Age- and sex-specific smoking trends by birth cohort in Norway, 1978–2024: an analysis of cross-sectional survey data

Background Smoking is the primary cause of lung cancer, the leading cause of cancer-related mortality in Norway. To inform disease modeling and tobacco control policies, including lung cancer screening, we estimated sex-specific, birth-cohort smoking behaviors among Norwegians born between 1950 and 2000 using national survey data. Methods We analyzed nationally representative cross-sectional survey data from 1978 to 2024 (n = 78,282) to reconstruct smoking trends and smoking intensity in Norway. We used a previously established Age–Period–Cohort modeling framework to estimate cohort-specific prevalence of daily ever-smoking, probabilities of smoking initiation and cessation, prevalence of daily current-smoking, and average cigarettes smoked per day (CPD). Analyses were conducted separately by sex assigned at birth for cohorts born between 1950 and 2000. Findings Daily ever-smoking prevalence peaked in the 1950 birth cohort, reaching 70% (90% CI 66%–91%) among males and 66% (90% CI 55%–89%) among females, alongside similar peaks in smoking initiation probabilities, 13% (90% CI 12%–24%) for males and 12% (90% CI 10%–23%) for females. Smoking cessation probabilities increased with age within each birth cohort, rising from approximately 0% to 5% over 40 years in earlier cohorts, compared with an increase from about 5% to 15% over 20 years from the 1965 birth cohort onward. Smoking intensity peaked at 15 CPD among males and 12 CPD among females. Although smoking intensity declined in both sexes after the 1975 birth cohort, it remained higher among males, with peak model-estimated CPD decreasing from approximately 13.5 to 10 cigarettes in males and from 11.5 to 7.5 cigarettes in females between the 1980 and 2000 birth cohorts. Interpretation Smoking behavior in Norway has changed across generations, with declining smoking initiation rates, increased smoking cessation, and lower cigarettes per day. Understanding these trends provides essential inputs to inform tobacco control and lung cancer prevention policies in Norway. Funding Norwegian Cancer Society, National Cancer Institute of the National Institutes of Health, U.S. Food and Drug Administration.