Epidemiology and Health

Volume 16 (1); June 1994

Original Articles

Cohort Study.: Yong Tae Yum, Soon Duck Kim; Korean J Epidemiol. 1994;16(1):116-135.

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The cohort study is an observational epidemiological study which selects the specific study population attempting to study the relatiqnship between an exposure to the purported cause and the subsequent risk of developing disease in accordance of time direction. Since Doll and Hill had studied the association between lung cancer and smoking behavior among the British medical doctors in the years of the last fifties, the defined group cohort studies analysing the relationship between an exposure and the occurence of a disease have become very popular. Cohort studies can be classified as either prospective or retrospective, depending on the temporal relationship between the initiation of the study and the occurence of the disease. Cohort studies are admitted as the very valuable studies for demonstrating the association between an exposure and a disease because it is possible to drive relative and attributable risks and often incidence measures. They can even examine multiple effects of a single exposure. However, they are usually expensive to carry out and large cohorts are required for rare diseases in addition to the time consum ing works. There are also very significant problems associated with selection of appropriate groups to be studied as far as complete ascertainment of disease occurence in them. Usually it is necessary that we must compromise to provide the opportunity for various types of bias such as selection bias, follow-up bias, information bias or misclassification, confounding bias and post hoc bias to occur which can result in incorrect conclusions. Only the success of a cohort study would be expected when the investigator pay the deep care in recognizing and correcting for these biases.; Summary

A Review Study on Health Impacts of Agent Orange.: Young Joo Park, Joung Soon Kim; Korean J Epidemiol. 1994;16(1):84-115.

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In order to understand epidemiologic characteristics of dioxins related health impacts, 107 diox in-related literatures published up to May, 1993 were thoroughly reviewed. The results obtained are as follows: 1. Review studies on dioxins can be classified into two types : one is studies concentrated on one specific subject related to dioxins such as the effects on skin, birth outcomes, metabolic machanisms in the human body, major sources of exposure to the general population, immunotoxicity, association between dioxins and cancers, and research methods on effects of dioxins. The other is review studies dealing with overall aspects of dioxins, among which the report published by Academy of Science of United Stateds of America in 1993 is the most recent one. 2. Judging by consistency of results and biological plausibility, there were three groups of diseases ; diseases having causal relationship, having possibilities of causal relationship, and having no causal relationship for the time being. 1) The diseases showing causal relationship were lung cancer, Hodgkin 'disease, non-Hodgkin 'lymphoma, soft tissue sarcoma, chlordane, and polyneuropathy 2) the diseases showing possibilities of causal relationship were stomach cancer, lymphatic and haematopoietic cancer, multiple myeloma, skin cancer, diseases of digestive system, and CNS deformity among children born to the people exposed. 3) The diseases showing no causal relationship were oral and laryngeat cancer, esophageal cancer, prostate cancer, kidney cancer, bladder cancer, brain and CNS cancer, diseases of circulatory and respiratory systems. There were numerous diseases of digestive system, which showed difficulty in establishing definite causal relationship owing to the lack of consistency among researchers. 3. Even though papers dealt with dioxinrelated mortality and morbidity studies showed high mortality rate from accident, biological plausibility explaining causal relationship between them should be sought further. 4. There was a high prevalence of hearing loss among Vietnam veterans, and it seemed rather related to the explosive noise in combat than dioxin itself. 5. The current TCDD levels of Vietnam veterans were almost the same as those of the general population.; Summary

Epiderniologic Characteristics and Trends of Leptospirosis in Korea by Literature Review.: Sung Soo Kim, Joung Soon Kim; Korean J Epidemiol. 1994;16(1):66-83.

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In order to understand the epidemiologic characteristics and trends of Leptespirosis in Korea, year book of acute infectious disease and literatures published were thoroughly reviewed. The results obtained are as follows: 1. The outbreak of Leptospirosis in Korea has decreased during recent years. Most of the patients occured in Semptember, October, and November. Seventy nine percent of reported patients occured in north Choongchung, south Choongchung, and Kyunggi province in 1987-1991. 2. Leptospires isolation rates were ranged from 0.2% to 16.0% among normal healthy person, higher in rural residents than military personnels. 3. Total of 92 strains were isolated from human in six years from 1984 to 1990. Its main serogroups were Icterhaemorrhagiae and Canicola, predominantly consisted of serovar lai, copenhageni and canicola. Eighteen strains of Biflexa were also isolated from healthy persons and patients. 4. The proportion of Leptospirosis among patients with acute febrile episode has decreased since 1985. Sero-positive rate of male among patients with acute febrile episode is higher than that of female. Sixty percent of sero-positive patients with acute febrile episode was older than 40-year of age. The seropositive rates were consistently the highest in harvest season than other seasons. Residents of north Choongchung, north Chunlla, south Chunlla, Kyunggi, and north Choongchung provinces showed higher seropositive rates than those of other ones. Main serogroups positive to most sera of Koreans were Icterohaemorrhagiae and Canicola. 5. The sero-positive rate of normal healthy persons ranged from 2.0 to 25. 6% ; the sero-positive rate of rural area was 4 to 8 times higher than that of healthy urban people. Little difference was observed in sero-positive rate by age group among above 40 years old people, although it was higher in male by sex, in farmers by occupation and in some provinces by area.; Summary

Semiquantitative Food Frequency Method as an Epidemiological tool in a Rural community, Korea.: Mi Kyung Kim, Bo Youl Choi, Young Jeon Shin, Yoon Ok Ahn, Sang Sun Lee, Young Sun Cho; Korean J Epidemiol. 1994;16(1):54-65.

