“… out-of-hospital cardiac arrest (OHCA) is “an on-going public health issue with a high case fatality rate and associated with both patient and environmental factors,” including temperature. And recognizing the concern that exists over the potential impacts of climate change on human health, the two scientists set out to investigate the population attributable risk of OHCA in Japan due to temperature, and the relative contributions of low and high temperatures on that risk, for the period 2005-2014.
To accomplish their objective, Onozuka and Hagihara obtained OHCA data from the Japanese Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications, which data amounted to over 650,000 cases in the ten-year period from all across the 47 Japanese prefectures. Thereafter, using climate data acquired from the Japan Meteorological Agency, they conducted a series of statistical analyses to determine the temperature-related health risk of OHCA.
Results of their study, in the words of the authors, “showed that temperature accounted for a substantial fraction of OHCAs, and that most of [the] morbidity burden was attributable to low temperatures.” Indeed, out of the nearly 24 percent of all OHCAs that were attributable to non-optimal temperature, low temperature was responsible for 23.64 percent. The fraction of OHCAs attributed to high temperature, in contrast, amounted to a paltry 0.29 percent — a morbidity burden that is two orders of magnitude smaller than that due to low temperature.
In further breaking down the temperature-OHCA relationship, Onozuka and Hagihara also examined the impact of extreme vs moderate temperatures, as well as the effects of gender and age on OHCA risk. With respect to extreme vs moderate temperatures, as shown in the figure below, the two scientists report that “the effect of extreme temperatures was substantially less than that of moderate temperatures.” For gender, they determined the attributable risk of OHCA was higher for females (26.86%) than males (21.12%). For age, they found that the elderly (75-110 years old) had the highest risk at 28.39%, followed by the middle-aged (65-74 years old, 25.24% attributable risk) and then the youngest section of the population (18-64 years old, 17.93% attributable risk).”