• Korea journal of population studies
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• v.31 no.1
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• pp.75-97
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• 2008

Recently Korea is expected with the decrease of population in working ages and also population structure, especially age structure, has changed as aging goes faster. This study focuses on the relationship between age structure and wage structure to analyzes the cohort size effect on the change of age-earnings profile. Our empirical analysis based on Wright(1991)'s model takes weighted OLS regression using the male worker's data of Ministry of Labor 'Wage Structure Survey'($1990{\sim}2006$). In pooled data, we take the conclusion that the cohort size effect was found in high school and college graduate workers, but the effect is different between them. The labor market entry effect of high school graduate workers is negative(-) and his persistent effect is positive(+). On the other hand, the cohort size effect of college graduate workers have appeared the opposite directions in contrary with the existing results of Welch(1979) and Wright(1991). This results are seen as the possibility that college graduate worker has the benefit of wage level by his relative cohort size in spite of high unemployment of young graduate. It will be the sign of need that we should interest in the change of age structure with balancing the labor supply side approach and the demand side study which the previous studies was mainly tended to focus on.

• Journal of Preventive Medicine and Public Health
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• v.40 no.2
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• pp.95-101
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• 2007

Focusing on complex diseases of public health significance, strategic issues regarding the on-going Korean Genome Cohort were reviewed: target size and diseases, measurements, study design issues, and follow-up strategy of the cohort. Considering the epidemiologic characteristics of Korean population as well as strengths and drawbacks of current research environment, we tried to tailor the experience of other existing cohorts into proposals for this Korean study. Currently 100,000 individuals have been participating the new Genome Cohort in Korea. Target size of de novo collection is recommended to be set as between 300,000 to 500,000. This target size would allow acceptable power to detect genetic and environmental factors of moderate effect size and possible interactions between them. Family units and/or special subgroups are recommended to parallel main body of adult individuals to increase the overall efficiency of the study. Given that response rate to the conventional re-contact method may not be satisfactory, successful follow-up is the main key to the achievement of the Korean Genome Cohort. Access to the central database such as National Health Insurance data can provide enormous potential for near-complete case detection. Efforts to build consensus amongst scientists from broad fields and stakeholders are crucial to unleash the centralized database as well as to refine the commitment of this national project.

• Journal of Preventive Medicine and Public Health
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• v.43 no.6
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• pp.543-548
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• 2010

Objectives: The objective of this study was to calculate sample size and power in an ongoing cohort, Korea radiation effect and epidemiology cohort (KREEC). Method: Sample size calculation was performed using PASS 2002 based on Cox regression and Poisson regression models. Person-year was calculated by using data from '1993-1997 Total cancer incidence by sex and age, Seoul' and Korean statistical informative service. Results: With the assumption of relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, sample size calculation was 405 events based on a Cox regression model. When the relative risk was assumed to be 1.5 then number of events was 170. Based on a Poisson regression model, relative risk=1.3, exposure:non-exposure=1:2 and power=0.8 rendered 385 events. Relative risk of 1.5 resulted in a total of 157 events. We calculated person-years (PY) with event numbers and cancer incidence rate in the nonexposure group. Based on a Cox regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, 136 245PY was needed to secure the power. In a Poisson regression model, with relative risk=1.3, exposure:non-exposure=1:2 and power=0.8, person-year needed was 129517PY. A total of 1939 cases were identified in KREEC until December 2007. Conclusions: A retrospective power calculation in an ongoing study might be biased by the data. Prospective power calculation should be carried out based on various assumptions prior to the study.

