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The Impact of Global-Warming-Induced Diurnal Temperature Range Reduction on Hospital Emergency Room Admissions in Beijing, China
Wang, M-z., Zheng, S., He, S-l., Li, B., Teng, H-j., Wang, S-g., Yin, L., Shang, K-z. and Li, T-s. 2013. The association between diurnal temperature range and emergency room admissions for cardiovascular, respiratory, digestive and genitourinary disease among the elderly: A time series study. Science of the Total Environment 456-457: 370-375.

The authors - four of whom are atmospheric scientists and five of whom work in the medical professions - write that "a large change in temperature within one day may cause a sudden change in the heart rate and circulation of elderly people, which all may act to increase the risk of cardiopulmonary and other diseases, even leading to fatal consequences." And they further note, in this regard, that "it has been shown that a rise of the minimum temperature has occurred at a rate three times that of the maximum temperature during the twentieth century over most parts of the world, which has led to a decrease of the diurnal temperature range (Karl et al., 1984, 1991)."

What was done
Realizing the significance of these related facts, Wang et al. decided to evaluate the short-term effect of diurnal temperature range (DTR) on emergency room (ER) admissions among elderly adults in Beijing." As they describe it, "after controlling the long-time and seasonal trend, weather, air pollution and other confounding factors, a semi-parametric generalized additive model (GAM) was used to analyze the exposure-effect relationship between DTR and ER admissions among elderly adults with different lag structures from 2009 to 2011 in Beijing," where they "stratified groups by age and gender."

What was learned
The nine researchers report that "significant associations were found between DTR and four major causes of daily ER admissions among elderly adults in Beijing." More specifically, they state that "a 1°C increase in the 8-day moving average of DTR (lag 07) corresponded to an increase of 2.08% in respiratory ER admissions and 2.14% in digestive ER admissions," while "a 1°C increase in the 3-day and 6-day moving average of DTR (lag 02 and lag 05) corresponded to a 0.76% increase in cardiovascular ER admissions, and a 1.81% increase in genitourinary ER admissions, respectively." And they add that "people aged 75 years and older were associated more strongly with DTR than the 65-74 age group."

What it means
The findings of Wang et al., combined with those of Karl et al. (1984, 1991), make it clear that the diurnal nature of the global warming of the past century or so has helped to reduce the incidence of many life-threating health problems of the elderly in Beijing, China, just as it has also done for many people, both old and young, in a number of other countries - including Australia (Xu et al., 2013), Hong Kong (Tam et al., 2009) and Korea (Lim et al., 2012) - as well as other parts of China (Kan et al., 2007; Yang et al., 2013).

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., Hong, Y.-C. and Kim, H. 2012. Effects of diurnal temperature range on cardiovascular and respiratory hospital admissions in Korea. Science of the Total Environment 417-418: 55-60.

Tam, W.W.S., Wong, T.W., Chair, S.Y. and Wong, A.H.S. 2009. Diurnal temperature range and daily cardiovascular mortalities among the elderly in Hong Kong. Archives of Environmental and Occupational Health 64: 202-206.

Xu, Z., Huang, C., Su, H., Turner, L.R., Qiao, Z. and Tong, S. 2013. Diurnal temperature range and childhood asthma: a time-series study. Environmental Health 12: 10.1186/1476-069X-12-12.

Yang, J., Liu, H.-Z., Ou, C.-Q., Lin, G.-Z., Zhou, Q., Shen, G.-C., Chen, P.-Y. and Guo, Y. 2013. Global climate change: Impact of diurnal temperature range on mortality in Guangzhou, China. Environmental Pollution 175: 131-136.

Reviewed 2 October 2013