The association between the day of the week of milestones in the care pathway of patients with hip fracture and 30-day mortality: findings from a prospective national registry – The National Hip Fracture Database of England and Wales

Table 6 The association between day of the week of death and inpatient stay. Models are presented with no adjustment, adjusted for sex, and adjusted for age and sex; 1430 days of interest, 4,239,788 bed days, 13,461 inpatient deaths

		Stratification	1 = No stratification			2 = Stratified by sex			3 = Stratified by age and sex
Seasonal	Model	Parametrisation	IRR	(95% CI)	P	IRR	(95% CI)	P	IRR	(95% CI)	P
Elapsed month	Day of the week	Sunday	1			1			1
		Monday	1.033	(0.969, 1.100)	0.322	1.037	(0.974, 1.104)	0.253	1.036	(0.973, 1.104)	0.267
		Tuesday	1.036	(0.972, 1.104)	0.273	1.036	(0.973, 1.102)	0.273	1.035	(0.971, 1.103)	0.289
		Wednesday	1.108	(1.041, 1.180)	0.001	1.111	(1.045, 1.182)	0.001	1.110	(1.043, 1.182)	0.001
		Thursday	1.041	(0.977, 1.109)	0.220	1.043	(0.979, 1.110)	0.192	1.042	(0.978, 1.110)	0.203
		Friday	1.047	(0.983, 1.116)	0.153	1.049	(0.985, 1.116)	0.136	1.048	(0.984, 1.117)	0.144
		Saturday	0.988	(0.927, 1.054)	0.716	0.991	(0.930, 1.056)	0.780	0.991	(0.930, 1.057)	0.791
	Weekend	Weekday	1			1			1
	Weekend	Weekend day	0.944	(0.909, 0.980)	0.003	0.944	(0.909, 0.979)	0.002	0.944	(0.909, 0.981)	0.003
Restricted cubic spline	Day of the week	Sunday	1			1			1
		Monday	1.033	(0.969, 1.100)	0.323	1.037	(0.974, 1.103)	0.257	1.036	(0.973, 1.104)	0.273
		Tuesday	1.034	(0.970, 1.101)	0.306	1.035	(0.972, 1.101)	0.284	1.034	(0.971, 1.101)	0.302
		Wednesday	1.103	(1.037, 1.174)	0.002	1.107	(1.041, 1.177)	0.001	1.106	(1.040, 1.177)	0.001
		Thursday	1.037	(0.974, 1.105)	0.257	1.040	(0.977, 1.107)	0.219	1.039	(0.976, 1.107)	0.231
		Friday	1.044	(0.980, 1.112)	0.187	1.045	(0.982, 1.112)	0.166	1.045	(0.981, 1.113)	0.175
		Saturday	0.986	(0.925, 1.052)	0.673	0.990	(0.929, 1.054)	0.744	0.990	(0.928, 1.055)	0.756
	Weekend	Weekday	1			1			1
	Weekend	Weekend day	0.946	(0.911, 0.982)	0.004	0.945	(0.911, 0.981)	0.003	0.946	(0.911, 0.982)	0.004

There was no significant evidence of an interaction between stratification variables and day of the week parameterisation (likelihood ratio test, P > 0.1), IRR = Incidence Rate Ratio, CI = Confidence Interval. Omnibus Wald test of day of the week, Elapsed Month seasonal specification: (No stratification) P = 0.0128; (Stratified by sex) P = 0.0096; (Stratified by age and sex) P = 0.0125. Omnibus Wald test of day of the week, Restricted Cubic Spline seasonal specification: (No stratification) P = 0.020; (Stratified by sex) P = 0.013; (Stratified by age and sex) P = 0.017. Omnibus Wald test for MTWTF day of inpatient stay are equal to one another, Elapsed Month seasonal specification (No stratification) P = 0.13, (Stratified by sex) P = 0.12, (Stratified by age and sex) P = 0.13, Omnibus Wald test for MTWTF day of inpatient stay are equal to one another, Restricted Cubic Spline seasonal specification (No stratification) P = 0.17, (Stratified by sex) P = 0.14, (Stratified by age and sex) P = 0.15

ISSN: 1741-7015