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Yoon Ok Ahn 17 Articles
The Association of Reproductive and Menstrual Factors and Colon and Rectal Cancer Risk in Korean Women.
Bong Wha Lee, Dong Hyun Kim, Hunjae Lee, Dae Yong Whang, Yoon Ok Ahn
Korean J Epidemiol. 2002;24(1):76-82.
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Abstract
Recently, there were several epidemiological studies demonstrating that reproductive and menstrual factors are associated with the risk of colorectal cancer in women. A hospital-based case-control study has been conducted to investigate whether the histories of childbearing, menstruation, and breast-feeding are associated with colorectal cancer risk. The cases were consecutively diagnosed, histologically confirmed, incident patients with cancers of the colon and rectum aged 30-79 who were admitted to three tertiary hospitals in Seoul, Korea between March 1995 and August 1997. Controls were selected in the same hospitals as the cases during the same periods. Finally, a total of 151 cases and 110 controls were selected and interviewed on their reproductive and menstrual characteristics using a structured questionnaire. Earlier age at first birth appears to be related with increased risk of colorectal cancer (multivariate relative risk[RR] of colorectal cancer for <21 vs 25 > or = 2.33; 95% confidence interval[CI] 1.1-5.1, p for trend 0.03). Compared with women who experienced menarche at age 16 or older, women whose menarche occurred at age 14 or less appeared at significantly higher risk of rectal cancer(multivariate RR of colorectal cancer for < or = 14 vs > or =16 = 2.26; 95% CI 1.0-3.4, p for trend 0.03). We found no associations for parity, incomplete pregnancies, menopause, use of oral contraceptives, and hormone replacement therapy. These findings suggest that events of reproductive life may have a bearing on female subsequent risk of colon and rectal cancer
Summary
Methods for Estimation of Nationwide Cancer Incidence from Population-based Cancer Registries .
Jong Myon Bae, Choong Won Lee, Duk Hee Lee, Yoon Ok Ahn
Korean J Epidemiol. 2002;24(1):1-6.
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Abstract
While there has not been a nationwide cancer incidence data yet, it is necessary to consider a preferable method for estimation of nationwide cancer incidence under the cancer registry system in Korea. Some papers and texts related to estimate a nationwide cancer incidence were searched and reviewed. It could be summarized into 5 major methods: (1) for having only mortality data for all cancers, (2) of using major demographic factors, (3) of using nationwide mortality data, (4) of using nationwide mortality and survival data, and (5) of considering cancer risk factors. Among the methods, second method of using major demographic factors would be preferable in Korean situation
Summary
The Menstrual, Reproductive, and Lactational Factors and the Risk of Breast Cancer in Korea: A Population Based Case-Control Study.
Myung Hee Shin, Jung Hyun Yang, Kuk Jin Choi, Yoon Ok Ahn
Korean J Epidemiol. 2000;22(1):68-68.
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Abstract
This study was conducted to assess the risk of breast cancer by menstrual, reproductive, and lactational factors in Korean women. A total of 210 women living in Seoul aged 30 to 60 with a first diagnosis of breast cancer from 2 teaching hospitals in Seoul, and 249 control subjects, randomly selected from the female pensioners of Korean Medical Insurance Company living in Seoul were interviewed. There was a increasing risk with the decrease of age at menarche, and the adjusted odds ratio(OR) of early menarche(age 14 years or less compared with over 17 years) was 1.61(95% Confidence Interval [CI]: 0.95-2.74). The longer the interval between menarche and regular menstruation, the less risk of breast cancer(OR=0.31, 95% CI: 0.16-0.60). The effect of these menarche factors were more prominent among premenopausal women. The adjusted OR for the second category(25-29 years old) of the age at first pregnancy and the age at the first full term pregnancy, compared to the reference category( 24 years old), were 0.52(95% CI: 0.30-0.92) and 0.58(95% CI: 0.32-1.06), respectively. The late age at the last full term pregnancy had significant protective effect (OR=0.29, 95% CI: 0.10-0.88), and the age itself was important rather than the interval between the first and last full term pregnancy. Factors related to breast feeding(BF) had protective effect consistently. Among parous women, in referent to no BF, women with 1 year of BF had adjusted OR of 0.34(95% CI: 0.17-0.68), while those with 1-3 years of BF had 0.35(95% CI: 0.18-0.67), 3-5 years had 0.29(95% CI: 0.12-0.74), and more than 5 years had 0.06(95% CI: 0.02-0.17). Age at menarche with regular cycle have stronger effect on especially pre-menopausal breast cancer among Korean women. Recent increase in breast cancer incidence in Korea would be explained by delayed age at first pregnancy or delivery, earlier age at menarche and last delivery, and decrease in brest feeding.
