Time series study on influence of sulfur dioxide exposure on hospitalization of chronic obstructive pulmonary disease in Lanzhou from 2016 to 2020

BackgroundIn 2021, chronic obstructive pulmonary disease (COPD) emerged as the forth leading cause of death in the world. However, the impact of air pollutants on COPD is still inconsistent across current studies. ObjectiveTo analyze the relationship between ambient sulfur dioxide (SO2) exposure and hospital admissions for COPD in Lanzhou, and to examine the modified effects of SO2 across different genders, age groups, and seasons. MethodsA total of 20718 hospital admission records for COPD were collected from Lanzhou between 2016 and 2020, alongside synchronized data on SO2 concentration and meteorological variables. A generalized additive model integrated with a distributed lag nonlinear model was used to assess the relationship and the lag effects between SO2 exposure and COPD admissions. Potential confounders, including meteorological factors, day-of-the-week effect, and holidays, were controlled for, with a maximum lag period set at 7 d. Two-pollutant models and sensitivity analyses were conducted to ensure robustness. Results are expressed as relative risks (RR) with 95% confidence intervals (95%CI). ResultsDuring the study period, the average daily number of COPD admissions was 11.34±7.03. The average mass concentration of SO2 was (23.72±12.35) μg·m−3. SO2 exposure was positively correlated with COPD admissions; specifically, each 10 μg·m−3 increase in SO2 concentration was associated with an RR of 1.440 (95%CI: 1.317, 1.573). Stratified analyses found that at a cumulative lag of 7 d, the RRs were higher among females, individuals aged ≥65 years, and during the cold season. Conversely, no significant increase in COPD admission risk related to SO2 was observed during the warm season. For every 10 μg·m−3 increase in SO2 concentration, the RR was 1.483 (95%CI: 1.311, 1.678) for females, 1.441 (95%CI: 1.311, 1.583) for those aged > 65 years， and 1.595 (95%CI: 1.313, 1.937) during the cold season. ConclusionShort-term exposure to ambient SO2 exposure in Lanzhou is associated with an increased risk of COPD admission. The association is more pronounced among females, the elderly (aged> 65 years) and during the cold season.