What was done
Based on daily meteorological data for the period 1 January 2003 through 31 December 2010 obtained from the China Meteorological Data Sharing System - which included daily mean temperature plus minimum and maximum temperatures collected from a single station located in the heart of the urban area of Guangzhou City (the largest metropolis in Southern China) - along with individual data for all 189,379 registered deaths that occurred over the same time period, which they obtained from the Guangzhou Center for Disease Control and Prevention, the authors examined the effects of Diurnal Temperature Range (DTR) on human mortality rates, as well as whether the effects were different for different individual characteristics, such as gender, age and education level.

What was learned
Yang et al. report finding "a linear DTR-mortality relationship, with evidence of increasing mortality with DTR increase," where "the effect of DTR occurred immediately and lasted for four days," such that over that time period, a 1°C increase in DTR was associated with a 0.47% increase in non-accidental mortality. They also found that "the elderly, females and residents with less education have been identified as more vulnerable to rapid temperature change within a single day." In addition, they indicate there was a joint adverse effect with temperature "when mean temperature was below 22°C, indicating that high DTR enhanced cold-related mortality."

What it means
In light of their several findings, the eight researchers speculate that the expected "decrease in DTR in future climate scenarios might lead to two benefits: one from decreasing the adverse effects of DTR [which is reduced due to greater warming at night than during the day], and the other from decreasing the interaction effect with temperature [which is expected to rise with greenhouse warming]."