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Population-adjusted Mean Age at Incidence (PAMA) for Comparing Incidence Patterns with Age in Different Populations.
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Yoon Ok Ahn, Moo Song Lee, Weechang Kang, Chung Min Lee, Youngjo Lee
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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.
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Methodologic Considerations on the Cohort Study of Risk Factors of Stomach Cancer: On the Incompleteness of Case Ascertainment.
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Moo Song Lee, Wee Chang Kang, Dong Hyun Kim, Jong Myun Bae, Myung Hee Shin, Young Jo Lee, Yoon Ok Ahn
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Korean J Epidemiol. 1997;19(2):152-160.
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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.
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Validation of a Semi-Quantitative Food Frequency Questionnaire.
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Young Sik Kim, Eun Soo Shin, Hye Soon Park, Moo Song Lee
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Korean J Epidemiol. 1995;17(2):249-256.
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The relationships between diet and the occurence of the major diseases of our civilization are of both epidemiological and practical importance to public health problems. Diseases associated with dietary factors rank among the leading causes of illness and death in Korea. Not only for assessment for clinical evaluation, but also for epidemiological concern, we need for rapid and inexpensive methods to assess dietary intake in relating nutrition to health. The validity of a self-administered semi-quantitative food frequency questionnaire was evaluated for a group of 103 men and women aged 26 to 65. Intakes of 8 nutrients computed from the questionnaire were compared with those derived from 3-months diet record. The questionnaire estimates of mean nutrient intake were within about 10% of the mean diet record measurements for nutrients evaluated but iron and vitamin A. The correlation coefficients comparing unadjusted nutrient intakes measured by two methods ranged from 0.27(iron) to 0.57(fat). The correlation coefficients comparing nutrient intakes measured by two methods adjusted for age and sex ranged from 0.26(iron) to 0.50(calories). After adjusted for age and sex or caloric intake, the intakes in iron did not show correlation measured by two methods. A simple and relatively inexpensive questionnaire could be useful information on dietary intake for macronutrients. The modification and revision would be required for assessments of intakes in micronutrients.
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A stochastic analysis on the force of infection by hepatitis B virus in Korea.
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Keun Young Yoo, Moo Song Lee, Youngjo Lee, Bo Youl Choi, Heon Kim, Yong Sik Kim
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Korean J Epidemiol. 1992;14(2):128-137.
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Hepatitis B virus infection is still one of the major health problems in Korea, because of its high prevalence and its deleterious sequellae to liver cirrhosis and hepatocellular carcinoma. However, little is known about incidence (force of infection) of the viral infection. Investigation on the natural history of the virus, such as age-dependency of occurrence, is thus necessary to establish the efficient measures of prevention and management. This study was done to estimate the incidence of hepatitis B virus infection, as well as to assess the prevalent age group of the infection through a stochastic analysis using mathematical models. Data on positivity of hep¬atitis B virus markers (HBsAg, anti-HBs，anti-HBc) were obtained from two different population； a typical rural population in Kyunggi province (n=741) and a health insurance beneficiaries in the Seoul City (n=726). As results, force of infection by the virus was decreasing until the age group around 20, and afterwards remained stationary. The annual incidence of the infection was 15 per 100 persons at birth, 5 per 100 persons at the age, of 10, and about 3 per 100 persons after the age of 20. Proportion of antigen positivity among persons infected by the virus was also decreasing with age increasing. These results suggest that new infection of hepatitis B virus mostly occurs early in life in Korea, resulting in subsequent high prevalence of the infection.
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