Summary
Population-adjusted Mean Age at Incidence (PAMA) for Comparing Incidence Patterns with Age in Different Populations.
Yoon Ok Ahn, Moo Song Lee, Weechang Kang, Chung Min Lee, Youngjo Lee
Korean J Epidemiol. 1999;21(1):31-35.
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Abstract
Standardized incidence rates have been widely used for comparing incidence patterns between populations, adjusting for differences in demographic structure. These rates can compare overall incidence levels, but to fully understand incidence patterns, an index which links incidence with age is also needed. The authors proposed a statistical method for estimating population-adjusted mean age of incidence (PAMA), based on Poisson distribution and Fieller's theorem. The index was applied with several modifications to data relating to the incidence of breast cancer among Caucasian women living in Los Angeles.
Summary
Measurement Errors on Normotensive Subjects in Screening Test.
Jong Myon Bae, Dae Sung Kim, Jaiyong Kim, Yoon Ok Ahn
Korean J Epidemiol. 1999;21(1):1-7.
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Abstract
BACKGROUND
Blood pressure measurements with a mercury sphygmomanometer serve as the screening test to establish the clinical diagnosis of primary hypertension. But one of the problems of hypertension screening is the variability of blood pressure measurements.
METHODS
In order to identify the measurement error of blood pressure through the biennial health screening program of Korea Insurance Medical Corporation, we compared the blood pressure of screening test with true value which defined as the mean of blood pressures taken from the direct contact and twice check-up among normotensive Seoul Cohort participants.
RESULTS
Three hundred forty-nine participants had both data of screening measurement and survey of direct contact. The means of difference in systolic and diastolic blood pressure between both data were 8.47 mmHg and 6.54 mmHg, respectively. These results showed statistical significance with paired t-test (p=0.001).
CONCLUSION
Our findings indicated that screening measurement of blood pressure had false negative. And if a epidemiologic study about blood pressure used the data of screening test, it should adjust value of systolic and diastolic blood pressure with adding 8 and 7 mmHg, respectively.
Summary
Methodologic Considerations on the Cohort Study of Risk Factors of Stomach Cancer: On the Incompleteness of Case Ascertainment.
Moo Song Lee, Wee Chang Kang, Dong Hyun Kim, Jong Myun Bae, Myung Hee Shin, Young Jo Lee, Yoon Ok Ahn
Korean J Epidemiol. 1997;19(2):152-160.
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Abstract
BACKGROUND
AND PURPOSE: The authors conducted the study to evaluate the incompleteness of follow-up as well as the validity of the diagnostic code in the medical insurance databases in a cohort study. They also suggested several useful regression models for the analysis of such incomplete data.
METHODS
The subjects of Seoul Cohort(n=14,533) were followed up for three and a half years. Based on the chart reviews of the subjects who had the diagnostic code of gastric cancer in the medical insurance databases, forty-four cases of gastric cancer were idenfified, using cancer registry databases and death certificates as the secondary source. Regression coefficients and the associated p-values were estimated using the following six methods and the results were compared with each other. Method 1: The subjects with the diagnostic code in the medical insurance databases were considered as the cases of gastric cancer.
Method
2: The confirmed cases were considered as the cases of gastric cancer. Method 3: The cases were the subjects with the diagnositc code whose diagnosis was confirmed by medical chart reriew. Method 4: Ordinal logistic regression.
Method
5: Weighted logistic regression. Method 6: Polytomous logistic regression RESULTS: A total of 12,541 subjects were followed up excluding censored cases. One hundred and nine subjects were diagnosed with gastric cancer in the medical utilization databases: forty-three were probable cases whose dianosis was not confrimed by chart review, twenty-six were ruled out and 26 were confirmed cases. Another 14 cases were confirmed using the cancer registry and death certificates. Using the secondary sources, four another cases were confirmed and 44 cases were confirmed during follow-up. In method 1, past history of gastritis and gastric ulcer was significant risk factor whereas intake frequency of fresh vegetable, ice cream and coffee was associated with significantly decreased risk. In the second and the sixth method, green tea was a significant protective factor, whereas in methods 3-5, no significant variables were found.
CONCLUSIONS
Polytomous logistic regression was the preferred method in the cohort study using secondary sources of information for the follow-up, and it provided additional information for the risk factor identification, especially for the specificity of the risk factors.
Summary
Usefulness of Somatotype Drawing as a Instrument of Measuring Obesity Level in Korea.
