• Communications for Statistical Applications and Methods
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• 제26권6호
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• pp.557-573
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• 2019

Mortality study is an essential component of actuarial risk management for life insurance policies, annuities, and pension plans. Life expectancy has drastically increased over the last several decades; consequently, longevity risk associated with annuity products and pension systems has emerged as a crucial issue. Among the various aspects of mortality study, a consideration of the cause-of-death mortality can provide a more comprehensive understanding of the nature of mortality/longevity risk. In this case study, the cause-of-mortality data in Korea and the US were analyzed along with a multinomial logistic regression model that was constructed to quantify the impact of mortality reduction in a specific cause on actuarial values. The results of analyses imply that mortality improvement due to a specific cause should be carefully monitored and reflected in mortality/longevity risk management. It was also confirmed that multinomial logistic regression model is a useful tool for analyzing cause-of-death mortality for actuarial applications.

• 품질경영학회지
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• 제47권3호
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• pp.571-582
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• 2019

Purpose: To develop a risk metric for failure cause that can help determine the action priority of each failure cause in FMEA considering time sequence of cause- failure- detection. Methods: Assuming a quadratic loss function the unfulfilled mission period, a risk metric is obtained by deriving the failure time distribution. Results: The proposed risk metric has some reasonable properties for evaluating risk accompanied with a failure cause. Conclusion: The study may be applied to determining action priorities among all the failure causes in the FMEA sheet, requiring further studies for general situation of failure process.

• 대한지역사회영양학회지
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• 제20권4호
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• pp.301-309
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• 2015

Objectives: While recent studies showed that coffee consumption reduced the risk of all-cause mortality, no study has examined the effect of coffee consumption on all-cause mortality related to sleep disorders. We aimed to examine whether sleep-related disorders would differently affect the association between coffee consumption and the risk of all-cause mortality among 8,075 adults aged 40 to 69 years. Methods: In a prospective cohort study, the study participants were biennially followed up for 12 years from 2001 to 2012. On each follow-up visit, the participants underwent comprehensive tests including anthropometric examinations, interviewer-administered questionnaires, and biochemical tests. Coffee consumption frequency and the amount were measured using a semi-quantitative food frequency questionnaire. Using death certificate data from Korean National Statistical Office, the vital status of each study participant was identified. Sleep-related disorders were examined with interviewer-administered questionnaires. We estimated Hazard ratios and the corresponding 95% confidence intervals from Cox Proportional Hazard models. Multivariable models were established after adjusting for center, total caloric intake, age, gender, body mass index, physical activity, education, smoking, drinking, hypertension, diabetes, total cholesterol, c-reactive protein, energy-adjusted food groups of refined grains, vegetables, fruits, meat, fish, and dairy. Results: Compared with those who had no coffee consumption, participants who had about three cups of coffee per day showed a reduced risk of all-cause mortality, after adjusting for covariates. Those who had a sleep-related disorder showed no significant effect of coffee consumption on the risk of all-cause mortality, whereas those who had no sleep-related disorders showed significantly reduced risk of all-cause mortality. Conclusions: Our findings suggested that approximately three cups of coffee per day would be beneficial to reduce the risk of all-cause mortality only among adults with no sleep-related disorders. Coffee consumption should be prudent for those with sleep-related symptoms.

• 한국환경보건학회지
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• 제35권4호
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• pp.249-258
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• 2009

The objectives of this study were to compare the relative risk of all-cause mortality and cause-specific mortality associated with Asian dust events, and especially to investigate the effects on the susceptible population such as the elderly and children, which were based on the data in Seoul from 2000 to 2006. Both of the study periods with/without Asian dust days, respiratory-cause mortality was the highest, followed by cardiovascular-cause mortality and all-cause mortality in sequence among mortality related to air pollution for all-aged group. As to susceptible group, the relative risk of mortality is the highest for +65 yrs group among all-cause mortality. According to comparison of mortality with/without Asian dust days, the relative risk of all-cause mortality is larger in the model with Asian dust days than the one in the model without Asian dust days among all age group (except for under 15 yrs group) and all air pollutants. The relative risk of cause-specific mortality (except for ozone in under 15 yrs group in case of respiratory-cause mortality, and ozone in all age group and over 65 yrs group in case of cardiovascular-cause mortality) per IQR increase of each pollutant is larger in the model without Asian dust days.

