Declines in heart rate variability associated with short-term PM2.5 exposure were modified by blood pressure control and treatment: A multi-city panel study in China*

Exposure to fine particulate matter (PM2.5) was associated with altered heart rate variability (HRV). However, whether blood pressure (BP) control and angiotensin II receptor blocker (ARB) treatment modifies the associations was seldom addressed. Therefore, we conducted a 3-phase panel study among 282 hypertensive subjects aged 35-74 years in four cities of China to address this issue. Real-time personal PM2.5 sampling and 24-h ambulatory electrocardiogram monitoring were performed repeatedly in 3 different seasons. Linear mixedeffects models were fitted overall and by control status of BP and ARB treatment to assess the associations between short-term PM2.5 exposure and HRV. The average hourly PM2.5 concentrations (Mean +/- SD) ranged from 19.3 +/- 18.2 mu g/m3 to 99.4 +/- 76.9 mu g/m3 across study phases and cities. Generally, PM2.5 exposure was associated with decreased hourly and 24-h HRV. However, these adverse impacts were attenuated among patients with controlled BP (<140/90 mmHg). For each 10 mu g/m3 increment in moving average of previous 2 days' (MA2d) PM2.5 exposure, 24-h SDNN (standard deviation of NN intervals) and rMSSD (root mean square of successive RR interval differences) decreased by 0.89% (95% CI: 0.19%-1.59%) and 2.98% (95% CI: 1.04%- 4.89%) among patients with uncontrolled BP (>= 140/90 mmHg), whereas no obvious declines were observed among those with controlled BP (Pdifference = 0.007 and 0.022, respectively). Furthermore, ARB treatment alleviated or eliminated PM2.5-associated declines in hourly and 24-h HRV among those with uncontrolled BP. For instance, 24-h SDNN decreased by 1.31% (95% CI: 0.54%-2.07%) with a 10 mu g/m3 increment in lag 2 days' PM2.5 exposure in ARB nonusers, whereas no obvious changes were observed in ARB users (Pdifference = 0.021). In conclusion, although PM2.5 exposure would decrease HRV, better BP control and ARB treatment could attenuate these adverse impacts, which provides supporting evidence for alleviating autonomic dysfunction of hypertension patients living in areas with high-level PM2.5.

Automated summary

Exposure to PM2.5 was found to decrease HRV, but this effect can be mitigated in patients with controlled blood pressure or receiving ARB treatment. These findings suggest that better BP control and ARB treatment could help alleviate the adverse impacts of PM2.5 exposure on HRV.