Smoking prevalence among adults in China Mainland and their age of smoking initiation during adolescence: a national cross-sectional study

Objectives This study aims to calculate the national prevalence of smoking among Chinese adults and to describe the hazard of smoking initiation by age during their adolescence, as well as the disparities in sex, residence and age groups.Design A cross-sectional study.Setting The data were derived from a multistage sampling study conducted in 120 cities in China Mainland.Participants A total of 9963 participants aged >= 19 years were included.Primary outcome measures Survival analysis was used to quantify the hazards of smoking initiation by a single year of age during adolescence, and the log-rank test was used to compare the hazard curves across subgroups.Results The prevalence of current smoking among males and females was 27.7% and 2.0%, respectively, and 56.2% of current smokers began smoking at or before the age of 18. The hazard of smoking initiation during adolescence for females was less than 0.5%, and the hazard for males increased gradually before 14 years of age and increased sharply at age 15 (4.34%), then peaked at age 18 (6.24%). Males in rural experienced a higher hazard of smoking initiation than those in urban (chi 2=5.35, p=0.02) and no such difference was found in females. By the age of 18 years, 11.7% of participants (1.8% for females and 23.4% for males) had ever smoked.Conclusions The prevalence of smoking among Chinese adults was lower than once reported. Males experienced higher hazards of smoking initiation at all ages than females. The hazard pattern suggests that the key focus for smoking prevention are males and adolescents aged 15-18 years, and future interventions should be delivered to the right target population at the appropriate time.