Association between PM 2.5 exposure and heart rate variability for the patients with cardiac problems in Japan

A reduction in heart rate variability (HRV) is reportedly associated with an increased risk of cardiovascular mortality and morbidity. In previous studies, an inverse association was noted between HRV and particulate air pollution, but the sample populations were small and most consisted only of elderly individuals. We examined the association between 24-h HRV and fine particulate matter (PM2.5) in a large study population spanning 7 prefectures in Japan from April 2010 through March 2013. Meta-analysis was also performed. In total, 59,493 records of 24-h HRV for patients aged 20–90 years with symptoms/signs suggestive of heart disease were included in this analysis. Air pollution data were obtained from the National Institute for Environmental Studies. Regression models were used to examine the association between daily concentration of PM2.5 and HRV indices (e.g., standard deviation of normal-to-normal (SDNN), SD of average NN internals calculated over short periods (SDANN), very low frequency (VLF), and ultra-low frequency (ULF)). The model was adjusted for age, sex, temperature, and relative humidity. We examined the lagged association for single (up to lag3) and moving average (up to lag03). We found that decreases in HRV indices, especially for SDNN, SDANN, VLF, and ULF, were associated with PM2.5 in Hokkaido, Chiba, Tokyo, and Kanagawa. In contrast, there was no clear association between HRV with PM2.5 in Saitama and Aichi. Meta-analysis revealed significant decreases in SDNN, SDANN, VLF, and ULF were associated with PM2.5. Short-term exposure to PM2.5 was associated with lower 24-h HRV in patients with symptoms/signs suggestive of heart disease.