Abstract
BackgroundThe 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.MethodsThis 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.ResultsHigher 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.Conclusion/SignificanceIn 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.
Highlights
It is well established that increases and decreases in ambient mean temperatures are associated with mortality [1,2], and that elderly age, chronic disease including cardiovascular disease and diabetes mellitus, mental illness, sociodemographic characteristics, and social isolation may heighten susceptibility to temperaturerelated mortality [3,4,5,6]
We evaluated if changes in the daily mean temperature, and the daily standard deviation of temperature, were associated with heart-rate corrected QT interval (QTc) in a cohort of elderly males in the Boston Metropolitan Area
Ambient particulate pollutant concentrations were monitored at our Harvard Air Pollution Supersite located near downtown Boston 1 km from the exam site, and for the present analysis we considered evaluation of 4-hour lag black carbon (BC) exposure prior to visit, which was identified as a significant predictor of QTc in a previous analysis [34]
Summary
It is well established that increases and decreases in ambient mean temperatures are associated with mortality [1,2], and that elderly age, chronic disease including cardiovascular disease and diabetes mellitus, mental illness, sociodemographic characteristics, and social isolation may heighten susceptibility to temperaturerelated mortality [3,4,5,6]. Previous research has demonstrated associations between mean temperature, averaged over shorter and longer intervals, and markers of inflammation [14,15,16], hemodynamics [17,18], and cardiac autonomic function [19,20,21,22,23], which suggests that these pathways may be potential mechanisms of mean temperature-related cardiovascular morbidity and mortality It hypothesized by Hampel and colleagues [24] that ambient mean temperature may affect repolarization, including QT interval and T-wave abnormalities, which are associated with arrhythmic events and cardiovascular mortality [25,26,27,28]. 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
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