Jong Myon Bae, Yoon Ok Ahn
Korean J Epidemiol. 1996;18(1):101-107.
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Abstract
BACKGROUND
As modern epidemiologic studies began to identify obesity as a risk factor for cardiovascular disease, diabetes, hypertension, and cancer, measuring the degree of excess body fat is important on epidemiologic surveys. The evaluation of obesity level in epidemiologic surveys has been mostly done indirectly by measuring patient's height and weight. But, the anthropometry could not be done to respondents of recalling past anthropometric values or to proxy respondents. This study was attempted to elucidate usefulness of a somatotype drawing as a measuring instrument of obesity level in epidemiologic surveys in Korea.
METHOD
The inclusion criteria of subjects were (1) members of the Seoul Cohort Study, who were recruited by self-administered structured questionnaire survey through mailing to the healthy men between the ages of 40 and 59 years through the program of a biennial health checkup offered by the Korean Medical Insurance Corporation (KMIC), and (2) volunteers for cancer screening program offered by KMIC. For assessing usefulness of the instrument, measurement of status/weight and self-administered questionnaire survey were done separately through the program of a biennial health checkup and of cancer screening.
RESULTS
The data were collected from 138 subjects, whose Body Mass Index (kg/M2) was 23.58+/-1.46 (mean+/-SD). When the validity was measured through correlation with BMI, Spearman's correlation coefficient (rs) was 0.72 (p<0.05), that remained statistically significant after adjusting age, education level, and monthly income and occupation. And, the grades of somatotypo drawing were grouped as 1-3, 4-6, 7-8 by ANOVA and Tukey test.
CONCLUSIONS
Instrument using somatotype drawing is applicable to screen degree of body fat in self-administered questionnaire surveys in Korea.
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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Abstract
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
Research methodology in medical studies
Yoon Ok Ahn, Hyung-gi Lee
Korean J Epidemiol. 1990;12(2):107-114.
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Abstract
Research methodology in medical studies has seldom been touched upon in Korea. The curricula on research methodology in the postgraduate or residential training courses have been adopted by few medical schools/societies for medical science. So, actually most of the medical researchers in Korea have learned about study nethodology by themselves through doing researches. In this paper, the authors emphasize the important role of methodology itself in science advancement. The development and evolution in philosophical thinking about scientific methods e.g. deduction, induction, falsificationism, post-positivism, and activity theory were reviewed. Methodological issues in medical science must be more important and subtle than in other sciences, because the primary material of medical researches is the living human. Biostatistical techniques and probability theories should be some essential parts of the pillars in medicine. The authors suggest that Korean societies for medical science should pay attention to the research methodology itself, and have more frequent and active arguementations on research methodology which is an indispensable activities in science.
Summary
Cohort study on the asymptomatic chronic carrier rate of hepatitis B virus among male adults in Korea
Byung Joo Park, Yoon Ok Ahn
Korean J Epidemiol. 1989;11(2):263-273.
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Abstract
In Korea, the rates of hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC) incidence, a major risk factor for which is HBV infection, are among the highest in the world. Therefore, in order to establish strategies for the prevention of HBV infection and HCC, the natural history of HBV infection should be urgently investigated; in particular, it is important to estimate the rate of asymptomatic chronic HBV infections, because individuals with such infections are considered at risk of chronic liver diseases such as HCC. In order to identify the prevalence of chronic HBV infections among adult males, 1495 individuals without any abnormal findings during their regular physical checkup in 1986 were randomly selected from the population insured by the Korea Medical Insurance Corporation. Radioimmunoassay (RIA) tests were performed on the subjects to detect the serological markers of HBV; namely, hepatitis B surface antigen (HBsAg), antibody to the hepatitis B surface antigen (anti-HBs) and antibody to the hepatitis B core antigen (anti-HBc), and direct interviews were conducted to determine participants’ history of hepatitis B vaccination. Of these subjects, 624 healthy males who were found to be nonvaccinees were selected and followed up for 2 years. In 1988, re-tests of the three serological markers of the hepatitis B virus using RIA testing, as well as physical checkups including liver function tests, were performed. The final study population of 370 adult males consisted of those who had no abnormal findings in either physical checkups, had not been vaccinated against HBV, and received a re-test of the serological markers of HBV after the follow-up period. The point prevalence rate of HBsAg among the 370 men enrolled was 9.6% (95% confidence interval [CI]=6.6-12.6), and after the 2-year follow-up period, the rate increased to a significantly higher level (13.0%; 95% CI=9.6-16.6). The rate of asymptomatic chronic carriers whose HBsAg tests continued to be positive during the 2-year follow-up period was 6.2% (95% CI=3.7-8.7), corresponding to 60% of the point prevalence at the time of enrollment. The age-adjusted chronic carrier rate calculated using males 20-59 years of age from the 1985 Nationwide Population and Housing Census data as a standard population was 6.2%(95% CI=6.19-6.21). The asymptomatic chronic carrier rates by age group were 6.8%in their 20s and 30s, 5.6%in their 40s, and 4.3%in their 50s; a decreasing trend according to age was found, but it was not statistically significant. The number of asymptomatic chronic carriers in Korea as of 1985 was estimated to be around 1.3 million men between their 20s and 50s. The serological profiles of the HBV markers suggested frequent loss and acquisition of the serological markers during the 2 years. While the prevalence of susceptible decreased from 14.1% at the time of enrollment to 12.7% at the end of the 2-year follow-up, the prevalence of HBsAg increased significantly. Thus, studies more precisely elucidating the mechanisms underlying these patterns in serological profiles are needed
Summary
Design principles of clinical trials
Yoon Ok Ahn
Korean J Epidemiol. 1989;11(1):1-17.
