New Delhi, May 1 : Long-term air pollution has now been found to be associated with an increased risk of arrhythmia or irregular heartbeat, researchers report. Air pollution is a modifiable risk factor for heart disease, but the evidence linking it with arrhythmia has been inconsistent to date. To determine whether there is a link, Chinese researchers evaluated hourly exposure to air pollution and the sudden onset of symptoms of arrhythmia using data from 2025 hospitals in 322 Chinese cities. Air pollution in China is well above the World Health Organisation's guidelines for air quality, and the researchers conducted their analyses using air pollutant concentrations from monitoring stations closest to the reporting hospitals. "We found that acute exposure to ambient air pollution was associated with increased risk of symptomatic arrhythmia," said Dr Renjie Chen, School of Public Health, Fudan University, Shanghai, China. The risks occurred during the first several hours after exposure and could persist for 24 hours. "The exposure-response relationships between 6 pollutants and 4 subtypes of arrhythmias were approximately linear without discernable thresholds of concentrations," Chen noted in a study published in the Canadian Medical Association Journal (CMAJ). The common arrhythmia conditions atrial fibrillation and atrial flutter, which can progress to more serious heart disease, affect an estimated 59.7 million people globally. The study included 190,115 patients with acute onset of symptomatic arrhythmia, including atrial fibrillation, atrial flutter, premature beats (originating in either the atria or ventricles of the heart) and supra-ventricular tachycardia. "Although the exact mechanisms are not yet fully understood, the association between air pollution and acute onset of arrhythmia that we observed is biologically plausible," the authors wrote. Some evidence has indicated that air pollution alters cardiac electrophysiological activities by inducing oxidative stress and systemic inflammation, affecting multiple membrane channels, as well as impairing autonomic nervous function, they added. /IANS