Cox regression of clustered event times with covariates missing not at random

2019 ◽  
Vol 46 (4) ◽  
pp. 1315-1346 ◽  
Author(s):  
Li Liu ◽  
Yanyan Liu ◽  
Yi Xiong ◽  
X. Joan Hu
Keyword(s):  
Cox Regression ◽  
Missing Not At Random ◽  
Event Times

Imputing missing time-dependent covariate values for the discrete time Cox model

2019 ◽  
Vol 29 (8) ◽  
pp. 2074-2086
Author(s):  
Havi Murad ◽  
Rachel Dankner ◽  
Alla Berlin ◽  
Liraz Olmer ◽  
Laurence S Freedman
Keyword(s):  
Discrete Time ◽  
Missing Values ◽  
Cox Regression ◽  
Cox Model ◽  
Missing At Random ◽  
Time Dependent ◽  
Outcome Variable ◽  
Sequential Approach ◽  
Random Patterns ◽  
Event Times

We describe a procedure for imputing missing values of time-dependent covariates in a discrete time Cox model using the chained equations method. The procedure multiply imputes the missing values for each time-period in a time-sequential manner, using covariates from the current and previous time-periods as well as the survival outcome. The form of the outcome variable used in the imputation model depends on the functional form of the time-dependent covariate(s) and differs from the case of Cox regression with only baseline covariates. This time-sequential approach provides an approximation to a fully conditional approach. We illustrate the procedure with data on diabetics, evaluating the association of their glucose control with the risk of selected cancers. Using simulations we show that the suggested estimator performed well (in terms of bias and coverage) for completely missing at random, missing at random and moderate non-missing-at-random patterns. However, for very strong non-missing-at-random patterns, the estimator was seriously biased and the coverage was too low. The procedure can be implemented using multiple imputation with the Fully conditional Specification (FCS) method (MI procedure in SAS with FCS statement or similar packages in other software, e.g. MICE in R). For use with event times on a continuous scale, the events would need to be grouped into time-intervals.

scholarly journals Cox Regression with Covariates Missing Not at Random

2010 ◽  
Vol 3 (2) ◽  
pp. 208-222 ◽  
Author(s):  
Victoria J. Cook ◽  
X. Joan Hu ◽  
Tim B. Swartz
Keyword(s):  
Cox Regression ◽  
Missing Not At Random

Prospective Analysis of Factors Related to Migraine Attacks: The PAMINA Study

Cephalalgia ◽  
2007 ◽  
Vol 27 (4) ◽  
pp. 304-314 ◽  
Author(s):  
C Wöber ◽  
W Brannath ◽  
K Schmidt ◽  
M Kapitan ◽  
E Rudel ◽  
...  
Keyword(s):  
Cox Regression ◽  
Meteorological Factors ◽  
Wide Spectrum ◽  
Muscle Tension ◽  
P Value ◽  
Prospective Analysis ◽  
Regression Analyses ◽  
Headache Onset ◽  
Dichotomous Variables ◽  
Event Times

Migraine is related to numerous factors such as hormones, stress or nutrition, but information about their actual importance is limited. Therefore, we analysed prospectively a wide spectrum of factors related to headache in migraineurs. We examined 327 migraineurs recruited via newspapers who kept a comprehensive diary for 3 months. Statistical analysis comprising 28 325 patient days and 116 dichotomous variables was based on the interval between two successive headache attacks. We calculated univariate Cox regression analyses and included covariables with a P-value of <0.05 in two stepwise multivariate Cox regression analyses, the first accounting for a correlation of the event times within a subject, the second stratified by the number of headache-free intervals. We performed similar analyses for the occurrence of migraine attacks and for the persistence of headache and migraine. Menstruation had the most prominent effect, increasing the hazard of occurrence or persistence of headache and migraine by up to 96%. All other factors changed the hazard by <35%. The two days before menstruation and muscle tension in the neck, psychic tension, tiredness, noise and odours on days before headache onset increased the hazard of headache or migraine, whereas days off, a divorced marriage, relaxation after stress, and consumption of beer decreased the hazard. In addition, three meteorological factors increased and two others decreased the hazard. In conclusion, menstruation is most important in increasing the risk of occurrence and persistence of headache and migraine. Other factors increase the risk less markedly or decrease the risk.

