Classification of trends in male smoking rate by prefecture in Japan

Abstract

Objective: Smoking rate varies across Japanese prefectures. However, it isn’t clear whether there are differences in trends in smoking rate by prefecture. In this study, we estimated the trend in smoking rate by prefecture and categorized by feature. Methods: Male smoking rates by prefecture from 2001 through 2016 were obtained from dataset which is provided by Cancer Registry and Statistics, Cancer Information Service, National Cancer Center, Japan. Joinpoint analysis was used to compute annual percentage changes (APC) in male smoking rate by prefecture. And we categorized based on whether the prefecture had a joinpoint and how large the APC was. Results and Conclusions: We showed that three prefectures had a joinpoint. Specifically, Saitama, Chiba and Nara prefectures. In all those prefectures, the point was observed at 2010. And smoking rates showed a significant decrease until 2010, while trends were flat thereafter. Although the other 44 prefectures had no joinpoint, those prefectures’ APCs showed wide ranges (Min: -10.77, Max: -5.21). In 2010, tax rate of tobacco was increased. That is, after tax increase of tobacco, there were differences about decrease of smoking rate between prefectures with and without a joinpoint. Furthermore, there were differences in the slope of decrease even across the prefectures without a joinpoint. We need to examine reasons of those differences considering the situation of prefectural tobacco control policy.