title: Exposure to sub-chronic and long-term particulate air pollution and heart rate variability in an elderly cohort: the Normative Aging Study.
abstract: BACKGROUND
  Short-term particulate air pollution exposure is associated with reduced heart rate variability (HRV), a risk factor for cardiovascular morbidity and mortality, in many studies. Associations with sub-chronic or long-term exposures, however, have been sparsely investigated. We evaluated the effect of fine particulate matter (PM2.5) and black carbon (BC) exposures on HRV in an elderly cohort: the Normative Aging Study.
  
  
  METHODS
  We measured power in high frequency (HF) and low frequency (LF), standard deviation of normal-to-normal intervals (SDNN), and the LF:HF ratio among participants from the Greater Boston area. Residential BC exposures for 540 men (1161 study visits, 2000-2011) were estimated using a spatio-temporal land use regression model, and residential PM2.5 exposures for 475 men (992 visits, 2003-2011) were modeled using a hybrid satellite based and land-use model. We evaluated associations between moving averages of sub-chronic (3-84 day) and long-term (1 year) pollutant exposure estimates and HRV parameters using linear mixed models.
  
  
  RESULTS
  One-standard deviation increases in sub-chronic, but not long-term, BC were associated with reduced HF, LF, and SDNN and an increased LF:HF ratio (e.g., 28 day BC: -2.3% HF [95% CI:-4.6, -0.02]). Sub-chronic and long-term PM2.5 showed evidence of relations to an increased LF and LF:HF ratio (e.g., 1 year PM: 21.0% LF:HF [8.6, 34.8]), but not to HF or SDNN, though the effect estimates were very imprecise and mostly spanned the null.
  
  
  CONCLUSIONS
  We observed some evidence of a relation between longer-term BC and PM2.5 exposures and changes in HRV in an elderly cohort. While previous studies focused on short-term air pollution exposures, our results suggest that longer-term exposures may influence cardiac autonomic function.
authors.affiliation: Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Landmark Center, 401 Park Dr, Boston, MA, 02215, USA. imordukh@hsph.harvard.edu.
authors.forename: Irina
authors.initials: I
authors.lastname: Mordukhovich
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, MA, USA. bcoull@hsph.harvard.edu.
authors.forename: Brent
authors.initials: B
authors.lastname: Coull
authors.affiliation: Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Landmark Center, 401 Park Dr, Boston, MA, 02215, USA. ekloog@hsph.harvard.edu.|Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva, Israel. ekloog@hsph.harvard.edu.
authors.forename: Itai
authors.initials: I
authors.lastname: Kloog
authors.affiliation: Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Landmark Center, 401 Park Dr, Boston, MA, 02215, USA. petros@hsph.harvard.edu.
authors.forename: Petros
authors.initials: P
authors.lastname: Koutrakis
authors.affiliation: VA Normative Aging Study, Veterans Affairs Boston Healthcare System and the Department of Medicine Boston University School of Medicine, Boston, MA, USA. pantel.vokonas@va.gov.
authors.forename: Pantel
authors.initials: P
authors.lastname: Vokonas
authors.affiliation: Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, and Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. jschwrtz@hsph.harvard.edu.
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000633:toxicity*; D001900:Boston; D015331:Cohort Studies; D004781:Environmental Exposure; D006339:Heart Rate / Q000187:drug effects*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000633:toxicity*; D012307:Risk Factors; D053260:Soot / Q000633:toxicity; D014481:United States; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D053260:Soot; D001335:Vehicle Emissions