• Journal of Preventive Medicine and Public Health
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• v.48 no.6
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• pp.280-286
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• 2015

Objectives: Approximately 10% to 15% of lung cancer cases occur in never-smokers. Hormonal factors have been suggested to lead to an elevated risk of lung cancer in women. This systematic review (SR) aimed to investigate the association between hormonal replacement therapy (HRT) and the risk of lung cancer in women using cohort studies. Methods: We first obtained previous SR articles on this topic. Based on these studies we made a list of refereed, cited, and related articles using the PubMed and Scopus databases. All cohort studies that evaluated the relative risk of HRT exposure on lung cancer occurrence in women were selected. Estimate of summary effect size (sES) with 95% confidence intervals (CIs) were calculated. Results: A total of 14 cohort studies were finally selected. A random effect model was applied due to heterogeneity (I-squared, 64.3%). The sES of the 14 articles evaluating the impact of HRT exposure on lung cancer occurrence in women indicated no statistically significant increase in lung cancer risk (sES, 0.99; 95% CI, 0.90 to 1.09). Conclusions: These results showed that HRT history had no effect on the risk of lung cancer in women, even though the sES of case-control studies described in previous SR articles indicated that HRT had a protective effect against lung cancer. It is necessary to conduct a pooled analysis of cohort studies.

• Health Policy and Management
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• v.24 no.1
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• pp.35-46
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• 2014

Background: This paper describes the relationship and effect of health examination on personal medical cost by identifying the difference of the cost for medical care in physician visit between the population without and with health examination. Methods: After classifying into three cohorts in which, independent variables were designed according to the Andersen's behavioral model, the association of personal medical cost for medical care and prescription drugs which is dependent variable was analyzed by t-test and Mann-Whitney test for description and gamma regression model for inference. Results: In personal average medical cost, the population with health examination paid significantly more than without health examination, 11.6% more in cohort 2008, 26.6% more in cohort 2009, and 48.0% more in combined cohort. The odds ratio on medical expenditure of outpatients with health examination was 1.067, 1.126, 1.398 significantly in cohort 2008, 2009, and combined cohort respectively, comparing to the group without health examination. In independent variables, that is female, the elderly, never married, non-working, non-metropolitan, the higher family income, the smaller family size, people with disability, the people with chronic disease, and people with health examination have significantly being paid more tendency showing positive association with medical cost. Conclusion: This result showed that medical expenditure in physician visit has been increased after taking a health examination. Therefore reasonable limitation of getting preventive medical service is suggested to avoid medical shopping around and reduce being repeated health examination by unifying control to find out easily the clinical results from various medical facilities.

• Journal of Distribution Science
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• v.16 no.9
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• pp.79-99
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• 2018

Purpose - Food consumption in Korea has changed in paradigm as it has grown qualitatively in the past in quantitative shortages. Consumer food consumption patterns are rapidly changing due to changes in economic, social and population conditions, scientific and technological development, climate change, and market opening. At the same time, there is a need to actively respond to these changes in terms of the food industry, market, and government policy. The purpose of this study is to examine the changes and characteristics of food consumption expenditure of Korean consumers in-depth and depth in order to provide implications for agriculture, food market and policymakers. Research design, data, and methodology - We analyzed various food consumption changes from the 1980s to 2015 through Household Income and Expenditure Survey raw data from MDIS(Microdata Integrated Service) of Statistics Korea. and conducted the age effect, generation effect, and year effect by cohort analysis. We also conducted comparisons with OECD countries on several indicators. Results - Food consumption spending was slow, and there was no significant change in home consumption, while eating out consumption increased about 20 times in 2015 compared to 1980. Income, age, residential area, number of household members showed significant changes in food consumption. According to the cohort analysis, the changes in the food consumption structure are largely due to age effect, and the year, age, and generation effects are different for each food item. Conclusions - Food consumption has a significant impact on not only the nutritional status of consumers but ultimately the public health. Therefore, they should be regarded as a strategic policy area of central government rather than a matter of size and change of food consumption expenditure.

