Risk of Out-of-Hospital Cardiac Arrest in Aged Individuals in Relation to Cold Ambient Temperature - A Report From North Tochigi Experience.

Background: The impact of cold ambient temperature on out-of-hospital cardiac arrest (OHCA) in aged individuals caused by cardiovascular events in indoor environments has not been investigated sufficiently.

Methods and results: We conducted a case-crossover study. The relationship between OHCA caused by cardiovascular events and exposure to minimum temperature <0℃ was analyzed. Conditional logistic regression analysis was performed to estimate the odds ratios for the relationship between exposure to minimum temperature <0℃ and the risk of OHCA. Between January 1, 2011, and December 31, 2015, a total of 1,452 cases of OHCA were documented, and patients were screened for enrollment. A total of 458 individuals were enrolled in this analysis, and were divided into 2 groups of 110 (elderly group: 65-74 years old) and 348 (aged group: ≥75 years old). The aged individuals had a significant increased risk of OHCA after exposure to minimum temperature <0℃ (odds ratio [OR]: 1.528, 95% confidence interval [CI] 1.009-2.315, P=0.045). Cold ambient temperature was an especially significant increased risk for OHCA occurrence for males (OR: 1.997, 95% CI 1.036-3.773, P=0.039) and during winter (OR: 2.391, 95% CI 1.312-4.360, P=0.004) in the aged group.

Conclusions: Cold ambient temperature significantly affected aged individuals (≥75 years old) experiencing an OHCA caused by cardiovascular events in indoor environments.