Global, regional, and national burden of low-back pain attributable to smoking from 1990 to 2021: An age-period-cohort and joinpoint analysis of the Global Burden of Disease Study 2021
INTRODUCTION Low-back pain (LBP) is the leading cause of disability worldwide. Although smoking is a well-established, modifiable risk factor that accelerates intervertebral disc degeneration, comprehensive spatiotemporal analyses of its attributable burden remain scarce. This study assessed the global burden of smoking-attributable LBP from 1990 to 2021, elucidating the underlying temporal dynamics and socioeconomic inequalities. METHODS Data were extracted from the Global Burden of Disease (GBD) study 2021. We evaluated absolute disability-adjusted life years (DALYs), age-standardized DALYs rate (ASDR), and estimated annual percentage change (EAPC) across 204 countries and territories. To disentangle temporal trends, age-period-cohort and joinpoint regression models were applied. The spatial-temporal relationship between the burden and the sociodemographic index (SDI) was also examined. RESULTS Globally, the absolute number of DALYs for smoking-attributable LBP increased by 29.6% to 8.67 million in 2021, primarily driven by population growth and aging. Conversely, the global ASDR decreased significantly by 35.8% to 99.95. Males bore a substantially higher burden than females, with biological risk peaking at 60–69 years (inverted U-shape). The ASDR trajectory exhibited a distinct inverted U-shaped relationship with SDI; while high-income nations experienced rapid declines (e.g. Denmark, EAPC= -2.29), the burden surged in specific developing regions (e.g. Afghanistan, EAPC=2.37). Joinpoint analysis revealed an accelerated global decline from 2016 to 2021 (annual percent change, APC= -1.70). Age-period-cohort modeling confirmed continuous monotonic reductions in both period and cohort relative risks, highlighting a profound ‘generational dividend’. CONCLUSIONS Despite continuous improvements in age-standardized rates driven by recent global tobacco control policies and younger birth cohorts, the absolute burden of smoking-attributable LBP continues to grow. Progress is alarmingly unequal, heavily favoring high-income countries while intensifying in developing nations. Global health strategies must prioritize equitable implementation of tobacco control in lower income regions and integrate cessation programs into occupational health initiatives and strengthening of targeted tobacco control policies, particularly in low- and middle-income regions.