摘要：Backgrounds: Smoking in childhood has become an important public health concern. Previous studies have reported on secular trends in childhood smoking rates and compared with smoking rates at fixed ages. They also described secular trends regarding the prevalence of smoking at fixed ages. The variations in smoking rate of young children and adolescents by follow-up groups have not been studied by follow-up groups at a national level. Objective: We looked at trends and generational impacts on smoking rate by using follow-up groups of male Japanese high school students to quantitatively assess differences in trends, based on multiple nationwide data from the Japanese Youth Tobacco and Drinking Surveys gathered every 4 years between 1996 and 2008. Methods: The surveys were nationwide, cross-sectional random sampling surveys given every 4 years from 1996 to 2008, using the single-stage cluster sampling methodology. The cluster unit of the sampling was school. The survey targeted junior and senior high school students from schools selected through Japan using the National School Directory. Students enrolled in the sampled schools were subjects of the study. Participants were 53,925 high school students from 7th grade to 11th grade in 1996, 2000, 2004 and 2008. We divided the three follow-up groups every 4 years from 1996 to 2004 for male junior high school students in 7th grades, age 13. The end periods were 4 years later when they had become 11th graders, age 17, from 2000 to 2008. Main outcome measures in this study were life time smoking, current smoking within 30 days and daily smoking at 7th or 11th grade and the trend of the smoking rates between 7th to 11th grades. Results: Life time smoking rate, current smoking rate and daily smoking rate in Japanese high school students decreased at 7th grade from 1996 to 2004. They also decreased at 11th grade from 2000 to 2008. However, the slopes differed among their follow-up groups. The increments in their smoking rates from 7th grade to 11th grade in male high school students were smaller in recent follow-up groups both in 2000 and in 2004 than in follow-up groups in 1996. Then, those increments in follow-up groups between in 2000 and in 2004 were similar in lifetime smoking rate and current smoking rate. Conclusions: We have shown that monitoring trends by follow-up group are important in studying smoking for public health. Values of smoking rates from a young age to adolescence by follow-up group should be examined. Values of smoking rate and regular changes in smoking rate are important because smoking rate changes dynamically during adolescence. Not only trends in smoking rates at fixed ages, but also generational impacts should be considered by using follow-up groups to study smoking behaviors among students. We need to continue careful monitoring of follow-up group smoking prevalence. When long-term health promotions are planned or assessed, policy makers need to look at changes in follow-up groups.
关键词：Smoking Rates; Repeated Cross-Sectional Study; Nationwide Survey; Japan
