• 대한예방의학회:학술대회논문집
• /
• 1994.02a
• /
• pp.417-425
• /
• 1994

Although animal studies have been used most often for quantitative risk assessment, it is generally recognized that well-conducted epidemiologic studies would provide the best basis for estimating human risk. However, there are several features related to the design and analysis of epidemiologic studies that frequently limit their usefulness for quantitating risks. The lack of accurate information on exposure in epidemiologic studies is perhaps the most frequently cited limitation of these studies for risk assessment. However. other features of epidemiologic study design, such as statistical power, length of follow-up, confounding, and effect modification, may also limit the inferences that can be drawn from these studies. Furthermore, even when the aforementioned limitations are overcome, substantial uncertainty exists concerning the choice of an appropriate statistical (or biologic) model for extrapolation beyond the range of exposures observed in a particular study. This paper focuses on presenting a review and discussion of the methodologic issues involved in using epidemiologic studies for risk assessment. This review concentrates on the use of retrospective, cohort, mortality studies of occupational groups for assessing cancer risk because this is the most common application of epidemiologic data for quantitative risk assessment (QRA). Epidemiologic data should not be viewed as a panacea for the problems inherent in using animal bioassay data for QRA. Rather, information that can be derived from epidemiologic and toxicologic studies complement one another, and both data sources need to be used to provide the best characterization of human risk.

• The Korean Journal of Malacology
• /
• v.13 no.2
• /
• pp.193-201
• /
• 1997

1990년 3월부터 1991년 2월까지 전라북도 군산 연안에 서식하는 동죽을 채집하여, 순간성장율, 순간사망율, 평균 생체량, 연간 생물생산력에 대하여 조사하였다. 치패는 각장 약 0.75 mm가 7월에 처음 채집되었으며, 0-5세의 6개 cohort로 구분되었다. 순간성장률은 여름철에 ？고 겨울철에 낮았지만, 순간사망률은 여름철에 높았다. 조사지역에서 동쪽 개체군의 연간평균 생체량은 3.865 g/$m^2$이었으며, 연간생산량은 3.933 g/$m^2$이었고, 연간 회전율은 1.020, 회전시간은 0.986년으로 추정되었다.

• Journal of Digestive Cancer Reports
• /
• v.8 no.2
• /
• pp.97-101
• /
• 2020

Metformin is a widely used first-line anti-diabetic drug worldwide. Epidemiologic studies using the large population-based cohort database have shown the association between metformin uses and reduced risk of various type cancers including gastric cancer. In the gastric cancer prevention, metformin use was associated with the significant reduction of gastric cancer risk, especially for long-term metformin users. However, there is no well-designed randomized controlled clinical trial investigating the effect of metformin as a chemopreventive drug for gastric cancer. Therefore, further well-designed clinical trials will be needed to implement metformin for chemoprevention of gastric cancer.

• Journal of Korean Medical classics
• /
• v.23 no.4
• /
• pp.63-102
• /
• 2010

Purpose : To propose various types of clinical research which is feasible for botanical new drug (IND) development processes, and suggest essential steps to development of study protocol for IND. Methods : Literature-based discussions and one research group's experience is given regarding domestic act, regulation, and system. Results : In order to get an approval of IND for botanical drug in Korea there are several types of clinical research to conduct. In quality control steps for standardized medicinal herbs, case reports or case series can be conducted, and for good manufacturing practice(GMP) steps, we can conduct case reports, case series, and retrospective cohort studies. In addition, as long as we gathered good laboratory practice(GLP) data we can conduct up to quasi-experimental studies and clinical trials including investigator initiated trials. In order to conduct these studies development of study protocol is essential. First, we obtain historical evidence including target disease and indication, efficacy, safety, and endpoints by reviewing medical classics. Second, we obtain clinically and statistically important data by conducting non-clinical studies, observation studies, and quasi-experimental studies. Third, we generate research hypotheses and purposes and explore methodologies, endpoints, clinical practice guidelines, cost-effectiveness, and commercial potential. Finally, we develop study protocol with aid of biostatistician or expert in contract research organization. Discussions and conclusions : This study have obvious limitations in that most thoughts, suggestions, and proposes are from one research group's experience. Therefore, we hope to see various types of research in this topic and process from other research group as well.

• Korean Journal of Biological Psychiatry
• /
• v.19 no.4
• /
• pp.159-163
• /
• 2012

An appropriate research design for hypotheses and purposes leads to a good quality of research results. In this review article, we summarized the types of research methods and described the characteristics of clinical trials. Research designs are categorized into observational studies and experimental ones, depending on data collecting methods. In an observational study, there are cross-sectional, cohort and case-control studies. Parallel groups design and crossover trial studies are representative designs in a randomized controlled trial study, a kind of experimental study. Clinical researchers should understand the characteristics of clinical research designs including advantages and disadvantages and choose the suitable design according to their study purposes and the nature of collected data or subjects.

