Characteristics and outcomes of accidental hypothermia in Japan: the J-Point registry.

Background: Accidental hypothermia (AH) has higher incidence and mortality in geriatric populations. Japan has a rapidly ageing population, and little is known about the epidemiology of hypothermia in this country.

Methods: We created an AH registry based on retrospective review of patients visiting the ED of 12 institutions with temperature ≤35°C between April 2011 and March 2016. The severity of AH was classified as mild (≤35, ≥32°C), moderate (<32, ≥28°C) or severe (<28°C). The relationship between in-hospital mortality and severity of AH was assessed using a multivariable logistic regression analysis.

Results: A total of 572 patients were registered in this registry and 537 patients were eligible for our analysis. The median age was 79 (IQR 66-87) years and the proportion of men was 51.2% (273/537). AH was more likely to occur in elderly patients aged ≥65 years (424/537, 80.0%) and in indoor settings (418/537, 77.8%). The condition most frequently associated with AH, irrespective of severity, was acute medical illness. A lower mean outside temperature was associated with a higher prevalence of AH, and particularly severe AH (p for trend <0.001). The overall proportion of cases resulting in in-hospital death was 24.4% (131/537), with no significant difference between severity levels observed in a multivariable logistic regression analysis (severe group (37/118, 31.4%) vs mild group (42/192, 21.9%), adjusted OR (AOR) 1.01, 95% CI 0.61 to 1.68; and moderate group (52/227, 22.9%) vs mild group, AOR 1.11, 95% CI 0.58 to 2.14).

Conclusion: Active prevention and intervention should occur for this important public health issue.