Influence of main air pollutants on hospital outpatient visits for cardiovascular and cerebrovascular diseases in Luoyang of Henan Province in 2016-2018

Background Cardiovascular and cerebrovascular diseases top the general causes of death among Chinese residents. However, current research focuses more on economically developed or heavily polluted areas, and the research results are inconsistent across regions.

Objective This study investigates the impact of major atmospheric pollutants (PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃) on the number of hospital outpatient visits for cardiovascular and cerebrovascular diseases in Luoyang of Henan Province from 2016 to 2018.

Methods Outpatient information of cardiovascular and cerebrovascular diseases, atmospheric pollutant concentration data, and meteorological data in Luoyang from January 1, 2016 to December 31, 2018 were collected. Generalized additive models (GAMs) were chosen to construct single-pollutant models, double-pollutant models, and stratified models of age, gender, and season. The relative risks (RRs) and 95% confidence intervals (CIs) of single-day and cumulative lag effects were estimated.

Results There were a total of 208355 cardio-cerebrovascular disease outpatient visits in Luoyang from 2016 to 2018. PM_2.5 and PM₁₀ daily concentrations exceeded the national standard limits for 277 and 82 d respectively, followed by NO₂, CO, and O₃ which were unqualified for 48, 9, and 8 d, respectively, and SO₂ did not exceed the standard. The single-pollutant models showed that the best lag days for PM_2.5, PM₁₀, SO₂, NO₂, CO, and O₃ were lag0, lag3, lag6, lag2, lag0, and lag04, and the corresponding RRs and 95% CIs were 1.002 4 (1.0011-1.0037), 1.0017 (1.0010-1.0025), 0.9767 (0.9696-0.9840), 1.0277 (1.0236-1.0319), 1.0006 (1.0004-1.0007), and 1.0041 (1.0014-1.0069), respectively. In the double pollutant models, there was no significant difference in the effect values of each pollutant before and after the introduction of other pollutants (P>0.05). The results of gender stratification and age stratification analyses showed that NO₂ was the most affecting pollutant. The best lag days of NO₂ on the outpatient volume of cardio-cerebrovascular diseases in men and women were lag2 and lag01, and the corresponding RRs and 95% CIs were 1.029 3 (1.023 5-1.035 1) and 1.027 7 (1.021 8-1.033 5), respectively. The best lag days of NO₂ affecting the number of outpatient visits of cardio-cerebrovascular diseases in patients aged 0-40, 41-65, and over 65 years were lag4, lag3, and lag2, and the corresponding RRs and 95%CIs were 1.0359 (1.0009-1.0720), 1.0277 (1.0215-1.033 9), and 1.031 1 (1.025 5-1.036 7), respectively. The results of seasonal stratification analysis showed that the maximum effects of PM_2.5, SO₂, NO₂, and CO appeared in spring, and the corresponding RRs and 95% CIs were 1.022 0 (1.018 8-1.025 3), 1.073 3 (1.057 0-1.089 9), 1.062 6 (1.053 1-1.0721), and 1.001 5 (1.001 1-1.001 9), respectively; the maximum effects of PM₁₀ and O₃ appeared in summer, and the corresponding RRs and 95% CIs were 1.0130 (1.0089-1.0171) and 1.018 4 (1.0133-1.0235), respectively.

Conclusion The increase in the concentration of major atmospheric pollutants (PM_2.5, PM₁₀, NO₂, CO, and O₃) in Luoyang from 2016 to 2018 may lead to an increase in the number of outpatient visits for cardio-cerebrovascular diseases. Among them, NO₂ may produce the highest risk. All these pollutants have lag effects.