• The Korean Journal of Pain
• /
• 제33권2호
• /
• pp.153-165
• /
• 2020

Background: Well-validated risk prediction models help to identify individuals at high risk of diseases and suggest preventive measures. A recent systematic review reported lack of validated prediction models for low back pain (LBP). We aimed to develop prediction models to estimate the 8-year risk of developing LBP and its recurrence. Methods: A population based prospective cohort study using data from 435,968 participants in the National Health Insurance Service-National Sample Cohort enrolled from 2002 to 2010. We used Cox proportional hazards models. Results: During median follow-up period of 8.4 years, there were 143,396 (32.9%) first onset LBP cases. The prediction model of first onset consisted of age, sex, income grade, alcohol consumption, physical exercise, body mass index (BMI), total cholesterol, blood pressure, and medical history of diseases. The model of 5-year recurrence risk was comprised of age, sex, income grade, BMI, length of prescription, and medical history of diseases. The Harrell's C-statistic was 0.812 (95% confidence interval [CI], 0.804-0.820) and 0.916 (95% CI, 0.907-0.924) in validation cohorts of LBP onset and recurrence models, respectively. Age, disc degeneration, and sex conferred the highest risk points for onset, whereas age, spondylolisthesis, and disc degeneration conferred the highest risk for recurrence. Conclusions: LBP risk prediction models and simplified risk scores have been developed and validated using data from general medical practice. This study also offers an opportunity for external validation and updating of the models by incorporating other risk predictors in other settings, especially in this era of precision medicine.

• 한국산림과학회지
• /
• 제113권2호
• /
• pp.187-197
• /
• 2024

본 연구에서는 콕스 비례위험모형을 이용하여 산불피해 소나무의 고사에 영향을 미치는 인자를 밝히고자 하였다. 지표화 피해 소나무를 대상으로 고사 영향 인자를 조사하고 산불 발생 7년 차까지 고사 발생 모니터링을 수행하였다. 수집된 자료를 기반으로 생존분석을 실시하였다. 분석 결과, 고사 위험성을 증가시키는 변수는 dNDVI(delta Normalized Difference Vegetation Index), dNBR(delta Normalized Burn Ratio), 경사, 나무에 남겨진 그을음의 상대적인 면적과 평균적인 높이를 나타내는 수피 그을음 지수(Bark Scorch Index, BSI)와 수피 그을음 높이(Bark Scorch Height, BSH)로 나타난 반면, 음의 관계를 가지는 변수는 고도, 흉고직경, 수관층 수분스트레스 변화를 나타내는 수분스트레스지수(dleta Moisture Stress Index, dMSI)로 나타났다(p<0.001). 콕스 비례위험모형의 유의성을 확인하기 위한 변수별 비례위험가정검증에서는 사면방향을 제외한 모든 인자가 모형에 적합하며 고사 발생에 유의미한 영향을 미치는 것으로 나타났다. 생존 곡선 분석에서 가장 큰 생존율 차이를 보인 변수는 BSI였으며(p<0.0001), 원격탐사를 통해 얻어진 환경변화 인자들(dNDVI, dNBR, dMSI) 역시 큰 생존율 차이를 나타내었다(p<0.0001). 이러한 결과는 산불 이후 소나무의 잠재적인 고사위험성을 고려한 복원계획 수립을 위한 기초자료로 활용될 것으로 기대된다.

• Communications for Statistical Applications and Methods
• /
• 제14권2호
• /
• pp.317-327
• /
• 2007

In this paper, we propose a simple estimate of relative risk based on a functional equation. We derive the asymptotic normality with a restricted condition. Then we discuss some interesting features as concluding remarks. Finally we comment briefly about application of the estimate to the testing problems and compare our estimate with that of Begun through simulation study.

• East Asian Economic Review
• /
• 제21권1호
• /
• pp.3-27
• /
• 2017

This paper studied the effects of anti-dumping measures on the imports to investigate whether the trade restriction effect of an anti-dumping duty is dominant. Our results indicate that a 1% increase in the anti-dumping duties decreases the import of the targeted product by about 0.43~0.51%. The actual statistics, however, show that the total import of the targeted products increased by about 30 percent while an anti-dumping duty was in force. That indicates that an anti-dumping duty is just a temporary import relief. This paper also investigated whether an anti-dumping duty is terminated in the case that the injury would not be likely to continue or recur if the duty were removed. The hazards model estimates show that increase in market share, MFN tariff rate, and dumping margin decrease the hazard of termination of an anti-dumping duty, but the increase in value added increases the hazard of termination. Generally speaking, this result indicates that the WTO member countries have regulated the overuse of an anti-dumping measure. The findings of this paper show that there is a country- and industry-wise heterogeneous characteristic in the effect as well as termination of an anti-dumping duty.

• 한국생물정보학회:학술대회논문집
• /
• 한국생물정보시스템생물학회 2005년도 BIOINFO 2005
• /
• pp.357-360
• /
• 2005

In this paper we consider the well-known semiparametric proportional hazards (PH) models for survival analysis. These models are usually used with few covariates and many observations (subjects). But, for a typical setting of gene expression data from DNA microarray, we need to consider the case where the number of covariates p exceeds the number of samples n. For a given vector of response values which are times to event (death or censored times) and p gene expressions (covariates), we address the issue of how to reduce the dimension by selecting the significant genes. This approach enable us to estimate the survival curve when n < < p. In our approach, rather than fixing the number of selected genes, we will assign a prior distribution to this number. The approach creates additional flexibility by allowing the imposition of constraints, such as bounding the dimension via a prior, which in effect works as a penalty. To implement our methodology, we use a Markov Chain Monte Carlo (MCMC) method. We demonstrate the use of the methodology to diffuse large B-cell lymphoma (DLBCL) complementary DNA(cDNA) data.

