Patterns of birth cohort-specific smoking histories in Japan, 1910-2050: a shift towards younger people?

Background: To identify important parameters for targeted smoking intervention strategies, we examined smoking initiation, cessation, and prevalence in the Japanese population by birth cohorts from 1910 to 1990.

Methods: We collected data from 34 consecutive National Health and Nutrition Surveys from 1986 to 2019 to gain nationally representative information on age at initiation, cessation and smoking intensity. Applying age-period-cohort models, we estimated annual probabilities for smoking initiation and cessation, the prevalence of people who currently smoke, and average cigarettes smoked per day (CPD), focusing on cohorts from 1910 to 1990. Under a status quo scenario, we projected these trends forward through 2050.

Results: Smoking initiation rates peaked in the late teens, with more recent cohorts peaking at younger ages in both genders. Smoking cessation rates were higher in males with notable increases after age 50, while female rates rose more gradually by age. Smoking intensity patterns were higher in males; however, recent cohorts reveal declined CPD levels with narrowing gaps between genders. Male smoking prevalence declined from 55% in 1985 to a projected 20% in 2030, while female prevalence peaked at 10% in 2005 before dropping to 8% by 2030.

Conclusions: This study highlights key patterns in smoking prevalence, initiation, cessation and intensity in Japan. The persistently higher prevalence in men, slower cessation and reductions in women, and earlier initiation in younger cohorts underscore significant gender and cohort differences. Targeted, gender-specific interventions, early prevention and sustained efforts to address health disparities are crucial to tackling the unique challenges faced by Japanese populations.