Association between ambient air pollution and outpatient visits of cardiovascular diseases in Zibo, China: a time series analysis

Abstract

Introduction: Facing Mount Tai in the south and the Yellow River in the north, Zibo District is an important petrochemical base in China. The effect of air pollution on cardiovascular diseases (CVDs) in Zibo was unclear.

Methods: Daily outpatient visits of common CVDs including coronary heart disease (CHD), stroke, and arrhythmia were obtained from 2019 to 2022 in Zibo. Air pollutants contained fine particulate matter (PM_2.5), inhalable particulate matter (PM₁₀), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), and carbon monoxide (CO). Distributed lag non-linear models (DLNM) including single-pollutant model in single-day (lag0-lag7) and cumulative-days (lag01-lag07), concentration-response curve, subgroup analysis, and double-pollutant model were utilized to examine the relationships of daily air pollutants on CHD, stroke, and arrhythmia. Meteorological factors were incorporated to control confounding.

Results: In single-pollutant model, NO₂ was positively associated with CHD, stroke and arrhythmia, with the strongest excess risks (ERs) of 4.97% (lag07), 4.71% (lag07) and 2.16% (lag02), respectively. The highest ERs of PM_2.5 on CHD, stroke and arrhythmia were 0.85% (lag01), 0.59% (lag0) and 0.84% (lag01), and for PM₁₀, the ERs were 0.37% (lag01), 0.35% (lag0) and 0.39% (lag01). SO₂ on CHD was 0.92% (lag6), O₃ on stroke was 0.16% (lag6), and CO on CHD, stroke, and arrhythmia were 8.77% (lag07), 5.38% (lag01), 4.30% (lag0). No threshold was found between air pollutants and CVDs. The effects of ambient pollutants on CVDs (NO₂&CVDs, PM_2.5&stroke, PM₁₀&stroke, CO&stroke, CO&arrhythmia) were greater in cold season than warm season. In double-pollutant model, NO₂ was positively associated with CHD and stroke, and CO was also positively related with CHD.

Conclusion: Ambient pollutants, especially NO₂ and CO were associated with CVDs in Zibo, China. And there were strong relationships between NO₂, PM_2.5, PM₁₀, CO and CVDs in cold season.

Keywords: Zibo; ambient air pollutants; arrhythmia; coronary heart disease; stroke.

Figure 1

The location of Zibo District, Shandong Province, China.

Figure 2

Monthly variations of ambient air pollutants (NO₂, PM_2.5, PM₁₀, SO₂, O₃, and CO) in Zibo, China, 2019–2022.

Figure 3

Single excess risks (ER, 95%CI) in outpatient visits of CHD, stroke, and arrhythmia associated with NO₂, PM_2.5, PM₁₀, SO₂, O₃, and CO in single-pollutant model, at lag0-lag7.

Figure 4

Cumulative excess risks (ER, 95%CI) in outpatient visits of CHD, stroke, and arrhythmia associated with ambient air pollutants in single-pollutant model, at lag01-lag07.

Figure 5

Concentration-response curve between NO₂, PM_2.5, PM₁₀, SO₂, O₃, CO and the outpatient visits of CHD, stroke, and arrhythmia in single-pollutant model. The lags of NO₂, PM_2.5, PM₁₀, SO₂, O_3, and CO on outpatient visits of CHD, stroke, and arrhythmia: NO₂-CHD (lag07), NO₂-stroke (lag07), NO₂-Arrhythmia (lag02), PM_2.5-CHD (lag01), PM_2.5-stroke (lag0), PM_2.5-Arrhythmia (lag01), PM₁₀-CHD (lag01), PM₁₀-stroke (lag0), PM₁₀-Arrhythmia (lag01), SO₂-CHD (lag6), SO₂-stroke (lag0), SO₂-Arrhythmia (lag0), O₃-CHD (lag0), O₃-stroke (lag6), O₃-Arrhythmia (lag07), CO-CHD (lag07), CO-stroke (lag01), CO-Arrhythmia (lag0).