• 한국화재소방학회논문지
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• 제29권5호
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• pp.57-66
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• 2015

본 논문은 단자대에서 단일원인 및 복합원인에 의한 전기화재위험성을 규명하기 위한 연구이다. 우선적으로 단일원인인 접촉불량에 의한 화재위험성을 측정하기 위해 조임토크변화 및 접촉저항변화에 따른 열적특성을 분석하였다. 또한, 복합원인에 의한 화재위험성을 측정하기 위해 접촉저항변화에 따른 가속트래킹 실험을 실시하여 접촉불량과 트래킹의 화재연관성을 확인하였다. 실험결과 단일원인의 경우 접촉불량상태의 조임토크 및 접촉저항 크기가 증가할수록 열적특성이 뚜렷하게 나타나는 것을 확인할 수 있었고, 접촉저항변화에 따른 열적특성이 조임토크변화에 따른 열적특성보다 그 특성이 더 잘 나타났다. 또한, 복합원인의 경우 단자대 접촉불량과 트래킹은 상호연관성을 가지고 있으며, 두 가지의 복합적인 원인이 서로 작용될 경우 기존의 단일원인의 전기화재 위험성보다 상대적인 위험성이 더욱 높게 나타나는 것으로 도출되었다.

• 한국안전학회지
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• 제33권3호
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• pp.83-91
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• 2018

This paper suggests a weibull time delay model to evaluate failure risks in FMEA(failure modes and effects analysis). Assuming three types of loss functions for delayed time in failure cause detection, the risk of each failure cause is evaluated as its occurring frequency and expected loss. Since the closed form solution of the risk metric cannot be obtained, a statistical computer software R program is used for numerical calculation. When the occurrence and detection times have a common shape parameter, though, some simple results of mathematical derivation are also available. As an enormous quantity of field data becomes available under recent progress of data acquisition system, the proposed risk metric will provide a more practical and reasonable tool for evaluating the risks of failure causes in FMEA.

• 보건행정학회지
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• 제25권3호
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• pp.197-206
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• 2015

Background: The purpose of this study was to propose a method for developing a measure of hospital-wide all-cause risk-standardized readmissions using administrative claims data in Korea and to discuss further considerations in the refinement and implementation of the readmission measure. Methods: By adapting the methodology of the United States Center for Medicare & Medicaid Services for creating a 30-day readmission measure, we developed a 6-step approach for generating a comparable measure using Korean datasets. Using the 2010 Korean National Health Insurance (NHI) claims data as the development dataset, hierarchical regression models were fitted to calculate a hospital-wide all-cause risk-standardized readmission measure. Six regression models were fitted to calculate the readmission rates of six clinical condition groups, respectively and a single, weighted, overall readmission rate was calculated from the readmission rates of these subgroups. Lastly, the case mix differences among hospitals were risk-adjusted using patient-level comorbidity variables. The model was validated using the 2009 NHI claims data as the validation dataset. Results: The unadjusted, hospital-wide all-cause readmission rate was 13.37%, and the adjusted risk-standardized rate was 10.90%, varying by hospital type. The highest risk-standardized readmission rate was in hospitals (11.43%), followed by general hospitals (9.40%) and tertiary hospitals (7.04%). Conclusion: The newly developed, hospital-wide all-cause readmission measure can be used in quality and performance evaluations of hospitals in Korea. Needed are further methodological refinements of the readmission measures and also strategies to implement the measure as a hospital performance indicator.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.111-118
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• 2017

