• Communications for Statistical Applications and Methods
• /
• v.26 no.6
• /
• pp.557-573
• /
• 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.

• Journal of Korean Society for Quality Management
• /
• v.47 no.3
• /
• pp.571-582
• /
• 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.

• Korean Journal of Community Nutrition
• /
• v.20 no.4
• /
• pp.301-309
• /
• 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.

• Journal of Environmental Health Sciences
• /
• v.35 no.4
• /
• pp.249-258
• /
• 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.

• Fire Science and Engineering
• /
• v.29 no.5
• /
• pp.57-66
• /
• 2015

This thesis is based on a research to investigate the electrical fire risk due to the single and composite cause in a terminal block. This paper analyzed the thermal characteristics depending on the screw torque change and contact resistance change to measure the fire risk due to the poor contact from single cause first. To measure the fire risk due to the composite cause, the acceleration tracking depending on the contact resistance change was experimented to check the correlation of poor contact and tracking to fire. The experiment result showed that the thermal characteristics were clearer as the screw torque in poor contact status and magnitude of contact resistance increased and that the thermal characteristics of terminal block depending on the contact resistance change was more reliable than the thermal characteristics depending on the screw torque change. Moreover, the terminal block poor contact and tracking were correlated in the case of the composite cause, and when two composite causes were interacted, the electrical fire risk was higher than the single cause.

• Journal of the Korean Society of Safety
• /
• v.33 no.3
• /
• pp.83-91
• /
• 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.

• Health Policy and Management
• /
• v.25 no.3
• /
• pp.197-206
• /
• 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.

• Fire Science and Engineering
• /
• v.31 no.4
• /
• pp.111-118
• /
• 2017

The present paper is a study on the risk analysis of complex electrical fire by the partial disconnection and tracking. First, in order to analysis the single cause of electrical fire risk by the partial disconnection, the thermal characteristic has been measured by the change in the number of strands and the rated current of a wire. And then, in order to analysis the electrical fire risk by complex cause, an experiment on the accelerated tracking has been carried out in a condition of partial disconnection and confirmed the fire relation between partial disconnection and tracking. From the experiment, if the partial wire disconnection acts as a single cause, the existing thermal characteristics generated by the flowing current has appeared more clearly by the increase in the flowing current due to the complex action of tracking. Accordingly, the disconnection of strands has appeared by the complex cause due to the drastic temperature increase which was not generated in the single cause. Namely, it has been confirmed that if the partial disconnection and tracking act complexly rather than the risk of electrical fire by the existing partial disconnection, relatively its risk has been increased in large.

• Journal of the Korean Society of Safety
• /
• v.31 no.4
• /
• pp.136-142
• /
• 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
• /
• v.83 no.4
• /
• pp.268-275
• /
• 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.