Geophysical , Cultural and Behavioral Differences between High and Low Risk Areas of Gastric Cancer in Liaonin Province in China

Geophysical and socio-medical backgrounds including dietary habits between high risk and low risk areas of gastric cancer in Liaonin Province, China, were compared and analysed. Case-control study on psychobehavioral factors was carried out. The characteristics of high risk area was acid brown soil, drinking water with high nitrates, high rate of illiterates, unfavorable eating behavior and frequent intake of salty foods and foods with mutagens. Psychobehavioral factors may associate with higher incidence of gastric cancer.


INTRODUCTION
Marked differences in mortality rates of gastric cancer between counties in Liaonin Province were repeatedly reported before.We confirmed a significant regional differences in 43 counties of Liaonin Province, by examining age-adjusted death rates of stomach cancer in 1973-75 (1).Geophysical and socio-medical backgrounds between a high risk area and a low risk were compared for studying contributing factors of gastric cancer, and a role of psychobehavioral factors associated with gastric cancer were examined.
Two village were selected for comparison, one was Guanlu village, Zhuanghe county with high age-adjusted gastric cancer mortality of 59.1/105, and the control was Zhangtun village, Xinmin Province with a mortality of less than 10/105 in 1982-83.
Total population was 22,544 for Guanlu and 16,251 for Zhangtun in 1982, and the ratio of male to female was 102.7 and 104.1 respectively.Low mobility rates of the inhabitants has been recorded before 1980 in both areas.Life expectancy was 70.96 for male and 72.62 for Meteorological records and geological data were obtained from Liaonin Meteorological Bureau and Geological Bureau respectively.Acidity of arable soil and water quality came from Liaonin Soil General Investigation Office and Hydrological station respectively.Published Mortality and Population statistics from Liaonin Governmental Offices were used for calculation.The interviewers, primary and/or secondary school teachers, who were trained under the guidance of epidemiologists had visited each family, and filled in the items of the questionnaire for health, lifestyles and other socio medical of all family members.The items of the questionnaire included name, sex, birth date, family relationship, occupation, marital status, residence status, income and other economic history, familial disease history, personal disease history, dietary habits (61 items of main foods and foodstuffs) and other living mode, behavior and psychological responses.
Case control study of gastric cancer had conducted in Zhuanghe at that time and the results of psychological factors, only, were analysed here.A sample of the inhabitants in both areas were medically checked up with blood specimens, and also endoscopic and/or pathologic examinations, if necessary.Mutagenecity tests were performed on several foods which were suspected as carcinogenic.

Meteorological Background
The meteorological factors were analysed in the two areas from 1951 to 1980, including atmospheric pressure, temperature, rain, humidity, mean ground temperature, hours of insolation and duration per year, and the no-frost period.
The results showed no significant difference in the above factors between two areas.

Kind of Arable Soil and pH Value in the Two Counties
As seen in Table 1, 68% of the area in Zhuanghe was brown soil with pH value 6.2, while 87% of the area in Xinmin was meadow soil with pH value 8.4.

Comparison of Educational Status
The inhabitants of 27.4% in Zhuanghe were illiterates and/or semi-illiterates.It was slightly higher than that in Xinmin, which was 18.37%.Intake Frequency of Main Foods and Foodstuffs (Table 4)

Behaviors at Table
Main staple food in Zhuanghe was maize, maizegruel with sodium carbonate and sweet potato, while kaoliang was main in Xinmin.Salty foods and fermented cabbage and noodles were more common in Zhuanghe than in Xinmin.Beans scallions and tomato were frequently taken in Xinmin than in Zhanghe, but more spinach and celery were taken in Zhuanghe.Table 4. Intake Rate (%) of Food in the Two Counties (10-30 years age)

Psychological
Responses from the Results of Case-control Study of Gastric Cancer (Table 5) One hundred gastric cancer patients and two hundreds controls were compared with in the items of psychobehavioral status.Gastric cancer patients have had more frequent in angry words at table, impulsive and excitable but less irritable inclination than the controls.Indifference was also more frequent in the patients than in the controls.

DISCUSSION
Gastric cancer in China has been the highest mortality of all cancers by site.The mean age at onset was young comparing that of Japan.Therefore, prevention of gastric cancer is still an important problem in these areas.This paper is to make clear geophysical and socio-medical backgrounds related to gastric cancer for planning prevention strategies.
In high risk area of Zhuanghe and low risk of Xinmin, gastroendoscopic and pathologic biopsy findings were shown in Table 6.
Chronic hyperplastic gastritis (CHG), was significantly high in Zhuanghe than in Xinmin.Chronic atrophic gastritis (CAG) and intestinal metaplasia were in general low in the observed population, but there observed large differences between two areas.In high risk area, three cases of gastric cancer were diagnosed in this series, but no case was found in Xinmin.Precancerous conditions were clearly high in the high risk area.It seemed to be worthwhile to compare socio-medical backgrounds of two areas, high and low.
As for geophysical backgrounds, 67.8% of the soil in Zhuanghe was brown soil with a mean pH of 6.2, while 87.11% of the soil in Xinmin was meadow soil with a mean pH of 8.4.Drinking water in Zhuanghe showed significantly high level of nitrates than that in Xinmin.These findings may suggest the effect of agricultural products (foods) and drinking water on gastric cancer.
Illiteracy is called as one of the indicators of poor socio-economic conditions and level of hygiene.It is closely related to occupational and living conditions and also dietary habits.The results was that Zhuanghe was higher in illiteracy than in Xinmin.
Behaviors at table and intake frequency of various foods and foodstuffs suggest poorer dietary conditions for the inhabitants in Zhuanghe.
Experimental studies showed mutagenicity in salted pork, salted fish, fermented maize and pickled chinese cabbage and noodles, especially salted porks showing strong mutagenicity when heated like cooking.
Serum beta-carotene level as one indicator of intake of green yellow vegetables was not different between both areas, but intake amount of green-yellow vegetables was higher in females than in males for both areas, And serum carotenoids concentrations were lower in males than in females.
Evaluation of psycho-behavioral responses to causation of gastric cancer is not so easy, although they say mental conditions are closely associated with gastric disorders.It was observed that some episodes such as angry words at table, impulsive, and excitable were higher in the cancer patients than the controls, and the irritable state was on the contrary lower in the patients group.These findings show the need to study furthermore, in relation to causation of gastric disorders.
Low socio-economic conditions are often associated with heavy physical labours, low grade of eduction, poor diet and nutrition, little chances for recreation.Psychological conditions do not seem to be good under these conditions.Poor knowledges of hygiene may promote troubles in stomach and other organs, and lead to precancerous conditions.
In these situations health education, especially with changing dietary habits, and avoiding other risky lifestyles seemed to be essential to reduce in incidence of stomach cancer at moment.

Table 1
Assay Results of Drinking Water in the Two Counties (Table 2)Water in Zhuanghe was weakly acidic, while in Xinmin was alkaline.The nitrate content in Zhuanghe was 20 times more than that in Xinmin, which was significantly different between two areas.

Table 3
shows three factors seemed to be related to gastric disorders, such as eating time for each meal, unpleasant atmosphere at table and tendency to take spoiled dishes which suggest contamination of foods.People in Zhunghe showed shorter eating time than those in Xinmin, which means simple and small number of dishes and less time to eat.Angry words at table and intake of spoiled dishes were frequent in Zhuanghe than in Xinmin.Angry words suggest many problems in daily life, and spoiled dishes mean poor socio-economic conditions and low grade of hygienic education.

Table 6 .
Gastroscopic Results of Pathological Biopsy