Fine particulate matter results in hemodynamic changes in subjects with blunted nocturnal blood pressure dipping

Particulate matter with aerodynamic diameter of <2.5 μm (PM2.5) is associated with blood pressure and hemodynamic changes. Blunted nocturnal blood pressure dipping is a major risk factor for cardiovascular events; limited information is available on whether PM2.5 exposure-related hemodynamic changes vary with day-night blood pressure circadian rhythms. In this study, we enrolled 161 subjects and monitored the changes in ambulatory blood pressure and hemodynamics for 24h. The day-night blood pressure and cardiovascular metrics were calculated according to the sleep-wake cycles logged in the subject׳s diary. The effects of PM2.5 exposure on blood pressure and hemodynamic changes were analyzed using generalized linear mixed-effect model. After adjusting for potential confounders, a 10-μg/m(3) increase in PM2.5 was associated with 1.0 mmHg [95% confidence interval (CI): 0.2-1.8 mmHg] narrowing in the pulse pressure, 3.1% (95% CI: 1.4-4.8%) decrease in the maximum rate of left ventricular pressure rise, and 3.6% (95% CI: 1.6-5.7%) increase in systemic vascular resistance among 79 subjects with nocturnal blood pressure dip of <10%. In contrast, PM2.5 was not associated with any changes in cardiovascular metrics among 82 subjects with nocturnal blood pressure dip of ≥10%. Our findings demonstrate that short-term exposure to PM2.5 contributes to pulse pressure narrowing along with cardiac and vasomotor dysfunctions in subjects with nocturnal blood pressure dip of <10%.