Table 3. Associations between colorectal cancer diagnosis and venous thromboembolism stratified by Charlson Comorbidity Index levels, according to earlier (⩽90 days) and later (between 91 days and 5 years) risk periods following colorectal resection, Denmark, 1995–2010.

Comorbidity stratum	Cohort	Subjects	VTE cases	Person-years	SIR (VTE cases/103 person-years)a	Standardised incidence rate difference (95% CI)	Adjustedb hazard ratio (95% CI)	Interaction contrast (95% CI)
⩽90 days after CRC resection
No comorbidity	Reference	124 340	48	30 556	1.8	1. ref	1. ref	1. ref
	CRC	25 261	148	5857	26.0	24.2 (19.9, 28.5)	16 (12, 22)
Mild comorbidity	Reference	32 737	20	8016	2.2	1. ref	1. ref
	CRC	6787	41	1494	27.4	25.2 (16.5, 33.9)	11 (6.4, 19)	1.0 (−8.7, 11)
Moderate comorbidity	Reference	30 014	29	7304	3.5	1. ref	1. ref
	CRC	6357	36	1374	23.9	20.4 (12.3, 28.4)	6.7 (4.1, 11)	−3.8 (−13, 5.3)
Severe comorbidity	Reference	4662	5	1121	3.8	1. ref	1. ref
	CRC	1265	8	263	24.8	21.0 (2.3, 39.7)	7.0 (2.3, 21)	−3.2 (−22, 16)
>90 days after CRC resection
No comorbidity	Reference	123 644	966	490 256	2.2	1. ref	1. ref	1. ref
	CRC	23 108	416	73 727	5.7	3.5 (2.9, 4.1)	2.9 (2.6, 3.2)
Mild comorbidity	Reference	32 325	389	115 772	3.2	1. ref	1. ref
	CRC	5805	107	17 137	6.1	2.9 (1.6, 4.1)	1.9 (1.5, 2.3)	−0.6 (−2.0, 0.7)
Moderate comorbidity	Reference	29 278	405	96 501	4.0	1. ref	1. ref
	CRC	5317	104	14 915	7.1	3.1 (1.5, 4.6)	1.7 (1.3, 2.1)	−0.4 (−2.1, 1.3)
Severe comorbidity	Reference	4436	91	12 465	6.7	1. ref	1. ref
	CRC	996	23	2350	10.1	3.4 (−1.2, 8.0)	1.4 (0.85, 2.1)	−0.1 (−4.7, 4.5)

Abbreviations: CI=confidence interval; CRC=colorectal cancer; SIR=standardised incidence rate; VTE=venous thromboembolism.

^aAge- and sex-standardised incidence rates, using the age and sex distribution of the CRC cohort as the standard.

^bAdjusted for age on index date (continuous), sex and calendar year of CRC diagnosis.