Hierarchical Age-Period-Cohort Analysis of Smoking Prevalence and Cigarettes Per Day in South Korea

Abstract Introduction Since the early 2000s, South Korea has implemented tobacco control policies; however, smoking behaviors have not been sufficiently evaluated through age-period-cohort (APC) analysis. Methods A hierarchical APC model was applied to two nationwide surveys, including socioeconomic and lifestyle factors. Age was defined at participation, period as survey year, and cohort as birth year. Current smoking prevalence was analyzed among 54,917 men and 69,551 women aged 12–80 years from the Korea National Health and Nutrition Examination Survey I–VIII (1998, 2001, 2005, and 2007–2023). Cigarettes per day (CPD) were assessed among 518,786 male and 44,410 female smokers aged 19–80 from the Korea Community Health Survey 2008–2022. Results Smoking prevalence declined after the age of the early 20s and early 40s among men and women, respectively. Among men, the cohort effect on smoking prevalence stagnated starting with the 1980s birth cohort, whereas in women, a decline was observed from the 1990s birth cohort onward. Disparities in smoking widened, particularly among individuals with lower education levels or current drinkers (P for interaction 0.001). CPD exhibited an inverted U-shape, peaking in the late 40s, with minimal variation (1 CPD) among women. After the coronavirus disease 2019 pandemic, CPD increased only among women (P 0.001), while cohort effects on CPD were not significant. Conclusions The decline in smoking prevalence stagnated, with widening disparities by educational attainment, marital status, and alcohol consumption. Policies should address these disparities and include sex-specific strategies to accelerate smoking reduction. Implications This study highlights the stagnation in the decline of smoking prevalence in South Korea, particularly among recent birth cohorts with lower educational attainment and current alcohol consumption. Notably, an increase in cigarette consumption following the COVID-19 pandemic was observed only among women. These findings underscore the importance of implementing gender-responsive and equity-oriented tobacco control policies that address behavioral and socioeconomic disparities to sustain progress in smoking reduction.