Cohort and period effects in peptic ulcer mortality from Japan.

Japan's death rate from gastric ulcer is far higher than that in any other country. The time pattern of peptic ulcer mortality between 1937 and 1980 was analysed in order to find out whether gastric ulcer in Japan, compared with Europe, shows other epidemiologic features which may indicate a different type of gastric ulcer disease. The age-adjusted death rates of both ulcer types and sexes have continuously decreased. In spite of the much higher death rates in the years 1937-80, the mortality of gastric ulcer shows a similar cohort phenomenon both in Japan and in Europe. The Japanese generations born in the last quarter of the 19th century ran the highest risk of dying from peptic ulcer and carried it throughout their lives. The cohorts with a high risk for duodenal ulcer lag 10 yr behind those with a high risk for gastric ulcer. Male and female cohorts with the highest risk were born at the same time. The cohort effects of both ulcer types are superimposed by period effects. The most obvious period effect during 1946-50 is seen in the short-timed increase of the death rates in all age groups, both sexes, and both ulcer types. The similarities between Japan and Europe suggest that worldwide, at the same time, the same environmental factors have precipitated the risk of dying from gastric and duodenal ulcer.