Cancer Death Rates in Japan Contrasted with those in England and Wales and Canada

COMPARISONs between death rates from cancer of particular organs in countries such as Denmark, Holland, Britain, Canada and the United States of America have revealed such a measure of agreement in many instances that pronounced differences, when they do appear between countries having good diagnostic and registration services, are worthy of attention. If such differences cannot be explained by variations in terminology, classification, completeness of ascertainment, accuracy of death certification or facilities for treatment, a search for the underlying reasons for them may lead in the end to discovery of causes of the forms ofcancer concerned. For that reason it is worth while to call the attention of research workers to pronounced international differences in rates which appear to satisfy the above conditions, even though no explanation can yet be suggested. For a long time it had been noticed that Japan's death rate from breast cancer appeared to be very small in comparison with the rates in western countries, but it was not until about 1950 that serious attention began to be paid to this. In that year the deaths of females from all forms of cancer registered in Japan numbered 31,758, of which 1,419 or 41⁄2 per cent, were assigned to breast cancer. The corresponding proportion in England and Wales was 19 per cent. In a report to the World Health Organisation Training Course on Vital and Health Statistics for South West Pacific Areas in 1952, Professor Mitsuo Segi, by using the population of Japan by age groups in that year as standard, calculated age-adjusted death rates in 1949 from breast cancer in females in 8 countries to be as follows: Canada 19.3; New Zealand 19-0; England and Wales 18.7; U.S.A. and Netherlands 18-5; Denmark 17.9; Australia 17-2; Japan 3-3. This was commented upon in several papers read to the 5th meeting of the International Society of Geographical Pathology at Washington D.C. in 1954 (Transactions, 1955), and no reason has been suggested why understatement of breast cancer as underlying cause of death should be appreciably greater in Japan than in the other countries. Thus, Maisin and Langerock, from their analysis of the documentation on Racial Factors (1955), concluded that "in certain countries, as e.g. Japan, where we have every reason to believe that the documents at our disposal are especially well proved and studied, we are certain that cancer of the breast is particularly low . . . ". Statistics of cause of death in recent years in Japan in respect of persons dying in early and middle life must be regarded as comparable in their reliability with those of countries such as Britain, Norway, Holland and Canada, although this is probably not true of rates at ages after 70.