RÉSUMÉ
Objective:The exact biological mechanism whereby exposure to ambient ozone(O3)may contribute to clinical onset of cardiovascular events remains unclear.In this study,we aim to examine the impacts of O3 exposure on cardiac arrhythmias and potential pathways involved through autonomic dysfunction and myocardial injury.Methods:Seventy-three non-smoking healthy adults were followed with 4 repeated measurements of 24-hour ambulatory arrhythmias,heart rate variability,ST-segment deviation,and blood pressure(BP)in Beijing,China,2014-2016.Generalized additive mixed models coupled with distributed lag nonlinear models were constructed to evaluate the associations and potential interlinks between O3 exposure and outcome measurements.Results:During the study period,24-hour average concentrations of ambient O3 were 47.4 μg/m3(ranging from 1.0 to 165.9 μg/m3).Increased risks of premature ventricular contraction and ventricular tachycardia were associated with interquartile range increases in O3 exposure during the last 5 days before each participant's clinic visit,with relative risks of 2.14(95％confidence interval[CI]:1.95 to 2.32)and 5.47(95％CI:3.51 to 7.43),respectively.Mediation analyses further showed that sympathetic activation,parasympathetic inhibition,and elevated BP levels,as well as heightened risks of ST-segment depression could mediate up to 47.74％of the risks of arrhythmias attributable to O3 exposure.Conclusion:Our results suggest that short-term exposure to ambient O3 could prompt the genesis of arrhythmias partially through worsening autonomic function and myocardial burden.
RÉSUMÉ
Objective:Evidence on potential cardiovascular benefits of personal-level intervention among the elderly exposed to high levels of particulate matter(PM)remains limited.We aimed to assess improvements in surrogate markers of cardiovascular injury in vulnerable populations at risks by using indoor air filtration units.Methods:We conducted a randomized crossover trial for 2 separate 2-week air filtration interventions in 20 households of patients with stable chronic obstructive pulmonary disease and their partners in the winter of 2013,with concurrent measurements of indoor PM.The changes in biomarkers indicative of cardiac injury,atherosclerosis progression and systemic inflammation following intervention were evaluated using linear mixed-effect models.Results:In the analysis,average levels of indoor PM with aerodynamic diameters＜2.5 μm(PM2.5)decreased significantly by 59.2％(from 59.6 to 24.3 μg/m3,P＜0.001)during the active air filtration.The reduction was accompanied by improvements in levels of high-sensitivity cardiac troponin I by-84.6％(95％confidence interval[CI]:-90.7 to-78.6),growth differentiation factor-15 by-48.1％(95％CI:-31.2 to-25.6),osteoprotegerin by-65.4％(95％CI:-56.5 to-18.7),interleukin-4 by-46.6％(95％CI:-62.3 to-31.0)and myeloperoxidase by-60.3％(95％CI:-83.7 to-3.0),respectively.Conclusion:Indoor air filtration intervention may provide potential cardiovascular benefits in vulnerable popu-lations at risks.