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This study was performed to evaluate the semiquantitative food frequency questionnaire used to obtain information about. dietary patterns of adults in a rural county, Yang-pyeung Gun. The study population was 1311 adults aged 17~85 years. And well-trained interviewers interviewed subjects in 1990, 1992, 1993. The results are as follows. 1) Nutrients intake calculated from each questionnaire showed significant difference, because the number of question was not same(fifty questions in 1990, eighty questions in 1992, 1993). 2) Estimated nutrients intake from separate food items was significantly different when food items are combined in one question. 3) The agreement of nutrients intake level except vit C were high when the subjects are cross-classified by their ranks on the nutrients intake level from items in both questionnaires and on the nutrient intake level from items in each questionnaire. 4) And analysing this study data by multiple stepwise regression, we selected twenty seven food items whic could explained over 85% of inter-individual variation of nutrients(energy, carbohydrate, fat, protein, vit A, vit B1, vit B2, vit C, Ca). From above results, we suggested that it is neccessary to standardize questionnaire and perform validity studies.; Summary

A Case-Control Study of Risk Factors for Hemorrhagic Fever with Renal Syndrome in Korean Soldiers.: Jung Han Park, Min Hae Yeh, Yeon Ja Hwang, Kenneth E Dixon; Korean J Epidemiol. 1994;16(1):41-53.

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A case-control study was conducted to identify the specific risk fatctors for hemorrhagic fever with renal syndrome(HFRS) in Korean soldiers. The case group consisted of 196 confirmed HFRS patients who were admitted to the Capital Armed Forces General Hospital between I November 1989 and 15 January 1992 and were 25 years old or younger. The control group consisted of 258 non-HFRS patients who were admitted to the same hospital and meeting following conditions; onset of symptom was within five days before or after the onset date of case, had regular military activities up to the onset of symptom, and no noticeable signs for the diagnosis. Most of the cases and controls came from the units located in Kyonggi province (61.7% of cases, 75.9% of controls) and Kangwon province (31.6% of cases, 15.5% of controls). The distribution of places where the cases and controls had moved into during 60 days period prior to admission was similar to that of the base units. Among 196 cases, 89.3% occurred in October through December and 46.9% in November. Significant risk factor was the field living condition. The odds ratio (OR) for sleeping in a tent vs not sleeping in a tent during 60 days period prior to admission was 1.55 (95% CI=1.07-2.25) and that for sleeping on the bare ground or in a vehicle was 3. 63 (95% CI=1.48-8.86). Other statistically significant risk factors were advanced tac tical training (OR=1.51, 95% CI=1.02-2.24), drinking surface water (OR=1.83, 95% CI=1.21-2.77), exposure to indoor dust (OR=1.58, 95% CI=1.05-2. 37), fixing trench (OR=1.63, 95% CI=1.12-2.37) and having seen Apodemus in the outdoors (OR=4. 61, 95% CI=2.12-10.02). Most of these risk factors were related with camping (field living condition) and thus the interaction between each risk factor and camping was examined by cross tabulation. None of the ORs for five risk factors was statistically significant for the cases who had no camping. However all of the ORs for the cases who had camping were increased and statistically significant ;2.27 for advanced tactical training, 2.64 for drinking surface water, 2.14 for exposure to indoor dust, 2.91 for fixing trench, and 7.58 for having seen Apodemus in outdoors. It was revealed in this study that the highest risk factor for HFRS is camping in the area where the Apodemus inhabits.; Summary

Relationship of Body Fat Distribution and Serum Lipids in Men.: Byung Yeol Chun, Min Hae Yeh, Sung Kook Lee, Yun Kyeong Rho, Soon Yeol Nam; Korean J Epidemiol. 1994;16(1):28-40.

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This study was conducted to investigate the relationship of body fatness indicators and serum lipids (total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein(LDL) cholesterol, triglycerides, myocardial infarction(MI) index) to find anthropometric indicators of body fat distribution that are strongly associated with serum lipids. 347 adult male workers of an industry in Kyungpook province were selected and data on the general characteristics were obtained using questionnaire from June 26 to June 29, 1991. Serum lipids were tested with 5 ml fasting blood and height, weight, circumferences of waist, hip and mid-thigh, five subcutaneous fat thickeness(biceps, triceps, supscapular, suprailiac, thigh) were mea sured using Ultrasound type A TATT. Waist circumference, waist/hip circumference ratio and subcutaneous fat thickness of suprailiac area are significantly increased with increasing age, but thigh circumference is significantly decreased (P< 0.05). These results suggest that central obesity is closely related to age and waist circumference may be the best indicator of body fatness or body fat distribution in men. In younger age group(below 40 year old), the result of canonical correlations analysis suggests that circumferences(0.501) was slightly closely related to serum lipids than subcutaneous fat thickness(0.493), however, in older age group (above 40 year old), subcutaneous fat thickness(0.528) were more strongly associated with serum lipids than circumferences(0.419). Weighted canonical analyses suggest that biceps and suprailiac areas in younger age group and sub scapular area in older age group are stronger indicators of serum lipids among .subcutaneous fatness measurements. Of the circumferences, waist is the most strongest indicator of serum lipids in both age groups. Therefore, it is recommended that circumference of waist and subcutaneous fat thickness of subscapular area should be measured to estimate the degree of central obesity for preventing cardiovascular disease in men.; Summary

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