Global burden of lung cancer attributable to secondhand smoke (1990–2021) and predictive trends to 2035

Secondhand smoke (SHS) is closely related to lung cancer, however, the global burden of lung cancer caused by SHS remains unclear. This study used 2021 Global Burden of Disease data (GBD) to comprehensively assess the lung cancer burden associated with SHS. The number of deaths and disability-adjusted life years (DALYs) attributable to SHS was found to be 0.098 million and 2.4 million, respectively in 2021. Nevertheless, the burden of lung cancer attributable to SHS decreased from 1990 to 2019. At the sociodemographic index (SDI) district level, the middle-high SDI region had the greatest number of lung cancer deaths and DALYs attributable to SHS. Conversely, in high-SDI regions, the age-standardized mortality rateand age-standardized DALYs (age-standardized daly rate) rate of lung cancer attributable to SHS exhibit the most rapid declines. Moreover, the burden of lung cancer was mainly distributed in East Asia. The burden of lung cancer attributable to SHS is heavier for men than for women. Conversely, significant absolute and relative inequalities in lung cancer burden attributable to SHS, as measured by the SDI, were observed, with a marked decrease in these disparities over time. Globally, the number of deaths and DALYs is projected to increase, while the age-standardized rates (ASR) for both mortality and DALYs are expected to decline annually through 2035. From 1990 to 2021, an upward trend in the absolute number of lung cancer deaths and DALYs attributable to SHS was accompanied by a concurrent downward trend in their ASR. Inequalities associated with the SDI narrowed across countries over time. While this study has limitations inherent to the GBD database, these findings nonetheless underscore the importance of policies that protect nonsmokers from SHS exposure.