Effectiveness of Negotiating Self-determination to Reduce Cigarette Consumption

This study aims to test the effectiveness of negotiating self-determination to reduce cigarette consumption (NSD-RCC) among smokers attending outpatient clinics.

Intervention Group (QP) Subjects in this group will receive a brief intervention on smoking reduction with a warning message plus a smoking reduction leaflet (the content will include a roadmap of smoking reduction strategy and information on how to cope with nicotine withdrawal symptoms). The whole intervention will last about 1 minute or slightly longer if necessary. In addition, subjects will be asked to think about a tailored smoking reduction schedule for themselves after the negotiation with the trained counsellor. For the subsequent telephone follow up in the intervention group, information on reduction and cessation will be collected, followed by a "booster" intervention, which will repeat the health warning to positively encourage them to reinforce their efforts and the next reduction target.

Control Group (QI) Subjects in the QI group will always be advised to quit immediately rather than to quit progressively. Subjects will receive a brief advice on quitting with a warning message similar to subjects in the QP group. In addition, subjects will receive a self-help quitting pamphlet published by the Hong Kong Council on Smoking and Health (COSH). Unlike the QP group, subjects in the QI group will not receive smoking reduction intervention and leaflet, and "booster" intervention during telephone follow-ups. However, they will undergo a similar schedule of telephone follow-up as those in the QP group.

Data collection

After completing the baseline questionnaire, subjects will receive proposed intervention according to their group assignment. Four consecutive follow-ups (at 1, 3, 6 and 12 months) will be conducted over the telephone by trained interviewers. Interviewers will first carry out outcome assessments with blinding to group status. Then, the group status will be disclosed so that the intervention group will receive the booster intervention and the control group will not. Smokers who have successfully quit smoking at 6-month will be invited to come back to the out-patient clinic and have biochemical validation tests (saliva cotinine test and exhaled CO test).

Analysis Data analysis will be performed using the Statistical Package for Social Science. We will compare the baseline characteristics of the participants by chi-square test for categorical variables and F-test for continuous variables between the intervention and the control group. We shall use the chi-square test to assess the effect of intervention and calculate the crude odds ratio (OR) with 95% confidence interval (CI) for the primary and secondary outcomes. Those who are lost to follow-up or refuse to participate in the validation tests, will be treated as smokers with no reduction in cigarette consumption compared with (a) baseline, as the main analysis (by intention to treat), (b) the most recent level and (c) complete case (per protocol) analysis by excluding subjects with missing data as a sensitivity analysis.