Nitrogen dioxide and hospital length of stay and cost for systemic lupus erythematosus in Hunan, China

Evidence of both epidemiological and clinical studies exploring the impact of nitrogen dioxide (NO2) on the systemic lupus erythematosus (SLE) disease activity have been contradictory. To evaluate the association between short-term NO2 exposure and length of hospital stay (LOS) and hospital cost of SLE and estimate the burden of disease attributable to NO2 exposure. We collected health data of SLE inpatients who were hospitalized at secondary and tertiary hospitals in Hunan province of China during 2017–2019. Daily ambient concentrations of air pollutants (O3, CO, NO2, SO2, PM2.5 and PM10) and other environmental factors were obtained from public repositories by linking to individual addresses and date of hospitalization. Mixed effect models were employed to assess the associations between LOS and hospital cost for SLE inpatients and NO2 exposures during the previous 1 to 21 days (lag1-lag21) before hospitalization. We further estimated excess LOS and hospital cost attributable to NO2 exposure according to China's and World Health Organization's air quality guideline (AQG) respectively. A total of 11,447 records from 221 hospitals were finally included in our study. After full adjustments, 1 μg/m3 increment of NO2 was significantly associated with 0.038 day increase in LOS (95%CI: 0.0159–0.0601, P = 0.0008) and 0.0384 thousand yuan increase in hospital cost (95%CI: 0.0017–0.0679, P = 0.0395) with a lagged effect of 7 days prior to admission. Based on the adjusted effects of lag7, controlling for short-term NO2 exposure according to AQG could avoid up to 1.47 thousand days of hospitalization and 1.35 million yuan of cost for SLE in Hunan province during 2017 to 2019. Excess LOS and substantial economic burden among SLE inpatients attributable to NO2 could be avoid if policies were implemented to reduce the exposure. [Display omitted] •Short-term exposure to NO2 increased length of hospital stay in SLE inpatients.•Controlling NO2 exposure reduced the economic burden of SLE in China.•Policies should be implemented to decrease NO2 pollution level in China.