Paper Reviewed
Wang, Y., Bobb, J.F., Papi, B., Wang, Y., Kosheleva, A, Di, Q., Schwartz, J.D. and Dominici, F. 2016. Heat stroke admissions during heat waves in 1,916 U.S. counties for the period from 1999 to 2010 and their effect modifiers. Environmental Health 15:83.

Introducing their work, Wang et al. (2016) write that "a heat wave, characterized by a sustained period of extreme hot weather, is associated with increased mortality and morbidity, particularly among older adults," citing the studies of Semenza et al. (1999), Matthies and Menne (2009), Huang et al. (2011), Ye et al. (2012) and Bobb et al. (2014); and they go on from there to describe how they "conducted a large-scale national study among 23.5 million Medicare fee-for-service beneficiaries per year residing in 1,916 U.S. counties during 1999-2010," where "heat wave days, defined as a period of at least two consecutive days with temperatures exceeding the 97th percentile of that county's temperatures, were matched to non-heat wave days by county and week," after which they fit "random-effects Poisson regression models to estimate the relative risk (RR) of heat stroke admissions [to] county hospitals on a heat wave day as compared to a matched non-heat wave day."

This protocol revealed that (1) more severe and longer-lasting heat waves had higher RRs, that (2) there was "a lower RR among counties with higher central air conditioning (AC) prevalence" that increased with the passage of time, such that (3) heat stroke RR "declined substantially from 71.0 in 1999 to 3.5 in 2010."

As for what they conclude from these many observations, Wang et al. write that heat stroke risks that still remain "could be addressed through public health interventions at a regional scale to further increase central AC."

References
Bobb, J.F., Obermeyer, Z., Wang, Y., and Dominici, F. 2014. Cause-specific risk of hospital admission related to extreme heat in older adults. Journal of the American Medical Association 312: 2659-2667.

Huang, C., Barnett, A.G., Wang, X., Vaneckova, P., FitzGerald, G. and Tong, S. 2011. Projecting future heat-related mortality under climate change scenarios: a systematic review. Environmental Health Perspectives 119: 1681-1690.

Matthies, F. and Menne, B. 2009. Prevention and management of health haards related to heatwaves. International Journal of Circumpolar Health 68: 8-22.

Semenza, J.C., McCullough, J.E., Flanders, W.D., McGeehin, M.A. and Lumpkin, J.R. 1999. Excess hospital admissions during the July 1995 heat wave in Chicago. American Journal of Preventive Medicine 16: 269-277.

Ye, X., Wolff, R., Yu, W., Vaneckova, P., Pan, X. and Tong, S. 2012: Ambient temperature and morbidity: a review of epidemiological evidence. Environmental Health Perspectives 120: 19-28.