Ever-smokers in Norway and lung cancer: median time from self-reported smoking debut to lung cancer diagnosis in 11 prospective population studies (CONOR)

Background Tobacco smoking patterns and lung cancer incidence are closely related, but with years of lag. Most smokers start smoking as teenagers, and lung cancer is diagnosed at a median age of 70 years. However, the median lag time between smoking consumption and lung cancer incidence and smoking-related mortality is commonly reported to be up to 40 years. Here we investigate the median lag time from smoking debut to lung cancer diagnosis in Norway. Methods We used the Cohort of Norway (CONOR), consisting of linked data from 11 Norwegian prospective population-based cohorts (n=180 534). The study included 80 761 ever-smokers, where 1336 developed lung cancer. Median follow-up time from inclusion in the CONOR study was 11.9 years (0.0–20.8 years) and follow-up from self-reported smoking debut was 44.2 years (2.7–85.4 years). The time from smoking initiation to lung cancer diagnosis was calculated for all cases. Results The median age of lung cancer diagnosis is 72.5 years. The mean and median time from smoking debut to lung cancer diagnosis are 51.9 (30.2–69.1) and 53.3 years, respectively. The median time from smoking debut until lung cancer diagnosis is >40 years (pversus 55.5 years and 50.7 versus 54.2 years, respectively (p Conclusion The latency between smoking debut and lung cancer diagnosis in Norwegian ever-smokers is much longer than what has previously been reported. Women and current smokers have a shorter time to diagnosis than men and former smokers, respectively. This is important knowledge in the planning of future healthcare, lung cancer screening, and prevention measures.