A cohort study on the causes of death in an endemic area of schistosomiasis japonica in Japan.

In order to elucidate the chronic effects of schistosomiasis japonica, a retrospective cohort study was carried out. The mortality experience of 2,067 inhabitants over 30 years old in the endemic area of schistosomiasis in Yamanashi Prefecture were followed up from 1958 to 1982 concerning the underlying cause of death. Total person-years at risk were 18,694.1 for males and 21,524.9 for females. The observed-expected ratio (O/E) was significantly high for cirrhosis of the liver (4.05 for males, 5.53 for females), cancer of the liver (males only, 2.30) and cancer of the colon (females only, 2.25). Increasing O/E values were observed for cirrhosis of the liver and cancer of the colon (females only) in relation to duration of residence in the area before 1957. These results suggest that schistosomiasis japonica is one of the important risk factors for cirrhosis of the liver, cancer of the liver and cancer of the colon.