Background
The authors write that "few studies have assessed the potential effects of intraday variation in temperature (i.e., diurnal temperature range, DTR) on mortality," citing as examples of those that have done so, Kan et al. (2007), Cao et al. (2009) and Lim et al. (2011). And they say there has been even less attention given to potential lag effects on the DTR-mortality connection.

What was done
Seeking to determine what role this phenomenon might have played among the inhabitants of Guangzhou, a subtropical city in China, Yang et al. examined the effects of DTR on cause-/age-/education-specific mortality during 2003-2010. This they did by combining a quasi-Poisson regression model with a distributed lag non-linear model to examine the effects of DTR on mortality, after first controlling for daily mean temperature, air pollutants, season and day of the week.

What was learned
The eight researchers found that "a 1°C increase in DTR at lag 0-4 days was associated with a 0.47% increase in non-accidental mortality." In addition, they report that stroke mortality was most sensitive to DTR, and that "females, the elderly and those with low education were more susceptible to DTR than males, the youth and those with high education, respectively."

What it means
As ever more researchers explore this phenomenon, it is becoming ever more clear that recent global warming - where the rise of the minimum temperature has occurred at a rate three times greater than that of the maximum temperature over most of the world (Karl et al., 1984, 1991) - has actually helped to reduce temperature-related deaths, not only by the means described here, but also due to the fact that extreme cold yearly kills far more people than extreme heat, as may be readily verified by perusing the many materials we have archived under the general heading of Health Effects (Temperature) in our Subject Index.

References
Cao, J., Cheng, Y., Zhao, N., Song, W., Jiang, C., Chen, R. and Kan, H. 2009. Diurnal temperature range is a risk factor for coronary heart disease death. Journal of Epidemiology 19: 328-332.

Kan, H., London, S.J., Chen, H., Song, G., Chen, G., Jiang, L., Zhao, N., Zhang, Y. and Chen, B. 2007. Diurnal temperature range and daily mortality in Shanghai, China. Environmental Research 103: 424-431.

Karl, T.R., Jones, P.D., Knight, R.W., Kukla, G., Plummer, N., Razuvayev, V., Gallo, K.P., Lindseay, J., Charlson, R.J. and Peterson, T.C. 1984. A new perspective on recent global warming: asymmetric trends of daily maximum and minimum temperature. Bulletin of the American Meteorological Society 74: 1007-1023.

Karl, T.R., Kukla, G., Razuvayev, V.N., Changery, M.J., Quayle, R.G., Heim Jr., R.R., Easterling, D.R. and Fu, C.B. 1991. Global warming: evidence for asymmetric diurnal temperature change. Geophysical Research Letters 18: 2253-2256.

Lim, Y.-H., Park, A.K. and Kim, H. 2011. Modifiers of diurnal temperature range and mortality association in six Korean cities. International Journal of Biometeorology 56: 33-42.