• Communications for Statistical Applications and Methods
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• 제11권1호
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• pp.181-187
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• 2004

One of objectives in epidemiologic studies is to detect the amount of change caused by a specific risk factor. Risk ratio is one of the most useful measurements in epidemiology. When we perform the inference for this measurement with rare events, the standard approach based on the normal approximation may fail, in particular when there are no disease cases observed. In this paper, we discuss and evaluate several existing methods for constructing a confidence interval of risk ratio through simulation when the disease of interest is a rare event. The results in this paper provide guidance with how to construct interval estimates for risk difference and risk ratio when there are no disease cases observed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1997년도 봄 학술발표회 논문집
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• pp.27-34
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• 1997

In this paper, systematic and comprehensive approaches are suggested for the application of quantitative PRA techniques especially for those risk events that cannot be easily evaluated quantitatively In addition, dominant risk events are identified based on their occurrence frequency assessed by both actual survey of construction site conditions and the statistical data related with the probable accidents. Practical FTA(Fault Tree Analysis) and ETA(Event Tree Analysis) models are used for the assessment of the identified risks. When the risk events are lack of statistical data, appropriate Bayesian models incorporating engineering judgement and test results are also introduced in this paper. Moreover, a fuzzy probability technique is used for the quantitative risk assessment of those risk components which are difficult to evaluate quantitatively.

• Nuclear Engineering and Technology
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• 제53권2호
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• pp.376-385
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• 2021

Probabilistic risk assessment (PRA) has improved its elemental technologies used for assessing external events since the Fukushima Daiichi Nuclear Power Station Accident in 2011. HRA needs to be improved for analyzing tasks performed under extreme conditions (e.g., different actors responding to external events or performing operations using portable mitigation equipment). To make these improvements, it is essential to understand plant-specific and scenario-specific conditions that affect human performance. The Nuclear Risk Research Center (NRRC) of the Central Research Institute of Electric Power Industry (CRIEPI) has developed an HRA guide that compiles qualitative analysis methods for collecting plant-specific and scenario-specific conditions that affect human performance into "narratives," reflecting the latest research trends, and models for analysis of tasks under extreme conditions.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.1037-1045
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• 2006

In this study, a hazard analysis was performed on the accident related work in the operational railway during 2000-2006 years in order to establish risk assesment procedure for work in the operational railway. As a result of hazard analysis, various hazard events for person accident and operation incident were identified, and risk for the each events was evaluated. Also risk matrix was structurized for setting the risk control criteria.

• 지질동맥경화학회지
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• 제7권2호
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• pp.110-121
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• 2018

Objective: We developed a new equation for predicting coronary heart disease (CHD) risk in Korean diabetic patients using a hospital-based cohort and compared it with a UK Prospective Diabetes Study (UKPDS) risk engine. Methods: By considering patients with type 2 diabetes aged ${\geq}30years$ visiting the diabetic center in Boramae hospital in 2006, we developed a multivariable equation for predicting CHD events using the Cox proportional hazard model. Those with CHD were excluded. The predictability of CHD events over 6 years was evaluated using area under the receiver operating characteristic (AUROC) curves, which were compared using the DeLong test. Results: A total of 732 participants (304 males and 428 females; mean age, $60{\pm}10years$; mean duration of diabetes, $10{\pm}7years$) were followed up for 76 months (range, 1-99 month). During the study period, 48 patients (6.6%) experienced CHD events. The AUROC of the proposed equation for predicting 6-year CHD events was 0.721 (95% confidence interval [CI], 0.641-0.800), which is significantly larger than that of the UKPDS risk engine (0.578; 95% CI, 0.482-0.675; p from DeLong test=0.001). Among the subjects with <5% of risk based on the proposed equation, 30.6% (121 out of 396) were classified as ${\geq}10%$ of risk based on the UKPDS risk engine, and their event rate was only 3.3% over 6 years. Conclusion: The UKPDS risk engine overestimated CHD risk in type 2 diabetic patients in this cohort, and the proposed equation has superior predictability for CHD risk compared to the UKPDS risk engine.

• Asian Pacific Journal of Cancer Prevention
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• 제17권sup3호
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• pp.245-252
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• 2016

Due to increasing incidence of breast cancer, recognition of risk factors has become increasingly important. Over the past few decades, among risk factors of this disease, stressful life events have attracted particular attention, but their relationship with breast cancer incidence and survival remains a mystery. This study aimed to examine the relationship between severe stressful life events and incidence and survival of women with breast cancer. In this case-control study, using a structured telephone interview with 355 women with breast cancer and also with 516 women with benign breast diseases who were matched in demographic characteristics, necessary information about the experience of major stressful events in the years before the diagnosis were collected. Data were analyzed using statistical methods of ${\chi}^2$, t, and Kaplan-Meier with a significance level of <0.05. Generally, in the case and control groups, there were no significant association between experience of stressful life events and incidence of breast cancer. Regarding associations between each of the events and incidence of breast cancer only "severe interpersonal problems with spouse" was significant. In the breast cancer group, even after controlling confounding variables, there was no significant association between major stressful events and disease-free survival, or overall 5-and 10-year survival. In this study, only "severe interpersonal problems with spouse" was confirmed as a risk factor. This result can be useful in developing preventive policies. More research regarding the interactive effects of psycho-social factors in the incidence and survival of breast cancer with stressful life events is recommended.

