Correlation between Hepatitis B Virus Infection and Chronic Liver Disease in Okinawa

Abstract

In Okinawa prefecture, prevalence of hepatitis B surface antigen (HBsAg) among blood donors is 3.5% and is twice as high as the average for the whole of Japan (1.5%), and is the highest in Japan (p<0.005). In contrast, mortality rates of both liver cirrhosis (LC) and primaryliver cancer (PLC) in Okinawa are the lowest in Japan. Many epidemiological studies have shown that the positive rate of HBsAg correlates with mortality rate of PLC. To elucidate the cause of this epidemiological discrepancy, cross-sectional seroepidemiological studies and a prospective clinical study were conducted.
In the cross-sectional studies, the following results were obtained;
(1) Positive rate of HBsAg among patients with LC in Okinawa was 15.2% and lowerthan the average for the whole of Japan (23.4%). A similar comparison among patients withhepatocellular carcinoma showed 24.4% in Okinawa Vs. 31.4% in the whole of Japan. (2) The age-specific hepatitis Be antigen positive rate among 829 HBsAg positive health examinees tend to decreasewith increase in age; 50% in<20 years old age group, 15.7% in third decade and 2-3% or less in 30 or more age group. Of the 829, 431 HBsAg positive subjects were referred our liver out-patient clinic.Then, of the 431, 27 (6.3%) were diagnosed or suspected as having chronic hepatitis and one (0.2%) was diagnosed as havingcirrhosis. Of the 431, 381 (88.4%) were diagnosed as healthy HBsAg carrier, the great majority (94.0%) of whom had positive reaction of and-HBe antibody and normal values of both GOT and GPT.
On the other hand, the prospective clinical study showed that; Among 24 initially HBeAg positive patients with chronic type B hepatitis, all of whom were followed-up for more than 12 months, 14 cleared HBeAg and subsequently 10 of the 14 acquired anti-HBe antibody. The cumulative clearance rate of HBeAg within the first two years was 56.3% and the annual clearance rateof HBeAg was 25.6%.
The tendency of early disappearance of HBeAg among HBsAg carriers during their life time or the course of chronic hepatitis might lead to the low death rate of hepatocellular carcinoma, particular that of HCC associated with hepatitis B virus infection in Okinawa.