Diurnal temperature range and cardiogenic out-of-hospital cardiac arrest: a Japanese nationwide Utstein registry analysis

Background Environmental temperature variability cause notable blood pressure fluctuations in the human body and can lead to cardiac arrest. Although bathing-related heat shock incidences have been documented by prefecture, few large-scale studies have examined the relationship between regional temperature differences and out-of-hospital cardiac arrest (OHCA). Purpose Using a nationwide Utstein registry, we evaluated whether regional differences in diurnal temperature range are associated with cardiogenic OHCA and resuscitation outcomes. Methods We analyzed 2,342,720 cases from the All Japan Utstein Registry Data between 2005–2023, focusing on individuals aged ≥65 years. Using historical meteorological data from the Japan Meteorological Agency, we compared the frequency of cardiogenic OHCA between regions with large winter temperature differences (highest minus lowest temperature) at the prefectural level (top five prefectures, 190,046 cases) and those with small winter temperature differences (bottom five prefectures, 176,512 cases). Multivariate logistic analysis was performed using Return of Spontaneous Circulation (ROSC) and survival with CPC 1 or 2 (favorable neurological outcome) as outcomes. Results Ten prefectures (119,842 cases) most frequently reported OHCAs during winter. Among these, the proportion of cardiogenic OHCA was significantly higher in regions with large temperature differences than in those with small temperature differences (69.47% vs. 59.72%, p < 0.0001). Prefectures with large temperature differences reported the highest incidence of cardiogenic OHCAs both during winter and throughout the year. In multivariate analysis, the large diurnal variation group was an independent predictor associated with outcomes (ROSC: odds ratio = 1.14 [95%CI: 1.11–1.17, p<0.0001], survival and CPC 1–2: odds ratio = 1.06 [95%CI: 1.01–1.11, p=0.02]). Conclusion Large diurnal temperature ranges were independently associated with cardiogenic OHCA and ROSC, while differences in favorable neurological survival were modest. These findings may reflect regional variation beyond patient characteristics.