Observational, retrospective analysis of the circadian variability of out-of-hospital cardiac arrest within days of the week

Abstract

Introduction Previous studies showed a significant difference in out-of-hospital cardiac arrest (OHCA) occurrence between days of the week, with its highest incidence from Saturday to Monday and lowest in the middle of the week (Tuesday to Friday). The aim of this study was to compare the diurnal variability of the occurrence of OHCA on the days with the highest and lowest incidence of the latter. Methods Retrospective analysis of 815 OHCA cases with presumed cardiac etiology in Opole (Poland), covering a 2-year period (2006-2007). Statistical evaluation of the circadian patterns of OHCA occurrence on days with the highest and the lowest OHCA prevalence. Results Circadian variability of OHCA incidence, assessed by comparing consecutive 3-hour intervals, was present on Saturday to Monday (p=0.04), but absent on Tuesday to Friday (p=0.08). Both analyzed periods differed in terms of the morning (09:00-11:00) peak of OHCA occurrence, which was clearly seen on Saturday-Monday, but absent in the mid-week (median 8.0 [7.0-10.0] vs 5.0 [5.0-6.5], p=0.03). Conclusions The occurrence of OHCA follows different patterns on Saturday to Monday versus the mid-week days, with a pronounced morning peak only on Saturday to Monday.