High risk of non-alcoholic liver disease mortality in patients with chronic hepatitis C with illicit substance use disorder

Aims: Hepatitis C virus (HCV) is a slowly progressive disease, often transmitted among people who inject drugs (PWID). Mortality in PWID is high, with an overrepresentation of drug-related causes. This study investigated the risk of death in patients with chronic hepatitis C virus (HCV) infection with or without illicit substance use disorder (ISUD). Methods: Patients with HCV were identified using the Swedish National Patient Registry according to the International Classification of Diseases-10 (ICD-10) code B18.2, with <= 5 matched comparators from the general population. Patients with >= 2 physician visits with ICD-10 codes F11, F12, F14, F15, F16, or F19 were considered to have ISUD. The underlying cause of death was analyzed for alcoholic liver disease, non-alcoholic liver disease, liver cancer, drug-related and external causes, non-liver cancers, or other causes. Mortality risks were assessed using the standardized mortality ratio (SMR) with 95% CIs and Cox regression analyses for cause-specific hazard ratios. Results: In total, 38,186 patients with HCV were included, with 31% meeting the ISUD definition. Non-alcoholic liver disease SMRs in patients with and without ISUD were 123.2 (95% CI, 103.7-145.2) and 69.4 (95% CI, 63.8-75.3), respectively. The significant independent factors associated with non-alcoholic liver disease mortality were older age, being unmarried, male sex, and having ISUD. Conclusions: The relative risks for non-alcoholic liver disease mortality were elevated for patients with ISUD. Having ISUD was a significant independent factor for non-alcoholic liver disease. Thus, patients with HCV with ISUD should be given HCV treatment to reduce the risk for liver disease.