Chronic hepatitis B virus infection and mortality from non-liver causes: results from the Haimen City cohort study.

Background: Studies of chronic hepatitis B virus (HBV) infection in endemic populations have rarely documented causes of mortality other than liver disease and hepatocellular carcinoma (HCC).
Methods: We analysed all-cause mortality related to HBV infection, focusing on the deaths not related to liver disease in a prospective cohort of adults living in Haimen City, China, who were followed from 1992 to 2002. Death certificate data from 4590 deaths among 83 794 individuals were analysed. At cohort entry, 15.0% of the 58 454 male subjects and 10.7% of 25 340 female subjects were hepatitis B surface antigen positive [HbsAg(+)]. HCC and chronic liver disease were the major causes of death in both men and women in this population. The analysis focused on non-liver causes of death.
Results: When liver-related causes of death were excluded, there was still a significantly higher age-adjusted death rate among HBsAg(+) individuals. The relative risks (RRs) and 95% confidence intervals (CIs) for all non-liver deaths among HBsAg(+) subjects were 1.2 (1.1-1.3) in men and 1.4 (1.1-1.7) in women. Non-liver causes were further subdivided into cancer and non-cancer groups. For all non-liver cancers, the RR was 1.2 (1.0-1.4) for males and 1.7 (1.2-2.3) for females. Non-liver, non-cancer deaths had RRs of 1.2 (1.1-1.4) and 1.2 (0.9-1.6) in males and females, respectively.
Conclusions: HBV-infected individuals may be at increased mortality risk from non-liver causes. Possible reasons include a direct effect of HBV infection, changes in the host immune system as a cause or effect of chronic infection, and behavioural factors associated with HBV infection. Further studies are needed to confirm this finding.