• Management Science and Financial Engineering
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• v.16 no.3
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• pp.49-70
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• 2010

Customer population management models can be classified into three categories: the first category includes the models that analyze the customer population at cohort level; the second one deals with the customer population at aggregate level; the third one has interest in the interactions among the customer populations in the competitive market. Our study proposes a model that can analyze the dynamics of customer population in consumer-durables market at aggregate level. The dynamics of customer population includes the retention curves from the purchase or at a specific duration time, the duration time expectancy at a specific duration time, and customer population growth or decline including net replacement rate, intrinsic rate of increase, and the generation time of customer population. For this study, we adopt mathematical ecology models, redefine them, and restructure interdisciplinary models to analyze the dynamics of customer population at aggregate level. We use the data of previous research on dynamic customer population management at cohort level to compare its results with those of ours and to demonstrate the useful analytical effects which the precious research cannot provide for marketers.

• Korean Journal of Child Studies
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• v.30 no.4
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• pp.69-85
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• 2009

The purpose of this study was to identify developmental trajectories of externalizing problems in preschoolers and to investigate dimensions of temperament and parental behaviors associated with trajectory groups. Subjects were 180 3- to 5-year-old preschoolers (96 males, 84 females) in the metropolitan area of Seoul. They were assessed three times at 5 month intervals over a one year period. Teachers reported on children's behavior problems, and parents reported on children's temperaments. Latent Growth Curve Modeling Analysis with cohort sequential design revealed externalizing behaviors gradually decreased between 3 and 6. At the 6-year-old level externalizing behaviors were associated with high novelty seeking temperament. The results were discussed in terms of the importance of longitudinal research in developmental psychopathology.

• Journal of Environmental Health Sciences
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• v.34 no.1
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• pp.1-11
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• 2008

The purpose of this study was to investigate air quality in Chungju, Korea, using data obtained with a local air quality monitoring system. We have utilised cohort studies to investigate the relations between environmental pollution and the health of residents near large industrial complexes since 2004. This study analyzes the $O_3,\;NO_2,\;SO_2,\;CO\;and\;PM_{10}$ concentration in Chungju from 2002 to 2006. Air pollutants are closely related to the number of manufacturing facilities and cars, energy utilization and weather conditions. Generally, the diurnal concentration of air pollutants in Chungju reached the highest level in the morning (about$08:00{\sim}$) and early evening (about$19:00{\sim}$). On the other hand, the diurnal concentration of ozone as recorded gives the highest amount in late afternoon (about$16:00{\sim}$) and lowest in early morning (about$08:00{\sim}$). The concentration of air pollutants in Chungju was highest from winter to spring and lowest during the summer season. On the other hand, the monthly variation of ozone concentration was greatest in June and smallest in December. Also the, $PM_{10}$ concentration posted the highest record in April and the lowest during September. In general, this study analyzed air pollution changes in Chungju as well as in large scale industrial complex regions within Korea such as Ulsan, Pohang, Kwangyang, Sihwa Panwol and Gangneung in Korea. We compared the air quality of Chungju with those of these cites and found that air pollutants except for CO in Chungju was generally lower than large industrial complex regions.

• Clinical and Experimental Pediatrics
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• v.64 no.3
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• pp.130-135
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• 2021

Background: The clinical significance of lip-tie, or a tethered maxillary frenulum, remains under debate. Clinicians and parents are often perplexed when deciding whether procedures available to relieve a seemingly tight or severe maxillary frenulum are needed. Purpose: No previous studies have assessed the consequences of not subjecting a tethered maxillary frenulum in newborns to surgical intervention. This study aimed to contribute the first prospective trial on this topic with a relatively extended follow-up of these newborn infants. Methods: This prospective observational questionnaire-based cohort trial was performed in a community setting and aimed to determine whether lip-tie is associated with an increased likelihood of eventual feeding or oral disorders. Results: The convenience sample comprised of 61 consecutively arriving infants with concomitant tethered frenula who were treated at the clinic for various reasons. This cohort was compared with a random sample of 66 age-matched children for a mean follow-up period of 6.42 years. Infants undergoing oropharyngeal procedures were excluded. Awareness of a deviation in oral structures was reported by 18% of the study group versus 0% of the controls. Mothers participating in the study group (24.6%) less frequently recalled painful nipples or discomfort during breastfeeding than those in the control group (47.0%) (P<0.01). There were no intergroup differences in other types of feeding difficulty, dental hygiene, pronunciation, or speech development. Conclusion: Our findings suggest that a tethered labial frenulum is not associated with an increase in breastfeeding disturbances or oral disorders. These data encourage clinicians to question the need to intervene in cases of tethered maxillary frenula.

