Impact of the academic calendar cycle on survival outcome of injured patients: a retrospective cohort study at a community emergency department in Japan

Table 3 Subgroup analysis of hospital mortality in injured patients across academic cycles

	No of patients			Univariable analysis		Multivariable analysis^a
	Total	Dead	Mortality rate (%)	OR (95% CI)	p	Adjusted OR (95% CI)	p
By physiological reserve
Age of > 55 years (n = 9693)
April–June (reference)^b	2319	131	5.6	0.906 (0.742–1.107)	0.335	0.990 (0.724–1.355)	0.952
July–March	7374	457	6.2
ISS of > 15 (n = 2974)
April–June (reference)^b	741	184	24.8	0.907 (0.749–1.099)	0.319	0.912 (0.677–1.228)	0.545
July–March	2233	596	26.7
GCS score of < 9 (N = 1052)
April–June (reference)^b	648	153	23.6	0.837 (0.629–1.112)	0.219	0.838 (0.560–1.253)^c	0.390
July–March	404	109	27.0
SBP of < 90 mmHg (n = 854)
April–June (reference)^b	206	137	66.5	1.231 (0.885–1.712)	0.216	1.693 (0.968–2.959)^d	0.065
July–March	648	400	61.7
By specialized intervention
Doctor car system dispatched (n = 2357)
April–June (reference)^b	618	121	19.6	0.910 (0.723–1.145)	0.422	1.010 (0.681–1.499)	0.961
July–March	1739	367	21.1
Emergency surgery (n = 3007)
April–June (Reference)^b	757	43	5.7	0.944 (0.663–1.344)	0.790	0.918 (0.565–1.493)	0.731
July–March	2250	135	6.0
Emergency ETI (n = 1253)
April–June (reference)^b	315	178	56.5	0.909 (0.702–1.176)	0.466	0.999 (0.699–1.426)	0.994
July–March	938	552	58.8
Off-hours presentation^e (n = 12,424)
April–June (reference)^b	3248	146	4.5	0.872 (0.721–1.054)	0.173	1.020 (0.735–1.417)	0.904
July–March	9176	470	5.1
By different definition
April vs. remaining months (n = 20,945)
April (reference)^b	1744	77	4.4	1.034 (0.814–1.313)	0.764	0.886 (0.576–1.361)	0.580
May–March	19,201	821	4.3

CI confidence interval, ED emergency department, ETI endotracheal intubation, GCS Glasgow coma scale, ISS injury severity score, OR odds ratio, SBP systolic blood pressure
^aAdjustment for the potential confounders of age, sex, ISS, GCS score, SBP, trauma etiology (blunt or penetrating), and admission phase (2002–2005, 2006–2009, 2010–2013, and 2014–2018) unless otherwise indicated
^bIn Japan, the academic cycle typically begins on 1 April each year. The first academic quartile therefore corresponds to April to June
^cCategorized GCS score (3, 4–5, 6–8, 9–12, and ≥ 13) was removed from the set of explanatory variables because of the model validation
^dCategorized SBP (1–49, 50–75, 76–89, and > 89 mmHg) was removed from the set of explanatory variables because of the model validation
^e6:01 pm to 8:00 am on weekdays plus all weekend hours

ISSN: 2052-0492