Short-term effects of gaseous pollutants on cause-specific cerebrovascular disease among patients with type 2 diabetes: case-crossover evidence from Beijing, China

Abstract Background: The association between gaseous pollutants and cerebrovascular morbidity has been widely studied; however, the association in patients with type 2 diabetes has remained unknown in developing countries.Methods: A time-stratified case-crossover design combined with a distributed lag nonlinear model was adopted to estimate the short-term effects of gaseous pollutants (nitrogen dioxide [NO2], sulfur dioxide [SO2], ozone [O3], and carbon monoxide [CO]) on cerebrovascular cases among patients with type 2 diabetes in Beijing. In addition, our study explored the variability across sex and age groups.Results: A total of 223,216 (male 57.6% and elderly 61.7%) cerebrovascular cases were reported from 2014 to 2018. The cumulative exposure-response curves were U-shaped for NO2, J-shaped for SO2, and V-shaped for O3 and CO. Extreme low-O3, low-CO and high-CO increased the risk of cerebrovascular morbidity, with the maximum relative risk (RR) of 1.14 (95% CI: 1.01-1.28) (1st vs median), 1.02 (95% CI: 1.01-1.03) (1st vs median) and 1.25 (95% CI: 1.09-1.45) (99th vs median), respectively, appearing at lag0-13. Elderly individuals aged over 65 years were susceptible to extremely low-O3 (maximum RR: 1.27, 95% CI: 1.08-1.48). Men and elderly individuals were more susceptible to extremely high-CO, and the maximum RR was 10% [1.31 (1.11-1.54) vs. 1.19 (1.00, 1.41)] and 26% higher [1.41(1.17-1.69) vs. 1.12 (0.97, 1.30)] than women and adults, respectively. Conclusions: NO2, SO2, O3 and CO presented nonlinear and lagged effects on cerebrovascular disease among patients with type 2 diabetes, which may vary by sex and age. Our study added to the limited evidence for the risk of cerebrovascular disease due to gaseous pollutants among patients with comorbid type 2 diabetes.