• Journal of Sasang Constitutional Medicine
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• v.32 no.4
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• pp.86-95
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• 2020

Objectives Meal and nutrition are important lifestyle factors that affect maintenance and promotion of health status and are also associated with chronic diseases. In Sasang constitutional medicine, dietary behavior according to the characteristics of Sasang constitution (SC) types is a key component in health management. The aim of this study was to evaluate the nutritional status and quality of meals according to the SC. Methods This was a cross-sectional study of 1,947 subjects surveyed in a community-based cohort called the Korean Medicine Daejeon Citizen Cohort study. Data were collected including demographic characteristics, Korea Sasang Constitutional Diagnostic Questionnaire, and nutrition quotient (NQ) for adults. We analyzed the differences in NQ grade and scores among three SC types: Taeeumin (TE), Soeumin (SE), and Soyangin (SY), by conducting chi-square and ANCOVA tests. Results The distribution of SC into TE, SE, and SY types was 43.1%, 25.2%, and 31.8%, respectively. The mean NQ score of all subjects was 53.4±8.6. There was a significant difference in the distribution of NQ grades and mean of NQ scores among SC types, including total and four sub-factors: balance, diversity, moderation, and dietary behavior. The TE type had the lowest score for the moderation factors in the crude model. The SE type showed lower NQ scores than the TE and SY types in all domains except moderation after adjusting for variables. Conclusions We found that dietary behaviors had to be distinct according to the SC types. These results elucidate why it is important to develop a customized dietary habit management program considering the SC types.

• Journal of Sasang Constitutional Medicine
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• v.34 no.4
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• pp.27-37
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• 2022

Objectives The purpose of this study is to propose a method to more specifically identify Sasang constitutional risk factors of metabolic syndromes by adjusting the cut-off value of Korea Sasang Constitutional Diagnostic Questionnaire (KS-15). Methods Data of 1997 participants in Korean medicine Daejeon Citizen Cohort study (KDCC) were analyzed. Metabolic syndrome was defined according to the NCEP-ATP III, lifestyle information, and hematologic information including KS-15 and demographic characteristics were used as covariates. Results The 179 subjects with metabolic syndrome accounted for 9.0% of the total. As a result of determining the Sasang constitution for the KS-15 response based on the cut-off values (approximate 0.33), 0.5, and 0.6 of the constitutional score, when performed at the 0.6 cut-off model, the odds ratio of TE was 2.46 which showed a statistically significantly higher risk than the borderline group. For the accuracy of the model and the Area under the curve (AUC), the model accuracy based on the original cut-off of the KS-15 was 0.902 and AUC was 0.737. The accuracy of the model with cut-off of 0.5 and with of 0.6 were 0.904 and 0.902, respectively, and the AUCs were 0.687 and 0.741, respectively. Conclusion In this study, we confirmed that it is effective to increase the cut-off value of KS-15 to 0.6 in the metabolic syndrome risk model. It is expected that this could increase the accuracy of identifying high-risk groups for metabolic syndrome.

