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New Study Calculates Exactly How Bad Heat Is For Your Health

Heat and health: No sweat, right?

Lots of people complain about the weather, and if you believe climate scientists, we’re now all joining together to do something about it. People everywhere are racing into their cars, SUVs, and pickup trucks to make a personal contribution to the hot new trend: global warming.

Let’s assume for the moment that we take the word of all those scientists, and ignore the protests of politicians (who are surely better-informed and completely unbiased because they’re our elected representatives), is it really so bad if things warm up a bit?

This becomes a rather personally relevant issue for those of us living in Phoenix, where the temperature is expected to hit a balmy 115 degrees this weekend. A few years back, Steven MacFarlane and I did a study in which we measured how drivers responded to a car that blocked their passage through an intersection at a green light. When the weather was comfortably cool, the typical driver just politely tapped on their horn for a second. When it got up near 100, though, they started blaring their horns, yelling out the window, and making hand signals they probably did not learn in driver’s education. Craig Anderson and his colleagues have documented that the problem is more serious than just horn-honking. They’ve analyzed massive data sets to indicate that aggressive crimes of all kinds soar with the heat. When it gets bloody hot, it gets the blood flowing.

A new study by Purdue researcher Bo Li and her colleagues suggests that increasing heat may be even worse for our physical and mental health than we previously thought. As the researchers point out, a 1995 Midwest heat wave was linked to 700 deaths in Chicago, and a 2003 hot spell in Europe boosted the death rate by 70,000. Li and colleagues collected and analyzed data on weather and hospital admissions in Milwaukee Wisconsin for the years 1989 through 2005. They found that high temperatures were linked to increases in hospital admissions for a wide range of medical problems, including diabetes, urinary tract diseases, kidney stones, and respiratory ailments. There were also heat-related boosts in accidents and suicide attempts. According to a press release from the University of Wisconsin, where the study’s senior author Jonathan Patz is located, the effects of heat on health are worst for the very young (under 5 years old) and the very old (over 85).

According to Bo Li: “Unlike previous studies, we identified threshold temperatures for several health outcomes beyond which disease rates will increase rapidly,” For example, the research suggests that diabetes and kidney-related admissions will jump by 13 percent for every two degree boost in temperature above 85 degrees Fahrenheit.

As a consequence, the researchers point out that predicted changes in temperature over the next century will also be accompanied by boosts in demands on medical facilities. Of course, that’s if we don’t all die of heat stroke before then.


Anderson, C. A., Bushman, B. J., & Groom, R.W. (1997). Hot years and serious and deadly assault: Empirical tests of the heat hypothesis. Journal of Personality and Social Psychology, 73, 1213–1223.

Kenrick, D. T., & MacFarlane, S. (1986). Ambient temperature and horn honking: A field study of interpersonal hostility. Environment and Behavior, 18, 179–191.

Li, B., Sain, S., Mearns, L. O., Anderson, H. A., Kovats, S., Ebi, K. L., Bekkedal, M. Y. V., Kanarek, M. S. and Patz, J. A., The impact of extreme heat on morbidity in Milwaukee, Wisconsin (2011), Climate Change, published online June 8, DOI 10.1007/s10584-011-0120-y.

Study details how heat waves drive hospital admissions, Univ. of Wisconsion news. June 22, 2011.