April 12, 2023
3 min read
- Increased active commuting was tied to reduced CVD and cerebrovascular disease risk for farmers in China with low air pollution exposure.
- Any health benefits were attenuated with high air pollution exposure.
Exposure to higher amounts of fine particulate matter air pollution may counteract the protective CV effects of active commuting and farming activity in China, researchers reported.
In an analysis of Chinese biobank data with more than 320,000 participants, researchers found that increased active commuting was associated with reduced risks for cerebrovascular disease and ischemic heart disease for both farmers and nonfarmers with lower fine particulate matter (PM2.5) exposure. However, the associations disappeared for those with higher PM2.5 exposure.
“Being physically active is a well-established protective factor for cardiovascular health. However, the inhaled dose of PM2.5 increases with ventilation frequency and exposure time during outdoor physical activity,” Jun Lv, PhD, professor in the department of epidemiology and biostatistics at Peking University School of Public Health, China, and colleagues wrote in The Lancet Planetary Health. “Long-term PM2.5 exposure has been associated with an elevated risk of CVD. To what extent the beneficial effect of physical activity can be offset and even turn into increasing CVD risk due to prolonged outdoor time and higher inhalation rates in settings with high PM2.5 concentrations remains a concern, with no clear conclusions.”
Modeling air pollution exposure
In a prospective study, Lv and colleagues analyzed data from 322,399 adults aged 30 to 79 years without CVD at baseline who participated in the China Kadoorie Biobank between 2005 and 2017. Researchers assessed active commuting and farming activity using questionnaires. To estimate annual average PM2.5 exposure, the researchers created a high-resolution satellite-based model during the study period and stratified participants according to PM2.5 exposure ( 54 g/m³ vs. < 54 g/m³). Researchers estimated HRs for incident cerebrovascular disease and ischemic heart disease by active commuting and farming activity.
Within the cohort, 118,274 participants were nonfarmers and 204,125 identified as farmers. Among the farmers, 2,985 reported no farming time and 201,140 were included in the farming activity analysis.
During a median follow-up of 11 years, researchers identified 39,514 cerebrovascular disease cases and 22,313 ischemic heart disease cases.
Among nonfarmers with exposure to annual average PM2.5 concentrations of less than 54 g/m³, increased active commuting was associated with lower risk for cerebrovascular disease. Compared with those who reported the lowest amount of active commuting, those reporting the highest amount of active commuting were 30% less likely to develop cerebrovascular disease (HR = 0.7; 95% CI, 0.65-0.76) and 40% less likely to develop ischemic heart disease (HR = 0.6; 95% CI, 0.54-0.66). Among nonfarmers with exposure to annual average PM2.5 concentrations of at least 54 g/m³, there was no association between active commuting and cerebrovascular disease or ischemic heart disease.
Increased cerebrovascular risk for farmers
Similarly, among farmers with exposure to annual average PM2.5 concentrations of less than 54 g/m³, increased active commuting was associated with reduced cerebrovascular disease risk (HR = 0.77; 95% CI, 0.63-0.93), as was increased farming activity (HR = 0.85; 95% CI, 0.79-0.92). However, among farmers with exposure to annual average PM2.5 concentrations of at least 54 g/m³, increases in active commuting were tied to elevated cerebrovascular disease risk (HR = 1.12; 95% CI, 1.05-1.19), as were increases in farming activity (HR = 1.18; 95% CI, 1.09-1.28).
Researchers noted that the associations differed significantly between PM2.5 strata (P for all interaction values < .0001).
“For participants with long-term exposure to higher PM2.5 concentrations, the cardiovascular benefits of active commuting were attenuated to the null among nonfarmers,” the researchers wrote. “Both active commuting and farming activity were even associated with increased cerebrovascular disease risk among farmers with exposure to higher PM2.5 concentrations. Our findings have policy implications for continuously improving air quality, with similar efforts put into rural and urban areas, to maximize the cardiovascular protective effects of physical activity in China.”