UNLABELLED: Liver mortality among individuals with chronic hepatitis C (CHC) infection is common, but the relative contribution of CHC per se versus adverse health behaviors is uncertain. We explored data on spontaneous resolvers of hepatitis C virus (HCV) as a benchmark group to uncover the independent contribution of CHC on liver mortality. Using national HCV diagnosis and mortality registers from Denmark and Scotland, we calculated the liver mortality rate (LMR) for persons diagnosed with CHC infection (LMRchronic ) and spontaneously resolved infection (LMRresolved ), according to subgroups defined by age, sex, and drug use. Through these mortality rates, we determined subgroup-specific attributable fractions (AFs), defined as (LMRchronic - LMRresolved )/LMRchronic , and then calculated the total attributable fraction (TAF) as a weighted average of these AFs. Thus, the TAF represents the overall fraction (where 0.00 = not attributable at all; and 1.00 = entirely attributable) of liver mortality attributable to CHC in the diagnosed population. Our cohort comprised 7,005 and 21,729 persons diagnosed with HCV antibodies in Denmark and Scotland, respectively. Mean follow-up duration was 6.3-6.9 years. The TAF increased stepwise with age. It was lowest for death occurring at <45 years of age (0.21 in Denmark; 0.26 in Scotland), higher for death occurring at 45-59 years (0.69 in Denmark; 0.69 in Scotland), and highest for death at 60+years (0.92 in Denmark; 0.75 in Scotland). Overall, the TAF was 0.66 (95% confidence interval [CI]: 0.55-0.78) in Denmark and 0.55 (95% CI: 0.44-0.66) in Scotland.

CONCLUSIONS: In Denmark and Scotland, the majority of liver death in the CHC-diagnosed population can be attributed to CHC-nevertheless, an appreciable fraction cannot, cautioning that liver mortality in this population is a compound problem that can be reduced, but not solved, through antiviral therapy alone.