Tobacco price increase and smoking behaviour changes in various subgroups: a nationwide longitudinal 7-year follow-up study among a middle-aged Japanese population

Objective Few longitudinal studies have examined the effect of tobacco price increase on both cessation among smokers and relapse among quitters. Our objective was to investigate the differential impact of the tobacco price increase on the changes in smoking status in the total population and various subgroups. Methods We analysed data from a Japanese nationally representative longitudinal study of 30 773 individuals aged 50-59 years (weighted sum of discrete-time number = 215 411) with smoking information, using inverse probability weighting to account for non-response at follow-up. Generalised estimating equation models were used to calculate the odds ratios (ORs) for smoking behavioural changes (cessation among smokers and relapse among quitters), using discrete-time design. Stratified analyses were conducted according to demographic, socioeconomic and health behavioural characteristics. Results From 2005 to 2012, current smoker prevalence among the middle-aged Japanese population decreased from 30.5% to 24.3%. Of all the factors surveyed, only the tobacco price increase in 2010 (up by 37%, the highest increase during the period) was significantly associated with both cessation among smokers (OR 2.14, 95% confidence interval 1.90 to 2.41) and prevention of relapse among quitters (0.60, 0.46 to 0.77). Regarding the subgroup analysis, the tobacco price increase was associated with a significant reduction in relapse in the lowest income, recent quitters and very poor health subgroups. However, different associations were observed for cessation; a significant association between price increase and cessation was observed among all subgroups except for the heavy smoker and recently unemployed subgroups. Conclusions We confirmed that the tobacco price rise was associated with increasing cessation and decreasing relapse concurrently. Furthermore, this price rise was associated with favourable smoking changes in nearly all population subgroups; a large differential impact was not observed across the various subgroups.