Epidemiology and Health

Volume 18 (2); December 1996

Original Articles

Comparisons of cholera bacilli positive and negative patients in symptoms and laboratory findings among 1991 cholera patients.: Hee Choul Ohrr, Sun Ha Jee, Kyu Sang Kim, Yun Hwan Lee; Korean J Epidemiol. 1996;18(2):713-181.

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Abstract: Abstract
Among 130 cholera patients treated in Seohae Hospital in 1991, 86 were cholera bacilli positive and remaining 44 were negative. All cholera bacilli 'positive' patients were confirmed bacteriologically by National Institute for Health team. Cholera related symptoms and laboratory findings were gathered by interviews and medical records surveys. Symptoms and some serological laboratory findings are compared between cholera bacilli 'positive' and 'negative' patients in 1991 cholera epidemic. Results are as follows: 1. There were no differences in symptoms distribution and in mean values of all serological laboratory tests done between two groups. These facts support that both cholera bacilli 'positive' and 'negative' patients are persons who have cholera bacilli infection. 2. The age distribution of the cholera bacilli 'negative' group tended to be much younger than that of 'positive' group. The infection source of this group is believed to be the environmental reservoir. This findings suggests that cholera bacilli 'negative' patients have the possibility of endemic characteristics. We think it is worth investigating Vibrio cholera antibody titers of people in area with frequent cholera epidemics in Korea.; Summary

A Descriptive Study on Epidemiological Characteristics of Homeless Patients.: Moon Hee Jung; Korean J Epidemiol. 1996;18(2):191-201.

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Abstract PDF: Abstract
The purpose of this study is to provide basic data for dealing with the medical problems of homeless patients in medical protection. To sampling by age, sex, and carried out on 2440 homeless patients who have been given medical treatment between Jan. 1 Dec 31 in 1994 in the municipal D hospital in Seoul. Thus medical records of 172 patients were selected as the target data of this study. The selected data were analyzed by means of CATS, t-test, ANOVA, Pearson correlation coefficients and multiple regression. Some significant results could be obtained as follows. 1. Epidemiological characteristics The average age of the patients was 40.59 : Their ages were distributed between 20 and 84, the median being 37. As for the admission season, winter overwhelmed any other season : 30.8 % of the patients were admitted in winter. 2. Medical characteristics The days of treatment had a tendency to increase in proportion to the ages of patients : age 20-30 group took the least (average 1.92 days) and age 51-60 group took the most (average 2. 35 days). When it comes to the degree of drinking, 66 out of 172 patients(38.8%) suffered from alcohol or drug abuse. All of them had more than two kinds of diseases and 47. 0% of them were admitted in winter. As for the number of diseases, those who had been admitted in winter and autumn had the most and the least ones respectively. From the view point of age, age 51-60 group had the most and age 31-40 group had the least diseases. Viewed from the point of the days of treatment, those who had been treated for more than two days had more diseases than those treated for one day. From the viewpoint of administrative measures, the group committed by the police had more diseases than the other group and the group who had been treated free of charge had more diseases than the other group. The number of diseases was very closely related to the degree of drinking(Pearson correlation coefficients 0.877): No less than 77.83% of the diseases could be explained by only age and the degree of drinking. The above results implies that the government measures for the homeless patients should be reconsidered. They should not simply be accommodated in the social welfare facilities with a view to maintaining the order of the society. Instead we should admit them as economically weak class and deal with their medical problems in the field of medical protection.; Summary

A Study on the Source of Cholera Epidemic of Korea 1995-1996.: Jong Koo Lee, Sang Soon Kim, Ho Hoon Kim, Hee Choul Ohrr, Moon Sik Kim, Key Dong Park, Chang Yong Hawang; Korean J Epidemiol. 1996;18(2):185-190.

