Ambient PM 2.5 Concentration and the Cardiovascular Response to Exercise Training: A Systematic Review and Meta-Analysis Across Global Pollution Gradients
Discuss this preprint
Start a discussion What are Sciety discussions?Listed in
This article is not in any list yet, why not save it to one of your lists.Abstract
Background
Exercise training is a cornerstone intervention for cardiovascular disease, yet large cohort studies have reported attenuation of physical activity benefits at elevated air pollution concentrations, creating uncertainty around exercise prescription in polluted settings where cardiovascular disease burden is greatest.
Objectives
To determine whether ambient PM 2.5 concentration modifies the cardiovascular benefits of structured exercise training, using a global sample of trials spanning a >100-fold pollution gradient.
Methods
We conducted a systematic review and multilevel meta-analysis of exercise training interventions reporting pre–post changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), peak oxygen uptake (VO₂max), or resting heart rate (HR) in adults. Annual ambient PM 2.5 concentrations (3.5–283 µg/m³) were assigned to each study location from CAMS ERA5 reanalysis data. Three-level random-effects models with cluster-robust variance estimation accounted for arms nested within studies. PM 2.5 meta-regression was conducted unadjusted and adjusted for world region, exercise mode, trial duration, and health condition, with subgroup analyses by exercise mode and hypertension status.
Results
Across 465 studies (27,629 participants), exercise training produced clinically meaningful benefits for all outcomes (SBP −6.1 mmHg, DBP −3.3 mmHg, VO₂max +3.2 ml/kg/min, HR −2.8 bpm; all p < 0.001), with benefits consistently larger in higher-pollution settings. Hypertensive participants showed the greatest improvements, particularly from aerobic exercise (SBP standardised mean difference 0.396 in the Low vs 1.020 in the High PM 2.5 stratum). Although aerobic and resistance training participants experience similar chronic ambient PM 2.5 exposure, only aerobic exercise showed a stratum gradient (interaction p = 0.074).
Discussion
Exercise training delivers clinically meaningful cardiovascular benefits at every pollution level tested. The larger benefits observed in higher-pollution settings reflect the greater cardiovascular risk burden of those populations, and hypertensive patients stand to gain the most, particularly from aerobic exercise.