• Genomics & Informatics
• /
• v.17 no.4
• /
• pp.46.1-46.7
• /
• 2019

The implications of germline de novo variants (DNVs) in diseases are well documented. Despite extensive research, inconsistencies between studies remain a challenge, and the distribution and genetic characteristics of DNVs need to be precisely evaluated. To address this issue at the whole-genome scale, a large number of DNVs identified from the whole-genome sequencing of 1,902 healthy trios (i.e., parents and progeny) from the Simons Foundation for Autism Research Initiative study and 20 healthy Korean trios were analyzed. These apparently nonpathogenic DNVs were enriched in functional elements of the genome but relatively depleted in regions of common copy number variants, implying their potential function as triggers of evolution even in healthy groups. No strong mutational hotspots were identified. The pathogenicity of the DNVs was not strongly elevated, reflecting the health status of the cohort. The mutational signatures were consistent with previous studies. This study will serve as a reference for future DNV studies.

• Genomics & Informatics
• /
• v.12 no.4
• /
• pp.216-224
• /
• 2014

Gastritis is a common but a serious disease with a potential risk of developing carcinoma. Helicobacter pylori infection is reported as the most common cause of gastritis, but other genetic and genomic factors exist, especially single-nucleotide polymorphisms (SNPs). Association studies between SNPs and gastritis disease are important, but results on epistatic interactions from multiple SNPs are rarely found in previous genome-wide association (GWA) studies. In this study, we performed computational GWA case-control studies for gastritis in Korea Associated Resource (KARE) data. By transforming the resulting SNP epistasis network into a gene-gene epistasis network, we also identified potential gene-gene interaction factors that affect the susceptibility to gastritis.

• Journal of Labour Economics
• /
• v.37 no.2
• /
• pp.79-103
• /
• 2014

Previous studies show that tall people have better labor market outcomes, but controlling for their abilities reduces the size of height effects. This implies that a failure to properly control for one's ability could overestimate the OLS estimate. This paper contributes to the literature by being the first to control for individual fixed effects (FE) and to examine height effects on the probability of one's attaining a leadership position. The data used are panel data of a cohort obtained during the cohort's middle and high school years. In OLS estimation, this paper finds positive height effects for boys. However, when controlling for individual fixed effects, the estimate is not statistically significant. For girls, the height effects are found on neither OLS nor FE model.

• Molecular & Cellular Toxicology
• /
• v.3 no.1
• /
• pp.68-75
• /
• 2007

[ $\alpha$ ]-Terpinene has been known as a repellent against the mosquito Culex pipiens pallens Coquillett based on a human forearm bioassay. $\alpha$-Terpinene showed significantly greater repellency than a commercial formulation, N, N-diethyl-m-methylbenzamide (deet). In this study, skin and eye sensitivity of $\alpha$-terpinene (2%) was examined with bioassays using white New Zealand rabbits. There were somewhat gross and histological changes observed in these treatments. Eye irritancy assays examined gross changes to cornea, iris and conjuctiva, and histological changes to smear of ocular discharge and eye tissue. Treated rabbits were divided into two cohorts, a saline washed cohort (W) or a non-washed cohort (NW). Opacity of cornea and redness, chemosis and discharge of conjuctiva were observed in both cohorts, but disappeared within 4 and 10 days in W and NW, respectively. Main components of ocular discharges were fibrin, epithelial or epitheloid cells, lymphoid cells, erythrocytes and granulocytes. These abnormal cellular components disappeared within 4 days and 10 days in W and NW, respectively. No permanent histological differences were observed between the two cohorts. However, severe irritation was determined as 57.2 of I.I.O.I value on the first day after treatment. These findings indicate a spray-type solution containing 2% $\alpha$-terpinene may serve as an alternative mosquito repellent and further studies need to reduce the eye irritation with formulation changes.

• Journal of Korean Academy of Nursing
• /
• v.49 no.6
• /
• pp.713-723
• /
• 2019

Purpose: The purpose of this study was to identify the impact of cigarette smoking and alcohol consumption on the incidence of colon cancer in adults with metabolic syndrome. Methods: This study employed a longitudinal study design and utilized secondary data drawn from the Korean Genome and Epidemiology Study (KoGES). The data of a sample of 2,327 adults with metabolic syndrome tracked every two years from 2001 to 2014 were used in this study. Statistical data analyses of the frequency, number of cases per 100,000 person-years, log-rank test, Kaplan-Meier curve, and Cox's proportional hazards regression were performed using IBM SPSS statistics version 24. Results: During the observation period, the number of colon cancer cases was 46, and the total person-years were 252,444. The incidence of colon cancer was higher in current, over 10 pack-year smokers when compared to non-smokers (hazard ratio=3.38, 95% confidence interval=1.09~8.42). Conclusion: Excessive and long-term smoking should be avoided to prevent colon cancer, especially in adults with metabolic syndrome, since it might exacerbate the risk factors of colon cancer. Particularly, health professionals need to provide individualized smoking cessation interventions to those at high risk of colon cancer.