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Abstract: Abstract
E1 tor cholera epidemic have been reported eight times in Korea since 1963. Researchers suspected unattempted importation of cholera bacteria from foreign countries or artificial germination by some people. No researchers have made hypotheses of environmental reservoir as the sources of cholera epidemics until in 1991 in Korea. This study focuses on the aquatic reservoir as the potential source of cholera epidemic. A total of 68 cholera patients were noted in 1995 and only two in 1996. Authors argue for aquatic reservoir as the source of 1995, 1996 cholera epidemic and designate sea fishes as the vehicle of cholera infection The national Institute of Health team cultured Vibrio cholera O1, from the samples of sea water from Kangwha county in September 1995. The sporadic Occurrence of cholera patients around the country who have not traveled out of town support aquatic environmental reservoir as the source of 1995, 1996 cholera epidemic in Korea.; Summary

A Study on the Effect of Symptoms to Diagnosis Interval on the Cancer Survival.: Hee Jung Kang, Hee Choul Ohrr, Hee Ok Kim, Sun Ha Jee, Tae Yong Shon; Korean J Epidemiol. 1996;18(2):160-172.

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Abstract PDF: Abstract
For many years, members of medical profession have believed that the shorter symptoms to diagnosis interval(SDI) might be related to early stages and that the prompt treatments might improve survival rates in cancer patients. But this notion has been challenged by many researches for many years. This study was conducted to investigate the effects of SDI on the cancer survival for 221 stomach cancer cases, 106 lung cancer cases, 74 liver cancer cases and 59 cervix cancer cases. These cancer cases are registered ones in Kanghwa Cancer Registery Program from 1987 to 1991. Relationships among SDI, stages of cancers, operation rates, and survival were analysed. Results are as follows: 1. SDI was not related to stages of cancer. There were no difference in the distribution of stages among five SDI subgroups. 2. This data did not support that SDI affects the survival of stomach cancer patients. The cancer stages did affect survival in stomach cancer patients though. 3. Our data did not support that SDI affects cancer survival. A Cox proportional hazard model showed that SDI does not play a important role in cancer survival controlling age, gender, stage and other variables in the model. Further studies are highly expected to clarify the relationships between SDI and cancer survivals. Researches with bigger sample size and more sophisticated variables would be needed.; Summary

Pilot Study on Hepatitis B of 6- to 7-year-old School Children in Seoul.: Yun Ju Kang, Young Jin Hong, Jong Hoe Kim, Heng Lee; Korean J Epidemiol. 1996;18(2):151-159.

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BACKGROUND
Recentry, the prevalence of HBsAg in children has been gradually decreased in Korea may be due to extensive vaccination. The object of this study is to identify the HbsAg positive rate in 6 to 7 year-old school children in Seoul and to outline the surveilance status of the HBsAg positive subjects.
METHODS
We analyzed HBV mass screening results of 120,106 6 to 7-year-old school children in Seoul. For 188 HBsAg positive children who complied with the follow up visit, we tested HBeAg, LFT and interviewed their parents. We also compared the questionnaire results of HbsAg positive group with those of 694 random-sampled HBsAg negative controls.
RESULTS
The overall HBsAg positive rate was 0.79%(0.81% in boys and 0.76% in girls). Children in poverty area showed significantly higher rate(1.04%) of HBsAg positivity than those in non-poverty area(0.77%). Among HbsAg positive children, 86.7% was also HBeAg positive and had higher ALT levels than those with negative HBeAg. More than 70% of parents of HBsAg positive children was not aware of their children's HBsAg status before the screening and 28.7% of mothers did not know their own HbsAg status. The complete vaccination rate of the HBsAg positive and HBsAg negative group were 75.5% and 77.4% respectively, which shows no significant difference. Having family history of HBV infection was significantly associated with HBsAg positive status(OR=32. 8).
CONCLUSIONS
The HBsAg positive rate in 6- to 7-year-old school children has decreased in Korea compared to the data from previous studies. However in the aspects of public awareness and health care compliance, there are much room for quality improvement. Above all, more rigorous and continuous surveilance system is required for antenatal and postpartum care.; Summary

Effects of Exposure-Confounder Misclassification and Criteria of Model Choice in Ecologic Studies.: Sun Hee Lee, Chung Mo Nam, Hung Wok Park; Korean J Epidemiol. 1996;18(2):142-150.

