To Örebro University

Background: Hepatitis C is a slowly progressive disease mainly transmitted in people who inject drugs . This cohort has a high mortality from drug related causes, such as overdoses or external causes. We investigated the relative risk for liver related death in chronic hepatitis C (CHC) patients with or without illicit substance use disorders (SUD) .

Methods: Patients with CHC were identified using the Swedish National Patient Registry (contains all inpatient, day surgery, and outpatient non-primary care visits) according to the International Classification of Diseases-10 (ICD-10) code B18.2. The baseline observation was set to the first CHC visit from 2001, and person-time continued until death, emigration or December 31, 2013, whichever came first. Patients with ≥2 non-primary care visits with ICD-10 codes F11, F12, F14, F15, F16, or F19 were considered to have illicit SUD . The underlying cause of death was obtained from the Cause of Death Register . A six months lag-period between CHC diagnosis and death was introduced to reduce surveillance bias. Non-alcoholic liver disease was defined using ICD-10 codes K71–K77, B15–B19, B94.2, R17-R18, I85 .0, I98 .2, and I98 .3 . The relative risk for death was determined using standardized mortality ratio (SMR) where the observed number of deaths was divided by the expected number of deaths taken from five comparators from the general population (matched for age/sex/place of residency) .

Results: In total 38,186 patients with CHC were included in the study whereof 11,818 (31%) were considered to have illicit SUD . The CHC patients with SUD were younger (37 .7 vs . 46 .9 years) with a greater proportion of men (72% vs . 62%) than CHC patients without SUD . The SMRs for CHC patients with SUD were 10 .5, 33 .8, 18 .1, 123 .2, 61 .6, and 13 .2, for all-causes, liver cancer, alcoholic or non-alcoholic liver disease, drug-related, or external causes, respectively (Table 1) . The corresponding SMRs for CHC patients without SUD were 4 .1, 52 .8, 18 .0, 69 .4, 11 .2, and 4 .9, respectively (Table 1) .

Conclusion: The relative risks for all investigated parameters were elevated for CHC patients whether they had illicit SUD or not . Furthermore, although the CHC patients with SUD had a high relative risk to die from both drug-related and external causes, the relative risk to die from non-alcoholic liver disease was also greatly elevated .