Cancer Mortality in Northern Ireland

THE Health Advisory Council for Northern Ireland (1946) has drawn attention to the very great increase which has occurred in the cancer death rate during the last hundred years. When the Council's memorandum was prepared, the crude rate was four times larger than it was in the decade 1851-60. More recently, the Registrar-General for Northern Ireland (1949) has emphasized that until 1931, the annual number of certified cancer deaths was always less than that attributed to all forms of tuberculosis, whereas, since 1931 the reverse has been true. The annual number of registered cancer deaths continues to increase while that of registered tuberculosis deaths continues to decrease. Three factors were suggested, by the Health Advisory Council, which could have contributed to the increase in the cancer death rate-an ageing population, improvement in diagnosis, and better certification of cause of death. To these possibilities a fourth must be added-a real increase in the risk of an individual dying from a malignant growth. It is not easy to separate the effects of these contributory factors, but within certain limits the effect of the ageing population can be ascertained, either by comparing like age groups or by some process of age standardisation of mortality. Further, a more precise evaluation of the certified mortality trends can be made by considering the specific parts of the body affected. From a detailed study of cancer mortality in relation to age and site, the Registrar-General for England and Wales (1940) concluded that "Recent research has tended to show. .. that the causative factors of cancer are complex and the occupational and social conditions have very different relations with cancer mortality according-to the site of growth selected for study. .. Some years later, Stocks (1947) studied the regional differences in cancer mortality of specified sites; he found striking differences for some sites (e.g., the stomach and respiratory organs), anid also revealed that whereas in some instances (e.g., cancer of the lung) certified mortality was increasing, in others (e.g., cancer of the uterus in females and cancer of the cesophagus in relatively young males), it was decreasing; w%hile for a number of sites nio material change occurred over the last twenty years. In an important contribution to the literature, Crabtree (1941) studied the familial incidence of the disease and tentatively concluded that the incidence of fatal cancer was excessive among the parents and siblings of women with cancer of …