Kim SR. Eur Heart J. 2021 Jul 1;42(25):2487-2497.

The correlation of the combined impacts of air pollution and physical activity (PA) with cardiovascular disease (CVD) is becoming one of the utmost significant public health issues in CVD-associated factors. No study has analysed yet the impacts of changes in PA combined with the impacts of air pollution on cardiovascular health. Young adults might be more sensitive to air pollution, especially as a result of increased exposure to air pollution when executing outdoor PA, which is a risk factor for CVD. Thus, Kim SR, et al. conducted a study which analysed the correlation of the combined impacts of air pollution and changes in PA with CVD risk in a large, nationwide database of young adults 20–39 years of age and also evaluated either the cardiovascular health advantages of changes in PA exceed the prospective harmful impacts of increased exposure to air pollution.

Between 1,486,758 Korean young adults aged among 20 and 39 years without a previous history of CVD, a total of 1,469,972 participants were enrolled. The annual average cumulative level of particulate matter (PM) was used to measure air pollution exposure. PA was estimated as minutes of metabolic equivalent tasks per week (MET-min/week) based on two consecutive health investigations from 2009 to 2012.

A total of 8706 CVD incidents happened in 8 779 364 person-years of follow-up. The mean (SD) age was 32.3 (4.8) years and 886 844 were men between 1 469 972 participants. About one-fifth of the participants were outlined as physically inactive (18% in the first health analysis and 16% in the second health analysis). A reduction in PA was correlated with a greater risk of CVD between participants with low-to-moderate levels of exposure to PM2.5. (Figure 1)

Figure 1: Association of the change in physical activity (metabolic equivalent task-min/week) with cardiovascular disease including coronary heart disease and stroke according to the level of particulate matter 2.5 among young adults.

Solid lines represent adjusted hazard ratios, and the shaded region indicates the 95% confidence intervals from restricted cubic spline regression. Restricted cubic splines were constructed with five knots located at the 5th, 25th, 50th, 75th, and 95th percentiles of the change in metabolic equivalent task-min/week. Adjusted hazard ratios (95% confidence interval) were calculated using Cox proportional hazards regression analysis after adjusting for baseline metabolic equivalent task-min/week, age, sex, district, household income, body mass index, smoking, alcohol intake, systolic blood pressure, fasting serum glucose, total cholesterol, and Charlson comorbidity index. The cut-off value of particulatematter 2.5 (low to moderate vs. high) was 26.43 lg/m3.

An increase in PA above 1000 MET-min/week showed a negative impact on cardiovascular health between participants exposed to high levels of PM2.5 or PM10. Actually, the substantial impact adjustment of the correlation among changes in PA and CVD risk was recognized with the level of PM2.5 exposure (p for interaction = 0.09, marginally attenuated). The correlation of the combined impacts of PM10 exposure and changes in PA with CVD exhibited similar findings and movements to that of PM2.5 exposure and changes in PA with CVD. (Figure 2)

Figure 2: Association of the change in physical activity (metabolic equivalent task-min/week) with cardiovascular disease including coronary heart disease and stroke according to the level of particulate matter 10 among young adults.

Solid lines represent adjusted hazard ratios, and the shaded region indicates the 95% confidence intervals from restricted cubic spline regression. Restricted cubic splines were constructed with five knots located at the 5th, 25th, 50th, 75th, and 95th percentiles of the change in metabolic equivalent task-min/week. Adjusted hazard ratios (95% confidence interval) were calculated using Cox proportional hazards regression analysis after adjusting for baseline metabolic equivalent task-min/week, age, sex, district, household income, body mass index, smoking, alcohol intake, systolic blood pressure, fasting serum glucose, total cholesterol, and Charlson comorbidity index. The cut-off value of particulatematter 10 (low to moderate vs. high) was 49.92 lg/m3.

Particiapants who decreased their PA from ≥1000 MET-min/week to 1–499 MET-min/ week [PM10 adjusted hazard ratio (aHR) 1.22; 95% confidence interval (CI) 1.00–1.48] and to 0 MET-min/week (physically inactive; PM10 aHR 1.38; 95% CI 1.07–1.78) showed an elevated risk of CVD (p for trend <0.01) as compared to the participants exposed to low-to-moderate levels of PM2.5 or PM10 who continuously engaged in ≥1000 MET-min/week of PA. Participants exposed to high levels of PM2.5 or PM10  showed increased risk of CVD with an increase in PA above 1000 MET-min/week. (Table 1 and 2)

Table 1: Hazard ratios for cardiovascular disease according to changes in physical activity stratified by the level of particulate matter 2.5 among young adults

Table 2: Hazard ratios for cardiovascular disease according to changes in physical activity stratified by the level of particulate matter 10 among young adults

Overall, the substantial impact modification of the correlation maong changes in PA and CVD risk was also recognized with the level of PM10 exposure (p for interaction = 0.01) (Graphical abstract)

Combined effects of air pollution and changes in physical activity with cardiovascular disease in young adults.

Reduction in PA showed consecutive increase of CVD risk in young adults exposed to low-to-moderate levels of PM2.5 or PM10, contrarily a large increase in PA in a high-pollution environment may adversely impact cardiovascular health. Thus, at least maintaining PA levels is suggested for young adults who are already physically active with exposure to low-to-moderate levels of air pollution.