Background Smoking is associated with poor health-related quality of life (HRQL); however, there are few data regarding effects of smoking cessation treatment on HRQL. The purpose of this study was to describe changes in HRQL after smoking cessation treatment and to elucidate factors influencing this improvement in HRQL.

Setting Smoking cessation clinic at a 358-bed community teaching hospital in Japan.

Methods We conducted a prospective cohort study of cigarette smokers who participated in a 3-month smoking cessation programme. HRQL was assessed at baseline and at the end of the programme using the St. George's Respiratory Questionnaire (SGRQ). The abstinence was subjected to verification by an exhaled CO level of ≤10 ppm.

Results Of 570 participants in the programme, 277 (mean age: 60.9±12.2 y, male/female=180/97) were eligible; excluded were 277 participants who dropped out of the programme and 16 for whom SGRQs were not available or were incomplete. Initial prescribed pharmacotherapy was transdermal nicotine patches in 160 participants and varenicline in 117. At 12 weeks, SGRQ scores improved significantly as follows (mean±SD): Δ symptoms score, −5.7±16.0; Δ activity score, −4.4±18.3; Δ impact score, −5.3±13.5 and Δ total score, −5.1±12.2 (p<0.0001 in all cases). There were no significant differences in changes in SGRQ scores between quitters (n=183) and continuous smokers (n=94). In a multivariate analysis, only the average nicotine addiction level according to the Tobacco Dependence Screener test was associated with a clinically significant improvement in the SGRQ (OR 1.35 (95% CI 1.15 to 1.59)). Marked reduction in number of cigarettes smoked with a corresponding low median exhaled CO level of 7 ppm in continuous smokers following therapy was observed.

Conclusions Smoking cessation treatment improved HRQL regardless of quit status. Baseline nicotine addiction level was predictive of that improvement.