Long-Term and Heavy Smoking as a Risk Factor for Lumbar Spinal Stenosis: Evidence from a Large-Scale, Nationwide Population-Based Cohort

<b>Background and Objectives:</b> Lumbar spinal stenosis (LSS) is a leading cause of disability in older adults, but the role of cigarette smoking in its development remains unclear. This study aimed to clarify the association between smoking and the incidence of LSS, with a focus on dose-response relationships and subgroup variations by age and sex. <b>Methods:</b> We conducted a nationwide, population-based cohort study using the Korean National Health Insurance Service database. A total of 2,123,268 adults aged ≥ 40 years who underwent health screening in 2009 were followed until LSS diagnosis, death, or 2020. Smoking status, duration, daily consumption, and pack-years were assessed. Cox proportional hazards models with progressive adjustment for demographic, lifestyle, and clinical factors were applied. <b>Results:</b> Over a mean follow-up of 8.2 years (17.5 million person-years), 721,909 new cases of LSS were identified. Fully adjusted models showed higher risk in former (HR 1.047; 95% CI, 1.039-1.056) and current smokers (HR 1.052; 95% CI, 1.044-1.060) compared with never smokers. A clear dose-response pattern was observed, with the greatest risk in heavy smokers (≥40 pack-years; HR 1.207; 95% CI, 1.191-1.222). Subgroup analyses indicated stronger associations among adults aged ≥ 65 years and in women. <b>Conclusions:</b> Cigarette smoking was independently associated with an increased risk of LSS, with risk increasing according to lifetime exposure. The findings underscore the importance of smoking cessation strategies to reduce the burden of spinal degeneration, especially in older adults and women.