Examining the diurnal temperature range enigma: why is human health related to the daily change in temperature?
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An increasing number of epidemiological studies are finding statistical evidence that diurnal temperature range (DTR) is positively correlated to human morbidity and mortality despite the lack of clear clinical understanding. We examine a 14-year daily time series of emergency department (ED) admissions to the University of Virginia Medical Center in Charlottesville, Virginia, relative to long-term climate records from the Charlottesville/Albemarle County Airport weather station and the Spatial Synoptic Classification. DTR has a consistent strong positive correlation (r ~ 0.5) with maximum temperature in all months but only a weak, negative correlation (r ~− 0.1) with minimum temperature except in late summer (r ~− 0.4). Warm season DTR is highest on dry air mass days with low dew point temperatures. Cool season DTR is unrelated to morning temperature. Using a distributed lag non-linear model with an emphasis on DTR and its seasonal variation, after stratifying the models by season, we find that ED visits are linked to extreme cold events (cold days and nights) and high DTR in the cold season. In the warm season, ED visits are also linked to high DTR, but these are cool, dry, and pleasant days. The existing confusion regarding interpretation of DTR impacts on health might be rectified through a more careful analysis of the underlying physical factors that drive variations in DTR over the course of a year.
KeywordsDiurnal temperature range Emergency department visits Seasonality Morbidity Distributed lag non-linear model Temperature variability Spatial Synoptic Classification
We extend our thanks to Jerry Stenger and Wendy Novicoff (University of Virginia) for their assistance with accessing the climate and health data, respectively, and Scott Sheridan (Kent State University) for running the SSC for Charlottesville. We greatly appreciate the feedback we received from two external reviewers as well as their time and effort in reviewing this research.
Compliance with ethical standards
Statement of informed consent
For this type of study, formal consent is not required as the subjects were de-identified and examined in aggregate.
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