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Abstract
Summary
Distribution of the serologic markers of hepatitis B virus after the hepatitis B vaccination on healthy Korean adults
Yoon Ok Ahn, Keun Yong Yoo, Byung Joo Park, Yong Ik Kim, Chung Yong Kim, Tae Soo Park
Korean J Epidemiol. 1987;9(1):28-39.
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Abstract
Summary
Epidemiologic characteristics of AIDS
Yoon Ok Ahn
Korean J Epidemiol. 1985;7(2):158-167.
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Abstract
Summary
Panel discussion : AIDS control
Il Soon Kim, Yong Ik Kim, Joung Soon Kim, Taik Sung Nam, Hak Kyun Shin, Yoon Ok Ahn, Won Ha Yoo, Won Young Lee, Jung Bock Lee
Korean J Epidemiol. 1985;7(2):187-191.
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Abstract
Summary
Analysis of selection bias in a case-control study
Yoon Ok Ahn
Korean J Epidemiol. 1985;7(2):195-201.
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Abstract
Several situations in case-control studies, such as using hospital controls, prevalent cases, special surveillance groups, and low participation rate, necessitate evaluation of selection biases. A case-control study of renal adenocarcinoma which has been conducted in 100 towns around Boston, U.S.A., showed low participation (interviewed) rate, 41.1% and 62.0% among cases and controls, respectively. By comparing medial abstract data of interviewed and not-interviewed cases, interviewed data of controls and mail-questionaire data of not-interviewed controls, it was possible to estimate selection odds ratio for selected 8 variables and to assess selection bias associated with smoking, obesity, renal caluli, and hypertension. The conclusions drawn were as follows; 1) It is certain that a considerable number of factors served as actual selection factors in case-control study. 2) The interpretability of certain association resulted from interviewed data was strengthened and weakened by analysis of selection bias. For the valid explanation of study results of interviewed data, the evaluation of selection bias should be quite valuable and necessary. 3) The simplified schematic presentation of theoretical aspects of selection bias can be useful to analyse it afterward, while, there are no standardized methods of data collection for the evaluation of selection bias.
Summary
A review study on descriptive epidemiology of HBs-Antigen in Korea
Yoon Ok Ahn
Korean J Epidemiol. 1982;4(1):35-45.
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Abstract
Summary
An epidemiologic survey on cancer epidemic at pukcheju-gun.
Yoon Ok Ahn, Byung Joo Park, Jong Myon Bae, Duk Hyung Lee, Dong Jin Kim, Jun Hwan Kim, Jong Won Kang, Yong Jin Jung, Dong Mo Rhie
Korean J Epidemiol. ;15(2):185-195.
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Abstract
According to a newspaper account for the epidemic occurrence of cancer patients at an area of Pukcheju-gun, epidemic survey was conducted to identify the epidemicity and possible cause of the cancer epidemic from Sep. 23, 1993 to Sep. 28, 1993. Housefold survey for identifying prevalent There was no female cancer cases, no temporal dusting pattern of cancer occurrence and no clustering of specific types of cancer. In the evaluation of ground water and sea water, carcinogenic substances were not detected. According to the above evidences, it was difficult to confirm that there was an epidemic occurrence of cancer at the area. And the possibility of the association of environmental carcinogenic factors with the cancer occurrence seemed to be very low.
Summary

Epidemiol Health : Epidemiology and Health