본 논문은 반단선과 트래킹에 의한 복합적 전기화재의 위험성분석에 관한 연구이다. 먼저, 단일원인인 반단선에 의한 전기화재 위험성을 분석하기 위해 전선의 소선 수 및 정격전류의 변화에 따른 열적특성을 측정하였다. 또한, 그 후 복합적 원인에 의한 전기화재 위험성을 분석하기 위해 반단선 상태에서 추가적으로 가속트래킹 실험을 실시하여 반단선과 트래킹의 화재연관성을 확인하였다. 실험결과 반단선이 단일원인으로 작용할 때의 전류에 의해 발생된 기존 열적특성과 트래킹이 복합적으로 작용함으로써 전류가 크게 증가되어 열적특성이 더욱 뚜렷이 나타나 단일원인에서 발생되지 않았던 급격한 온도상승으로 인한 소선의 단선이 복합적 원인에서 나타났다. 즉, 기존의 반단선에 의한 전기화재 위험성보다 반단선과 트래킹이 복합적으로 작용될 경우 상대적으로 그 위험성이 크게 증가되는 것을 확인할 수 있었다.

• 한국안전학회지
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• 제31권4호
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• pp.136-142
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• 2016

The FMEA is a widely used technique to pre-evaluate and avoid risks due to potential failures for developing an improved design. The conventional FMEA does not consider the possible time gap between occurrence and detection of failure cause. When a failure cause is detected and corrected before the failure itself occurs, there will be no other effect except the correction cost. But, if its cause is detected after the failure actually occurs, its effects will become more severe depending on the duration of the uncorrected failure. Taking this situation into account, a risk metric is developed as an alternative to the RPN of the conventional FMEA. The severity of a failure effect is first modeled as linear and quadratic severity functions of undetected failure time duration. Assuming exponential probability distribution for occurrence and detection time of failures and causes, the expected severity is derived for each failure cause. A new risk metric REM is defined as the product of a failure cause occurrence rate and the expected severity of its corresponding failure. A numerical example and some discussions are provided for illustration.

• Tuberculosis and Respiratory Diseases
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• 제83권4호
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• pp.268-275
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• 2020

Background: It is not evident that the attributable risk of smoking on mortality in Korea has decreased. We investigated the impact of smoking on all-cause mortality and estimated the attributable risk of smoking in Korean adults. Methods: Those aged ≥20 years with smoking history in the Korean National Health and Nutrition Examination Surveys (KNHANES) 2007-2015 were enrolled. We categorized the participants into three groups as follows: never smoker, <20 pack-years (PY) smokers, and ≥20 PY smokers. We applied inverse probability weighting using propensity scores to control various confounders between the groups. All-cause mortality risks were compared between the groups using the Kaplan-Meier log-rank test. The effects of smoking-attributable risks (ARs) on mortality were also calculated. Results: A total of 50,458 participants were included. Among them, 19,334 (38.3%) were smokers and 31,124 (61.7%) were never smokers. Those with a smoking history of 20 PY or more (≥20 PY smokers), those with a smoking history of less than 20 PY (<20 PY smokers), and never smokers were 18.1%, 20.2%, and 61.7%, respectively, of the study population. Smokers had a higher risk of all-cause mortality compared to never smokers (log-rank test p<0.01). The ARs of smoking were 21.8% (95% confidence interval [CI], 5.7%-37.9%) and 9.0% (95% CI, 6.1%-12.0%) in males and females, respectively. ARs decreased from 24.2% to 19.5% in males and from 9.5% to 4.1% in females between 2007-2010 and 2011-2015. Conclusion: Our study using KNHANES IV-VI data demonstrated that smoking increased the risk of all-cause mortality in a dose-response manner and the ARs of smoking on mortality were 21.8% in males and 9.0% in females during 2007-2015. This suggests that the ARs of smoking on mortality have decreased since around 2010.