Comparison of hepatitis B virus genotype B and C patients in Japan in terms of family history and maternal age at birth

Abstract

Aim

Hepatitis B virus of genotypes B (HBV/B) and C (HBV/C) prevails in Japan and patients with HBV/B have been known to be older than those with HBV/C, but the reason has remained unknown. We aimed to clarify the reason by focusing on the family history of HBV infection.

Methods

In a total of 508 patients with chronic HBV infection, HBV genotype, patient age, and age of the mother at birth were compared.

Results

Patient age was significantly older in HBV/B than in HBV/C, and the patient percentage with a family history of HBV infection was lower in HBV/B. When comparing maternal age at birth between the two genotypes, there was no significant difference in the overall patient population, but the proportion of older birth group (≥26 years old) was significantly lower in HBV/B (38.7% vs. 59.3%, p = 0.048) in patients with a family history of HBV infection in both mothers and siblings whose HBV were considered to be transmitted vertically. There was a negative correlation between maternal age at birth and patient age in this group, reflecting the fact that the age of childbearing is increasing recently in Japan. Because patients with HBV/B experience hepatitis B e antigen seroconversion at an earlier age, it was considered that HBV/B has become harder to transmit vertically in recent decades.

Conclusion

The recent decrease in vertical transmission of HBV/B associated with an older childbearing age in Japan might be one of the reasons for the finding that HBV/B patients were older than HBV/C patients.