• 한국터널지하공간학회 논문집
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• 제18권5호
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• pp.453-467
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• 2016

본 논문에서는 쉴드 TBM 시공 시 발생 가능한 사건 및 원인의 규명, 리스크 발생의 인과관계 규명, 리스크의 위험도 판별, 리스크의 저감대책 제시를 통한 쉴드 TBM의 전반적인 시공 리스크 관리에 대한 연구를 수행하였다. 이를 위해서 쉴드 TBM의 사고 사례에 대한 문헌조사, 설계 및 시공 전문가 인터뷰를 수행하였다. 리스크 사건은 절삭량 저하, 막장면 붕괴, 지반 침하, 지반 융기, 이수 분출, 배토 불능, 굴착 불가, 지하수 누수의 8개의 그룹으로 나뉘어졌다. 리스크의 원인은 지질 원인, 설계 원인, 시공관리 원인의 3가지 그룹으로 나뉘어졌다. 리스크 원인과 사건간의 인과관계를 체계적으로 분석하기 위하여 베이지안 네트워크를 이용한 도식적인 관계도를 작성하였다. 리스크의 위험도를 산정하기 위하여 리스크가 발생하였을 때 이를 복구하기 위한 다운타임 및 비용을 기준으로 전문가를 대상으로 Analytic Hierarchy Process (AHP)를 수행하였으며, 위험도 결과에 기반하여 리스크 대응단계를 제시하고 이를 실제 리스크 발생사례와 비교하여 검증하였다. 또한 발생 가능한 리스크에 대응하기 위하여 설계 및 시공단계에서의 리스크 저감대책을 제안하였다. 제안된 연구는 TBM 설계자 및 시공자가 현장의 조건을 고려하여 리스크 원인을 선정하고 이로 인해 발생 가능한 리스크를 체계적으로 분석하여 파악할 수 있게 해주며, 리스크의 위험도의 판별 및 그에 대한 설계 및 시공단계에서의 저감대책을 통해 체계적인 쉴드 TBM 리스크 관리에 도움을 줄 수 있다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권4호
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• pp.2453-2459
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• 2013

Bevacizumab has been approved for use in combination with chemotherapy to treat many types of cancer but associated neutropenic events, including febrile neutropenia, have been reported. To estimate the incidence and relative risk of neutropenic events in cancer patients treated with bevacizumab combination therapy, we searched PubMed, EMBASE, and Web of Science literature databases, as well as abstracts presented at the American Society of Clinical Oncology conferences, to identify relevant studies published from January 1966 to December 2011. Studies that compared bevacizumab plus chemotherapy or biological therapy with chemotherapy or biological therapy alone, and that had adequate safety data profiles, were selected for analysis. Statistical analyses were conducted to calculate the summary incidence rates, relative risks (RRs), and 95% confidence intervals (CIs) using fixed- or random-effects models. A total of 22 clinical trials involving 15,056 patients were included in the analysis. The summary incidences of high-grade neutropenia (HGN) and high-grade febrile neutropenia (HGFN) in patients receiving bevacizumab was 27.3% (95% CI: 26.4%-28.3%) and 3.91% (95% CI: 3.51%-4.37%), respectively. The risks of HGN (RR=1.10; 95% CI: 1.02-1.19; P=0.02) and HGFN (RR=1.31; 95% CI: 1.08-1.59; P=0.005) were significantly increased in bevacizumab-treated patients, compared to those who did not receive bevacizumab. The RR of bevacizumab-associated HGN, but not HGFN, varied significantly with tumor types (P=0.005). The increased risk of bevacizumab-associated neutropenic events was dose-dependent, as the RR was greater at a dose of 5 mg/kg/week than at 2.5 mg/kg/week. Our findings suggest that bevacizumab addition to cancer therapy significantly increases the risk of serious neutropenic events, and this risk may be dose-dependent.

• 대한핵의학회지
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• 제33권3호
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• pp.273-281
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• 1999

목적: 우리는 비심장 수술 환자에서 수술전후의 심장사건의 위험도를 평가할 때 미국 순환기학회/미국 심장학회(이하ACC/AHA)에서 제시한 임상적 여러 지표에 더하여 심근관류 SPECT가 도움되는지 연구하였다. 대상 및 방법: 1997년에 비심장 수술을 시행한 118명(혈관수술 18, 비혈관수술 100)을 대상으로 수술 전에 휴식 T1-201/부하 Tc-99m MIBI 심근관류 SPECT를 시행하고 중한 심장사건과 경한 심장사건의 발생을 조사하였다. 임상적 지표, 운동능력, 수술 종류에 따라 분류한 것의 심장사건 예측률과 심근관류 SPECT 소견을 가역관류감소, 지속관류감소, 정상으로 나누었을 때 심장사건 예측률을 조사하였다. 임상적 지표들에 대해 심근관류 SPECT가 부가 효용이 있는지 다변량 로짓 회귀분석을 하였다. 결과: 심장사건은 전체 환자의 21%에서 발생하였으며 심근관류 SPECT에 가역적 심근관류 이상이 있는 경우에 심장사건의 발생빈도가 높았다. 임상적 분류와 수술 종류도 사건 발생을 예측할 수 있었으나 다변량 분석에 수술 종류(p=0.0018)와 심근관류 SPECT 소견(p=0.0001)이 유의한 예측지표이었다. 심근관류 SPECT 결과가 수술 종류에 따른 위험 예측을 더욱 계층화할 수 있었다. 결론: 비심장수술 환자에서 수술 종류에 더하여 심근관류 SPECT가 심장사건 발생을 예측하는 유용한 지표이었다.

• Journal of Preventive Medicine and Public Health
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• 제43권6호
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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.