The results we obtained with intensive individual and group interventions were worse than expected. We wish to highlight two possible reasons for this: the lack of a consistent definition for individuals in the preparatory phase before smoking cessation, and the scarce use of drug therapy by health professionals.
Some individuals who were presumably in the preparatory phase dropped out of the interventions after the first visit or even before. This shows hat their level of "preparedness" was low. The strategy employed to ascertain preparedness status (asking individuals if they felt prepared and able to fix a date to quit smoking) may have been a poor one; it may have been better to assess the smoker's state of preparedness in greater depth through an open interview. Nonetheless, the different stages of the process of change are known to fluctuate . In fact, authors such as Rollnick et al.  have suggested that preparedness should be viewed as a continuum along the process of smoking cessation instead of a well-defined phase. Thus, we may have incurred in selection bias by having used too simple a method to identify individuals who were prepared to quit smoking, whom we felt would be the ones to benefit the most from an intensive intervention.
An unequal number of subjects in each trial arm, together with differences among groups in subjects treatment preferences, could be another source of selection bias. The trial arms were not balanced because patients were unequally recruited among participating health centers, not because they were included only after being allocated to a trial arm that met their treatment expectations. Actually, the number of subjects who never attended an intervention visit after allocation was 4 in III, 1 in IGI and 2 in MI. The percentage of subjects who were allocated to an intervention in line with their expectations may have been due to chance.
Drugs (nicotine derivatives or bupropion) were used little during both individual and group interventions. Primary health care physicians' and nurses' perceptions of the effectiveness and safety of such treatments may be worth exploring, since according to Vogt et al., they may influence their prescription . Perhaps not enough emphasis was placed on the effectiveness and benefits of drug therapy during health workers' training. It would have been a good idea, for instance, to provide them with illustrative experiences such as that of New York, where drugs were dispensed free of charge and abstinence rates greater than 20% were attained at one year . On the other hand, the definition used for "being on drug therapy" - having been under treatment during one of the intervention visits, whether continuously or not - may explain why none of the individuals being treated with nicotine derivatives quit smoking.
We do not feel the poor results obtained are part of the described trend towards decreased effectiveness of anti-smoking treatments because non-quitters are the more recalcitrant individuals who never succeed in shaking the addiction . In our setting, the last twenty years have seen a drop in smoking prevalence, especially in males , although the prevalence rate continues to be high, particularly among the lower social classes . In the Balearic Islands in particular, 33.7% of the men and 20.3% of the women report being daily smokers .
Individual intervention yielded somewhat better results than group intervention, which is six times as long. This is precisely the disadvantage of group interventions, since a large percentage of patients drop out in the course of the sessions. As shown in this study, however, the time invested by health workers was the only factor associated with smoking cessation. Thus, adherence to treatment is crucial, as already demonstrated by other studies in which a dose-response relationship was found between the number of visits and a successful outcome . Studying why participants drop out of sessions would be useful in trying to prevent such losses and in learning to appropriately choose candidates for intensive interventions.
Based on our findings, no specific type of intervention can be recommended to help smokers who attend health centers to quit smoking. It is probably best for health centers to provide group as well as individual interventions, and minimal interventions in addition to intensive ones. On the one hand, repeated minimal intervention is very cost-effective ; on the other, group intervention requires more available resources, such as nursing staff. Individual intervention could be reserved for smokers who demand individualized care , although it is worth remembering that smokers can quit smoking on their own and that health care workers as well as public health officials should encourage them to do so and pass laws restricting the use of tobacco products in public spaces .
The study has two main limitations: non-attainment of the estimated sample size and losses to follow-up.
We were unable to attain the desired sample size because during the study more than 20% of participating doctors and nurses were transferred to other health centers. As a result, we had to identify new professionals to recruit smokers and train them in conducting smoking cessation interventions. Our study lacked sufficient power to detect statistically significant differences between the results of intensive individual and group interventions, but the findings suggest that we were wrong in our hypothesis that intensive group intervention for smoking cessation is more effective than intensive individual intervention.
When we compared self-reported point abstinence rates with continued abstinence rates confirmed with CO, we observed better results (12% for III, 10% for IGI and 6% for MI compared with 7% for III, 5% for IGI and 1% for MI). We consider self-reported point abstinence rates more realistic and similar to those obtained in previous studies. Although continuous abstinence is considered the gold standard outcome for smoking cessation , some studies have shown that smokers do not lie about their smoking status when asked about it directly .
Patient follow-up presented additional difficulties, both for patients who quit smoking and for those who did not. Participants in the first group did not understand why they had to continue visiting the health centre since they had quit smoking already; those in the second group felt embarrassed about not having been able to quit. Poor compliance with follow-up visits made us choose point self-reported smoking cessation as the outcome measure for exploring other variables potentially associated with having quit smoking.