decide to choose a classical model rather than a hierarchical model (intraclass correlation coefficient = 0.04). The analysis was based on intention to treat. Loss to follow-up was considered in a first analysis as non-abstinence and in a second analysis as missing data. Comparisons between two categorical variables were done by chi-square test and between two continuous variables by Student’s t test. A p-value of <0.05 was considered statistically significant. Analyses used SAS 9.2 (SAS Institute, Cary, NC).