Chen, Jiu-ChiuanCavallari, Jennifer MStone, PeterChristiani, David2011-05-102007Chen, Jiu-Chiuan, Jennifer M. Cavallari, Peter H. Stone, and David C. Christiani. 2007. Obesity is a modifier of autonomic cardiac responses to fine metal particulates. Environmental Health Perspectives 115(7): 1002-1006.0091-6765http://nrs.harvard.edu/urn-3:HUL.InstRepos:4885967Background: Increasing evidence suggests that obesity may impart greater susceptibility to adverse effects of air pollution. Particulate matter, especially PM\(_{2.5}\) (particulate matter with aero-dynamic diameter ≤2.5 μm), is associated with increased cardiac events and reduction of heart rate variability (HRV).Objectives Our goal was to investigate whether particle-mediated autonomic modulation is aggravated in obese individuals.Methods We examined PM\(_{2.5}\)-mediated acute effects on HRV and heart rate (HR) using 10 24-hr and 13 48-hr ambulatory electrocardiogram recordings collected from 18 boilermakers (39.5 ± 9.1 years of age) exposed to high levels of metal particulates. Average HR and 5-min HRV [SDNN: standard deviation of normal-to-normal intervals (NN); rMSSD: square-root of mean squared-differences of successive NN intervals; HF: high-frequency power 0.15–0.4 Hz] and personal PM\(_{2.5}\) exposures were continuously monitored. Subjects with body mass index ≥ 30 kg/m\(^2\) were classified as obese. Mixed-effect models were used for statistical analyses. Results: Half (50%) of the study subjects were obese. After adjustment for confounders, each 1-mg/m\(^3\) increase in 4-hr moving average PM\(_{2.5}\) was associated with HR increase of 5.9 bpm [95% confidence interval (CI), 4.2 to 7.7] and with 5-min HRV reduction by 6.5% (95% CI, 1.9 to 11.3%) for SDNN, 1.7% (95% CI, –4.9 to 8.4%) for rMSSD, and 8.8% (95% CI, –3.8 to 21.3%) for HF. Obese individuals had greater PM\(_{2.5}\)-mediated HRV reductions (2- to 3-fold differences) than nonobese individuals, and had more PM\(_{2.5}\)-mediated HR increases (9-bpm vs. 4-bpm increase in HR for each 1-mg/m\(^3\) increase in PM\(_{2.5}\); p < 0.001). Conclusions: Our study revealed greater autonomic cardiac responses to metal particulates in obese workers, supporting the hypothesis that obesity may impart greater susceptibility to acute cardiovascular effects of fine particles.en-USair pollutionenvironmental healthheart rate variabilityobesityrisk factorssusceptibilityJournal Article2011-05-1010.1289/ehp.9609