• Journal of the Korean Society of Food Culture
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• v.19 no.1
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• pp.118-127
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• 2004

The purpose of this study was to identify the preferred types and consumption patterns of food away from home by socio-demographic factors including cohort groups, sex. and consumption patterns consisting of 6 types. Data were collected from 412 respondents by questionnaire method in April through May 2002. Regression results indicate that sex, age, family income, family type and size as well as the consumption patterns were significant in explaining the determinants of food away from home expenditures. Four logit function (each for Korean, American, Japanese, and bunsik) results showed that each type of food away from home was likely to vary depending on socio-demographic factors (i.e., cohort groups and sex) and the consumption patterns (i.e., convenience and simple, distinction and variety, tradition oriented, foreign design, health and quality oriented, sensible taste and mood). Similarities and differences in food away from home types are discussed, and future implications for food and nutrition specialists as well as food industrial marketers are provided.

• Communications for Statistical Applications and Methods
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• v.25 no.5
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• pp.545-557
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• 2018

The inclusion of covariates in the model often affects not only the estimates of meaningful variables of interest but also its statistical significance. Such gap between statistical and subject-matter significance is a critical issue in huge sample studies. A popular huge sample study, the sample cohort data from Korean National Health Insurance Service, showed such gap of significance in the inference for the effect of obesity on cause of mortality, requiring careful consideration. In this regard, this paper proposes a sample size calibration method based on a Monte Carlo t (or z)-test approach without Monte Carlo simulation, and also proposes a test procedure for subject-matter significance using this calibration method in order to complement the deflated p-value in the huge sample size. Our calibration method shows no subject-matter significance of the obesity paradox regardless of race, sex, and age groups, unlike traditional statistical suggestions based on p-values.

• Clinical and Experimental Pediatrics
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• v.64 no.9
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• pp.489-493
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• 2021

Background: There is evidence of destructive effects of oxytocin use during labor on neurodevelopment. Purpose: This meta-analysis pooled all observational studies to determine the association between labor induction and the risk of attention-deficit/hyperactivity disorder (ADHD) among children. Methods: All observational studies (case-control and cohort) were reviewed until September 2020 after searches of the PubMed, Scopus, and Web of Science databases, the gray literature, and conference proceedings. The pooled odds ratios (ORs), relative ratios (RRs), and 95% confidence intervals (CI (swere calculated as random effect estimates of association among studies. Results: All observational studies were reviewed, including 4 cohort studies including 2,885,743 participants and 3 case-control studies including 51,135 participants (10,961 with ADHD and 40,174 in control groups) with a sample size of 2,936,878 participants. The pooled estimates of OR and RR did not indicate a significant association between labor induction and ADHD among children (OR, 1.13; 95% CI, 0.90-1.35) and (RR, 1.10; 95% CI, 0.96-1.24). Conclusions: The findings showed that labor induction is not associated with an increased risk of ADHD among children. However, more studies are needed to investigate the relationship between labor induction and ADHD.

• Journal of Preventive Medicine and Public Health
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• v.48 no.5
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• pp.225-230
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• 2015

Objectives: The epidemiological characteristics of breast cancer incidence by age group in Korean women are unique. This systematic review aimed to investigate the association between hormone replacement therapy (HRT) and breast cancer risk in Korean women. Methods: We searched electronic databases such as KoreaMed, KMbase, KISS, and RISS4U as well as PubMed for publications on Korean breast cancer patients. We also conducted manual searching based on references and citations in potential papers. All of the analytically epidemiologic studies that obtained individual data on HRT exposure and breast cancer occurrence in Korean women were selected. We restricted the inclusion of case-control studies to those that included age-matched controls. Estimates of summary odds ratio (SOR) with 95% confidence intervals (CIs) were calculated using random effect models. Results: One cohort and five case-control studies were finally selected. Based on the heterogeneity that existed among the six studies (I-squared=70.2%), a random effect model was applied. The summary effect size of HRT history from the six articles indicated no statistical significance in breast cancer risk (SOR, 0.983; 95% CI, 0.620 to 1.556). Conclusions: These facts support no significant effect of HRT history in the risk of breast cancer in Korean women. It is necessary to conduct a pooled analysis.