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Abstract PDF: Abstract
Ecologic studies are widely used in all fields of public health on account of accesibility of data. However, two problems related to these studies have been brought up. The first is ecological fallacy occurred in the course of interpreting the ecologic level of exposure-disease associations into individual level. The second is exposure isclassification which leads to serious bias. Nevertheless there is few methodologic study dealing joint effects of the two problems in ecologic study. This study was conducted to suggest an ecologic model not having an ecologic fallacy due to model linkage failure and a methodology for correcting the misclassification bias due to exposure-confounder misclassification. Finally, we suggest a criteria for the ecologic model selection. Main results are as follows: 1. A linear ecologic regression model has a serious ecological fallacy due to model linkage failure and the misclassification bias due to the exposure-confounder misclassification. 2. An interaction ecologic regression model has no ecological fallacy due to model linkage failure, but it is affected seriously by the exposure misclassification. However misclassification bias could be removed mathematically if the information related to the misclassification was known. 3. A log-linear ecologic regression model has an ecological fallacy due to model linkage failure. It is seriously biased as the individual risk ratio are increased, but relatively less affected by the exposure misclassification than interaction ecologic regression model. 4. One of the two ecologic regression model-interaction ecologic regression model and log-linear ecologic regression model- would be selected according to the information of individual risk ratio and exposure misclassification. But using a linear ecologic regression model should be avoided in any circumstance. The above results are only valid in case that there is no other source of ecological fallacy except model linkage failure. Also exposure and confounder are independent each other, measured binary, and having nondifferential misclassification. Since the above assumptions are somewhat strong in considering the real situations of ecologic studies, it is necessary to extend the scope of this study.; Summary

Problems and Suggestions for Improvement in Epidemiological Study of Coal Workers' Pneumoconiosis in Korea.: Im Goung Yun, Young Lim, Won Chul Lee, Kwang Ho Meng, Hyeong Woo Yim; Korean J Epidemiol. 1996;18(2):131-141.

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Abstract PDF: Abstract
Pneumoconisosis was the first reported occupational disease in korea and was the most common occupational disease until 1990. Nowadays pneumoconiosis is the second most common occupational disease which accounts for more than at least 40% of all the occupational diseases in Korea. Many studies have been carried out in the prevalence rate, incidence rate, and risk factors assessment of pneumoconiosis. Workers exposed to dust used to take health examination once annually by the Industrial Safety and Health Act(1981). The number of coal workers has steadily decreased due to coal rationalization projects which have been strongly driven by the government since 1988 and the occupational environment has been improving. So, the incidence rate of pneumoconiosis will probably be lower in the future. But a disease control system administed for patient control and compensation, which is not involved in epidemiologic studies may not figure out the prevalence rate, incidence rate, mortality rate and the extent of severity of pneumoconiosis. Several problems and expected solutions are mentioned here as follows: 1. workers exposed to dust and pneumoconiosis patients are under government control, but the retired workers are not. Since we evaluate only visiting retired workers, we don't know exactly the current status and whole scale of the retired workers. If possible, the construction of cohort in all the retired workers is needed. 2. Since most of pneumoconiosis patients retired from the work and had changed their job, it is difficult to figure out the prevalence rate of pneumoconiosis just depending on the annual health exam for those workers at risk. So, systemic control for all pneumoconiosis patients is needed. 3. It is difficult to diagnose the onset of pneumoconiosis. We make a decision the time when the patient is diagnosed with pneumoconiosis on its onset. It is difficult to estimate it, especially in the case of retired workers because we can evaluate only persons with respiratory symptoms. The solution of such a problem is construction of cohort in all of the retired workers. 4. Because the patients who died outside of hospital don't seem to be reported, the mortality rate of pneumoconiosis is underestimated. So, systemic control and follow-up observation for all pneumoconiosis patients is needed. 5. A definite severity classification criteria for pneumoconiosis hasn't been established in Korea. We should try to make one. 6. Since workers who had exposed to dust in various mines at least 1 yr are subject to pneumoconiosis laws, workers easily don't report their full dust exposure history. Therefore we can't obtain the exact lifetime dust exposure from administrative data. We should try to make basic raw data of whole dust exposure in workers. It's concluded that the construction of cohort in workers who are or were exposed to dust in various mines is required and epidemiologic study of pneumoconiosis should be carried out with the administrative control of pneumoconiosis side by side. With the database of these materials, we can speculate and devise the measure for the further affecting subjects who are presumed to be most common in manufacturing industries.; Summary

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