Modelling the burden of hepatitis C infection among people who inject drugs in Norway, 1973-2030

Abstract

Background: Lack of Hepatitis C virus (HCV) incidence data in (Norwegian) high-risk groups impedes the ability to make informed decisions on prevention measures. Thus we rely on modelling to estimate the incidence and burden of HCV infections.

Methods: We constructed a compartmental model for HCV infections in Norway among active and former people who inject drugs (PWIDs). We based yearly transition rates on literature. The model was fitted to absolute numbers of hepatitis C associated cirrhosis, hepatocellular carcinoma (HCC) and death from national data sources (2000-2013). We estimated the number (95%CI) of HCV infections, cirrhosis, HCC and death and disability adjusted life years (DALYs) due to HCV infections in Norway, 1973-2030. We assumed treatment rates in the projected period were similar to those in 2013.

Results: The estimated proportion of chronic HCV (including those with cirrhosis and HCC) among PWIDs was stable from 2000 (49%; 4441/9108) to 2013 (43%; 3667/8587). We estimated that the incidence of HCV among PWIDs was 381 new infections in 2015. The estimated number of people with cirrhosis, HCC, and liver transplant was predicted to increase until 2022 (1537 people). DALYs among active PWIDs estimated to peak in 2006 (3480 DALYs) and decrease to 1870 DALYs in 2030. Chronic HCV infection contributes most to the total burden of HCV infection, and peaks at 1917 DALYs (52%) in 2007. The burden of HCV related to PWID increased until 2006 with 81/100,000 DALYs inhabitants and decreased to 68/100,000 DALYs in 2015.

Conclusion: The burden of HCV associated with injecting drug use is considerable, with chronic HCV infection contributing most to the total burden. This model can be used to estimate the impact of different interventions on the HCV burden in Norway and to perform cost-benefit analyses of various public health measures.

Keywords: Burden of disease; Hepatitis C; Intravenous substance abuse; Natural history of disease model; Norway; People who inject drugs.

Fig. 1

Compartmental model of hepatitis C (HCV) progression among people who inject drugs in Norway. HCV: hepatitis C; HCC: hepatocellular carcinoma

Fig. 2

Fitted estimated number (line) with reported numbers (dots) for various health states in Norway, 1973–2030. Health states: Hepatitis C (HCV) infection, cirrhosis, hepatocellular carcinoma (HCC), liver transplant (LT) and HCV associated mortality. Grey shaded area shows 95% confidence interval

Fig. 3

Estimated number of new hepatitis C infections among people who inject drugs in Norway 1973–2030. HCV: hepatitis C, PWID: people who inject drugs. 95% confidence interval are shaded

Fig. 4

Number of people in various health states among people who inject drugs in Norway, 1973–2030. Hepatitis C: HCV, PWID: people who inject drugs. Left shows active and right shows former PWIDs. Health states: HCV negative in dark green, acute HCV in orange, chronic HCV in purple, cirrhosis in pink, hepatocellular carcinoma in light green, received a liver transplants in yellow and cumulative mortality related to HCV. Yellow shaded area shows predictions

Fig. 5

Proportion of burden attributable to health states among people who inject drugs in Norway, 1973–2030. Hepatitis C: HCV, PWID: people who inject drugs. YLDs: years lived with disabilities; YLLs: years of life lost; DALYs; disability adjusted life years. Health states: acute HCV in dark green, chronic HCV in orange, cirrhosis in purple, hepatocellular carcinoma in pink, received a liver transplants in light green. Yellow shaded area shows predictions

Fig. 6

Burden of hepatitis C associated with injecting drug use per 100,000 population in Norway, 1973–2030. YLDs: years lived with disabilities in orange; YLLs: years of life lost in purple; DALYs; disability adjusted life years in green. Yellow shaded area shows predictions, using future population estimates calculated by Statistics Norway