Table 4– Crude and adjusted rate ratios (RRs) of in-hospital death according to the day of stay, relative to weekdays^#, stratified by diagnosis, sex and year of admission time

	Friday stay		Weekend stay
	Crude RR	Adjusted^¶ RR (95% CI)	Crude RR	Adjusted^¶ RR (95% CI)
Hospitalisation diagnosis
COPD	1.05	1.06 (1.01–1.10)	1.09	1.09 (1.05–1.13)
Pneumonia	1.04	1.04 (1.00–1.09)	1.04	1.04 (1.00–1.08)
Sex
Male	1.07	1.07 (1.03–1.12)	1.08	1.08 (1.05–1.12)
Female	1.01	1.02 (0.97–1.07)	1.04	1.04 (1.00–1.08)
Calendar year of admission
1990–1995	1.08	1.08 (1.02–1.15)	1.07	1.07 (1.02–1.12)
1996–2000	1.02	1.02 (0.96–1.08)	1.06	1.05 (1.01–1.10)
2001–2007	1.05	1.05 (1.01–1.11)	1.08	1.07 (1.03–1.12)

COPD: chronic obstructive pulmonary disease. ^#: Monday–Thursday inclusive; ^¶: for age, sex, calendar year of admission, admission day (weekday, Friday or weekend), prior hospitalisation and the modified chronic disease score divided into quartiles with a fifth category to account for subjects with no medication information in the year prior to cohort entry.