• Journal of Preventive Medicine and Public Health
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• v.57 no.1
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• pp.55-64
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• 2024

Objectives: This study investigated the prevalence and characteristics of comorbid conditions in patients exposed to ionizing radiation and those who were involved in the Soviet-Afghan war. Methods: This study analyzed the frequency and spectrum of morbidity and comorbidity in patients over a long-term period (30-35 years) following exposure to ionizing radiation at the Semipalatinsk nuclear test site or the Chornobyl nuclear power plant, and among participants of the Soviet-Afghan war. A cohort study, both prospective and retrospective, was conducted on 675 patients who underwent comprehensive examinations. Results: Numerical data were analyzed using the Statistica 6 program. The results are presented as the mean±standard deviation, median, and interquartile range (25-75th percentiles). The statistical significance of between-group differences was assessed using the Student t-test and Pearson chi-square test. A p-value of less than 0.05 was considered statistically significant. We found a high prevalence of cardiovascular diseases, including hypertension (55.0%) and cardiac ischemia (32.9%); these rates exceeded the average for this age group in the general population. Conclusions: The cumulative impact of causal occupational, environmental, and ultra-high stress factors in the combat zone in participants of the Soviet-Afghan war, along with common conventional factors, contributed to the formation of a specific comorbidity structure. This necessitates a rational approach to identifying early predictors of cardiovascular events and central nervous system disorders, as well as pathognomonic clinical symptoms in this patient cohort. It also underscores the importance of selecting suitable methods and strategies for implementing treatment and prevention measures.

• Safety and Health at Work
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• v.15 no.2
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• pp.208-212
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• 2024

Background: Traffic accidents involving professional drivers have serious societal repercussions. Unique occupational stressors and health risks exacerbate the likelihood of traffic accidents among professional drivers. This study explores the association between presenteeism-impaired work performance due to working while unwell-and traffic accident risk among professional taxi drivers in Japan. Methods: A prospective cohort study was conducted from June 2022 to February 2023, involving taxi drivers from a single company in Fukuoka Prefecture, Japan. Presenteeism was assessed using the Work Functioning Impairment Scale (WFun). Primary outcome involved the number of self-reported minor traffic accidents. The incidence rate ratio (IRR) of minor traffic accident occurrences was estimated using a Poisson regression analysis, adjusted for confounders including sex, age, and driving experience. Results: Of 838 targeted drivers, 435 were included in the analysis. Higher baseline work functioning impairment was associated with a significant trend of increasing IRR of minor traffic accidents (p for trend = 0.045). A dose-response relationship was seen between the degree of presenteeism and incidence rate of minor traffic accidents. Conclusion: Higher levels of presenteeism were associated with an increased risk of traffic accidents among taxi drivers. The findings underscore the need for socio-economic support and prioritized health management to mitigate traffic accident risk among professional drivers. This study highlights the importance of managing non-critical health issues alongside serious health conditions for safer driving practices among professional drivers in Japan.

• Proceedings of the KSCN Conference
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• 2003.11a
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• pp.1010-1020
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• 2003

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.10
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• pp.4681-4688
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• 2016

Objective: Our aim was to estimate whether diabetes mellitus (DM) may be associated with an increased risk of colorectal cancer (CRC) mortality in Japan. Methods: The Japan Collaborative Cohort (JACC) Study is a nationwide prospective study, initiated in 1988, which involves 110,585 subjects (age range: from 40 to 79 years; 46,395 males and 64,190 females). Our present analysis population comprised 96,081 (40,510 men and 55,571 women) who provided details on DM history. The questionnaire also included age, sex, weight, height, family history of CRC, smoking, drinking and exercise habits, and education. Cox proportional-hazard regression was used to estimate the hazard ratio (HR). We used SPSS 21 software to analyze all data. Results: Among the participants with DM, we followed up for 71,174 person-years and 640. deaths from CRC were confirmed; and, among the non-diabetic participants, 785 CRC deaths were identified during 1,499,324 person-years. After adjusting for multivariate confounding factors, such as age, sex, body mass index (BMI), family history of colorectal cancer, smoking habit, drinking habit, physical activity (sports and walking) and education, DM was associated with an increased risk of CRC death (HR 1.4, 95% confidence interval [CI] 1.0-2.0). Diabetic women, but not diabetic men, experienced increased mortality from CRC (HR 1.7, 95% CI 1.0-3.0). Conclusion: The risk of CRC mortality is significantly increased in both sexes and women with diabetes, but no significant increase was seen for diabetic men among Japanese.