title: Associations between changes in city and address specific temperature and QT interval--the VA Normative Aging Study.
abstract: BACKGROUND
  The underlying mechanisms of the association between ambient temperature and cardiovascular morbidity and mortality are not well understood, particularly for daily temperature variability. We evaluated if daily mean temperature and standard deviation of temperature was associated with heart rate-corrected QT interval (QTc) duration, a marker of ventricular repolarization in a prospective cohort of older men.
  
  
  METHODS
  This longitudinal analysis included 487 older men participating in the VA Normative Aging Study with up to three visits between 2000-2008 (n = 743). We analyzed associations between QTc and moving averages (1-7, 14, 21, and 28 days) of the 24-hour mean and standard deviation of temperature as measured from a local weather monitor, and the 24-hour mean temperature estimated from a spatiotemporal prediction model, in time-varying linear mixed-effect regression. Effect modification by season, diabetes, coronary heart disease, obesity, and age was also evaluated.
  
  
  RESULTS
  Higher mean temperature as measured from the local monitor, and estimated from the prediction model, was associated with longer QTc at moving averages of 21 and 28 days. Increased 24-hr standard deviation of temperature was associated with longer QTc at moving averages from 4 and up to 28 days; a 1.9°C interquartile range increase in 4-day moving average standard deviation of temperature was associated with a 2.8 msec (95%CI: 0.4, 5.2) longer QTc. Associations between 24-hr standard deviation of temperature and QTc were stronger in colder months, and in participants with diabetes and coronary heart disease.
  
  
  CONCLUSIONS
  In this sample of older men, elevated mean temperature was associated with longer QTc, and increased variability of temperature was associated with longer QTc, particularly during colder months and among individuals with diabetes and coronary heart disease. These findings may offer insight of an important underlying mechanism of temperature-related cardiovascular morbidity and mortality in an older population.
authors.affiliation: Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Amar J
authors.initials: AJ
authors.lastname: Mehta
authors.affiliation: Exposure, Epidemiology and Risk Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, United States of America; The Department of Geography and Environmental Development, Ben-Gurion University of the Negev, Beer Sheva, Israel.
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, Boston, Massachusetts, United States of America.
authors.forename: Antonella
authors.initials: A
authors.lastname: Zanobetti
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Brent A
authors.initials: BA
authors.lastname: Coull
authors.affiliation: The VA Normative Aging Study, Veterans Affairs Boston Healthcare System, Boston, Massachusetts, United States of America; The Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America; Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Sparrow
authors.affiliation: The VA Normative Aging Study, Veterans Affairs Boston Healthcare System, Boston, Massachusetts, United States of America; Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
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, Boston, Massachusetts, United States of America; The Channing Laboratory, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D013696:Temperature