• Asian Pacific Journal of Cancer Prevention
• /
• 제13권11호
• /
• pp.5505-5510
• /
• 2012

Objective: The aim of this retrospective study is to analyze the clinical and pathological factors related to the prognosis of Chinese patients with stage Ib to IIb cervical cancer. Methods and Results: 13 clinical pathological factors in 255 patients with stage Ib to IIb cervical cancer undergoing radical hysterectomy and systematic lymphadenectomy were analyzed to screen for factors related to prognosis. The cumulative 5-year survival of the 255 patients was 75.7%. The result of the univariate analysis suggested that clinical stage, cell differentiation, depth of cervical stromal invasion, parametrial tissue involvement, and lymph node metastasis were prognostic factors for patients with stage Ib to IIb cervical cancer (P<0.05). Compared with cases with involvement of iliac nodes, obturator nodes, or inguinal lymph nodes, cases with metastasis to the common iliac lymph nodes had a poorer prognosis (P<0.05). Cases with involvement of four or more lymph nodes had a poorer prognosis than those with involvement of three or fewer lymph nodes (P<0.05). Using multivariate Cox proportional hazards model regression analysis, non-squamous histological type, poor differentiation, parametrial tissue involvement, and outer 1/3 stromal invasion were found to be independently related to patients poor prognosis (P<0.05). Conclusion: Non-squamous histological type, poor cell differentiation, parametrial tissue involvement, and outer 1/3 stromal invasion are the independent poor prognostic factors for patients with stage Ib to IIb cervical cancer.

• 응용통계연구
• /
• 제34권2호
• /
• pp.255-266
• /
• 2021

본 연구는 미국 국립암연구소의 SEER 프로그램에서 제공하는 위암 3기 자료에 대해 항암치료의 효과를 비교하고 위암 생존율에 유의한 영향을 미치는 요인을 알아보고자 한다. 본 연구에서 분석한 위암 3기 자료는 비례위험 가정이 성립하지 않아 대안으로 제한된 평균 생존시간을 이용한 분석 방법을 자료 분석에 적용하였다. 의사-관측들을 이용하여 제한된 평균 생존시간을 추정하였고, 제한된 평균 생존시간 추정량에 기반한 검정통계량을 이용하여 항암치료의 효과를 파악하였다. 일반화 선형모형을 이용한 회귀모형을 통해 위암 3기 환자의 평균 생존시간에 유의한 영향을 미치는 공변량들의 효과를 추정하였다. 항암치료법에 따라 위암 3기 환자의 평균 생존시간에 유의한 차이가 있음을 확인하였고, 진단연령, 인종, 세분화병기, 분화도, 종양의 크기, 수술여부, 항암치료가 위암 3기 환자의 평균 생존시간에 유의한 영향을 미치는 요인들이였으며, 그 중 수술여부가 위암 3기 환자의 평균 생존시간을 늘리는데 가장 큰 영향을 미치는 요인임을 확인하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2008년도 추계학술대회A
• /
• pp.1387-1390
• /
• 2008

Pneumatic cylinder is widely used in the various industrial fields. Reliability Study of this field is very important part to the related companies. In this study, we want to predict the life of pneumatic cylinder using Cox (or proportional hazards) model. Used in biomedical applications, the Cox model can be used as an accelerated life testing model. We considered working pressure and temperature as stress factors. The statistical software is used to analyze and forecast the life data.

• Journal of the Korean Statistical Society
• /
• 제24권2호
• /
• pp.537-549
• /
• 1995

In this article, we propose a class of weighted estimators for the excess risk in additive risk model with a binary covariate. The proposed estimator is consistent and asymptotically normal. When the assumed model is inappropriate, however, the estimators with different weights converge to nonidentical constants. This fact enables us to develop a goodness-of-fit test for the excess assumption by comparing estimators with diffrent weights. It is shown that the proposed test converges in distribution to normal with mean zero and is consistent under the model misspecifications. Furthermore, the finite-sample properties of the proposed test procedure are investigated and two examples using real data are presented.

• 상하수도학회지
• /
• 제23권3호
• /
• pp.305-313
• /
• 2009

This paper provides a method for evaluating a residual life of water mains using a proportional hazard model(PHM). The survival time of individual pipe is defined as the elapsed time since installation until a break rate of individual pipe exceeds the Threshold Break Rate. A break rate of an individual pipe is estimated by using the General Pipe Break Model(GPBM). In order to use the GPBM effectively, improvement of the GPBM is presented in this paper by utilizing additional break data that is the cumulative number of pipe break of 0 for the time of installation and adjusting a value of weighting factor(WF). The residual lives and hazard ratios of the case study pipes of which the cumulative number of pipe breaks is more than one is estimated by using the estimated survival function. It is found that the average residual lives of the steel and cast iron pipes are about 25.1 and 21 years, respectively. The hazard rate of the cast iron pipes is found to be higher than the steel pipes until 20 years since installation. However, the hazard rate of the cast iron pipes become lower than the hazard rates of the steel pipes after 20 years since installation.