Introduction
Hepatitis C virus (HCV) infection is the leading cause of liver-related morbidity and mortality, and is also associated with increased risk of non-liver-related morbidities, including renal and cardiovascular diseases, and metabolic diseases such as type 2 diabetes.1–3 There is growing evidence in the literature that people affected by HCV have a greater risk of developing diabetes,4–7 despite some conflicting findings in previous population-based studies.8–10 Although the pathogenesis of HCV-related diabetes mellitus is less clear, some possible underlying mechanisms include the interaction of HCV core proteins with hepatocytes disrupting the insulin signaling cascade and impairing the pancreatic β-cell function involved in glucose metabolism.7 11 This leads to increased insulin resistance in individuals with chronic HCV infection. In addition, liver damage and inflammation caused by HCV infection in these individuals could further increase the risk of diabetes.12
It has also been suggested that the impact of HCV infection on diabetes mellitus may vary across different ethnic groups, as HCV-related morbidity and mortality differ by ethnicity.13 14 For instance, in a US study conducted among people with HCV infection, Latin American people had the highest prevalence of pre-diabetes, followed by African–American, and white people (70%, 50%, 12%, respectively).15 Studies based in the USA and Europe have shown significant ethnic disparities in the overall distribution of diabetes, with non-white people having a higher prevalence.16–19 Asian people had a high prevalence of cardiometabolic diseases such as type 2 diabetes and hypertension compared with other ethnic groups even at lower body mass index (BMI).16 The distribution of diabetes according to HCV infection status across different ethnic groups in Canada remains unknown. Major ethnic groups in Canada include people from South and East Asia; according to the 2016 Census, there were more than 6 million people in Canada who reported being of Asian ancestry, with Chinese and Indian being the two most commonly reported ancestries.20 In British Columbia (BC), close to 30% of the population are of Asian origins, most of whom are foreign-born,20 from countries that have a high prevalence of HCV.21
In BC, there have been more than 70,000 people diagnosed with HCV infection and about 460,000 people diagnosed with diabetes.22–24 As people living with HCV infection and diabetes concurrently have greater morbidity and mortality risks,6 7 25 identifying population subgroups with higher comorbidity of HCV infection and diabetes would serve as valuable evidence to inform targeted HCV screening and management strategies to reduce disease burden related to diabetes. This study analysed population-based data from the BC Hepatitis Testers Cohort (BC-HTC)26 to assess the impact of HCV infection on the incidence of type 2 diabetes, and to investigate the differing impact of HCV infection on diabetes risk across ethnic groups in BC.