Table 4. Time-dependent survival analysis (overall survival), stratified by colon or rectal cancer, for non-users and users of aspirin.

	User/non-user	Patients ( n)	Person-years	Deaths	Rate ratio	P -value	Adjusted rate ratio a	P -value
Colorectal cancer
Aspirin postdiagnosisb	Non-user	1176	5059	610	Reference	0.005	Reference	0.015
	User aspirin	275	1258	114	0.75 (0.62–0.92)		0.77 (0.63–0.95)
Aspirin frequent users postdiagnosisb	Non-user	1451	5172	628	Reference	0.001	Reference	0.002
	Frequent user	234	1145	96	0.69 (0.56–0.86)		0.70 (0.57–0.88)
Aspirin prediagnosis and postdiagnosis	Non-user	1309	5184	627	Reference	0.5	Reference	<0.001
	User	819	3303	383	0.96 (0.84–1.09)		0.88 (0.83–0.94)
Colon cancer
Aspirin postdiagnosisb	Non-user	748	3112	397	Reference	<0.001	Reference	0.001
	User aspirin	172	823	65	0.62 (0.48–0.80)		0.65 (0.50–0.84)
Aspirin frequent users postdiagnosisb	Non-user	772	3194	406	Reference	<0.001	Reference	0.001
	Frequent user	148	741	56	0.59 (0.45–0.79)		0.61 (0.46–0.81)
Aspirin prediagnosis and postdiagnosis	Non-user	843	3261	407	Reference	0.3	Reference	0.003
	User	533	2173	249	0.92 (0.78–1.08)		0.89 (0.82–0.96)
Rectal cancer
Aspirin postdiagnosisb	Non-user	428	1947	213	Reference	0.9	Reference	0.6
	User aspirin	103	435	49	1.03 (0.75–1.40)		1.10 (0.79–1.54)
Aspirin frequent users postdiagnosisb	Non-user	445	1978	222	Reference	0.5	Reference	0.7
	Frequent user	86	404	40	0.88 (0.63–1.23)		0.94 (0.65–1.34)
Aspirin prediagnosis and postdiagnosis	Non-user	466	1923	220	Reference	0.7	Reference	0.01
	User	286	1130	134	1.04 (0.84–1.28)		0.87 (0.78–0.97)

^aAdjusted for sex, age, comorbidity, year of incidence, grade, stage, chemotherapy (colon cancer), radiotherapy (rectal cancer) and surgery (all variables with P<0.05 in univariate analysis were entered in the multivariable analysis, together with sex and treatment). Median follow-up: 3.5 (0–12) years.

^bPostdiagnosis users are patients that used aspirin solely postdiagnosis and not prediagnosis.

The bold and italic entries indicate P<0.05.