胃がんの疫学

AN EPIDEMIOLOGICAL REVIEW OF STOMACH CANCER

Ⅰ．はじめに

　疫学的研究態度とは集団の中で展開する疾病の流行現象を時間的，空間的な場（すなわち環境）で観測し，解析することによりその疾病のHost-Agent-Relationshipを明らかにすることである¹⁾．

　したがって，胃がんの疫学的研究でも，環境，宿主および病因について追求し，流行像を把握するとともに，最終的には，それらの相互関係を解明することにある．

　しかし，がんにあっては，これまでの伝染性疾患や栄養欠乏症などとことなり，一つの要因が決定的な病因となりうることは考えられず，むしろ各種要因が複雑にからみ合った複合因子（Complex Factors）として発がんに関与するものとみられる．

　そこで，胃がんの疫学的探究により，これまでに得られた知見を各要因ごとに簡単にまとめてみた．

　The epidemiology of gastric cancer is a study to elucidate the relationship between environment, host and the cause of the disease by analysing epidemiological phenomena of gastric cancer developing among large aggregates of people, based on their observation from the view-point of time and space.

　In this respect, the author summarized some epidemic factors in the development of gastric cancer in this paper.

　Considered in the light of global epidemiological approach, it has been found that there are high incidences of gastric cancer in such northern nations as Japan, Chile, Iceland, U.S.S.R. and so on. On its socio-economic environment, it is recognized that the incidence of stomach cancer is higher in the people of low social class than in that of high social strata.

　One of the most important factors in the evolution of stomach cancer is the problem of diet. A fact is found that people in high incidence region take more starch foods, such as potatoes, rice and bread, and fewer fresh fruits and vegetables as compared with people of low incidence regions. Attention must also be paid to trace of carcinogenic substances contained in foods as well as to dietary habits or nutritional problems.

　As for the factors for cancer development on the host side, there are race, sex, heredity and constitution (such as blood type) that must be taken into account. Investigations by a psycho-somatic approach led the author to recognize that patients of stomach cancer have, generally speaking, poor outlet for emotional discharge and are of anti-neurotic type as compared with those of gastric ulcer. Therefore, the author suspects that there are some connections between suffering from stomach cancer and low activity of the hypophysio-adrenal function.