Predictive Model for Live Birth at 12 Months After Starting In-Vitro Fertilization Treatment

MedPharmRes ◽  
2018 ◽  
Vol 2 (2) ◽  
pp. 5-20
Author(s):  
Vu Ho ◽  
Toan Pham ◽  
Tuong Ho ◽  
Lan Vuong
Keyword(s):  
In Vitro Fertilization ◽  
Live Birth ◽  
Cox Regression ◽  
Financial Burden ◽  
Oocyte Retrieval ◽  
Operating Characteristics ◽  
Vitro Fertilization ◽  
Cox Regression Analysis ◽  
Significant Difference

IVF carries a considerable physical, emotional and financial burden. Therefore, it would be useful to be able to predict the likelihood of success for each couple. The aim of this retrospective cohort study was to develop a prediction model to estimate the probability of a live birth at 12 months after one completed IVF cycle (all fresh and frozen embryo transfers from the same oocyte retrieval). We analyzed data collected from 2600 women undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) at a single center in Vietnam between April 2014 and December 2015. All patients received gonadotropin-releasing hormone (GnRH) antagonist stimulation, followed by fresh and/or frozen embryo transfer (FET) on Day 3. Using Cox regression analysis, five predictive factors were identified: female age, total dose of recombinant follicle stimulating hormone used, type of trigger, fresh or FET during the first transfer, and number of subsequent FET after the first transfer. The area under the receiver operating characteristics curve for the final model was 0.63 (95% confidence interval [CI] 0.60‒0.65) and 0.60 (95% CI 0.57‒0.63) for the validation cohort. There was no significant difference between the predicted and observed probabilities of live birth (Hosmer-Lemeshow test, p > 0.05). The model developed had similar discrimination to existing models and could be implemented in clinical practice.

Obesitas Umum Berdasarkan Indeks Masa Tubuh Dan Obesitas Abdominal Berdasarkan Lingkar Pinggang Terhadap Kejadian Prediabetes

2018 ◽  
Vol 16 (3) ◽  
pp. 34-41
Author(s):  
Nur Rizky Ramadhani ◽  
Nurhayati Adnan
Keyword(s):  
Cox Regression

Prediabetes adalah masalah kesehatan global. Prevalensi prediabetes meningkat signiikan di seluruh dunia dan umumnya tinggi di masyarakat serta merupakan keadaan risiko tinggi untuk DM. Obesitas memiliki peranan penting dalam patoisiologi prediabetes. Penelitian ini bertujuan untuk mengetahui apakah obesitas umum dan obesitas abdominal secara bersama-sama berhubungan terhadap kejadian prediabetes pada kelompok usia 20-65 tahun di Kecamatan Bogor Tengah berdasarkan faktor riwayat DM keluarga, jenis kelamin, umur, merokok, hipertensi, aktiitas isik dan stress. Desain studi yang digunakan adalah potong lintang dengan Cox Regression untuk analisis multivariable. Data analisis merupakan data baseline dari studi kohort faktor risiko penyakit tidak menular tahun 2012. Ada 3244 responden yang dipilih dengan teknik sampel acak. Hasil analisis menunjukkan bahwa obesitas terhadap kejadian prediabetes setelah mengendalikan faktor umur adalah obesitas umum PR 1,56 (95% CI: 1,15-2,11), obesitas abdominal PR 1,43 (95% CI; 1,09-1,85) dan obesitas umum dan obesitas abdominal secara bersama-sama PR 1,93 (95% CI; 1,62-2,28). Untuk itu, obesitas umum dan obesitas abdominal secara bersama-sama berkontribusi paling besar terhadap peningkatan prevalensi prediabetes. Peningkatan kesadaran dan skrining prediabetes pada kelompok risiko tinggi berdasarkan pengukuran IMT bersama dengan lingkar pinggang penting untuk dipertimbangkan sebagai bagian dari upaya untuk mengurangi epidemi prediabetes di masyarakat. Kata Kunci: obesitas abdominal, obesitas umum, prediabetes

Does Hospitalization Predict the Disease Course in Ulcerative Colitis? Prevalence and Predictors of Hospitalization and Re- Hospitalization in Ulcerative Colitis in a Population-based Inception Cohort (2000-2012)

2015 ◽  
Vol 24 (3) ◽  
pp. 287-292 ◽  
Author(s):  
Petra A. Golovics ◽  
Laszlo Lakatos ◽  
Michael D. Mandel ◽  
Barbara D. Lovasz ◽  
Zsuzsanna Vegh ◽  
...  
Keyword(s):  
Ulcerative Colitis ◽  
Cox Regression ◽  
Diagnostic Procedures ◽  
Population Based ◽  
Disease Course ◽  
Inception Cohort ◽  
Disease Extent ◽  
Cox Regression Analysis ◽  
Hospitalization Rates

Background & Aims: Limited data are available on the hospitalization rates in population-based studies. Since this is a very important outcome measure, the aim of this study was to analyze prospectively if early hospitalization is associated with the later disease course as well as to determine the prevalence and predictors of hospitalization and re-hospitalization in the population-based ulcerative colitis (UC) inception cohort in the Veszprem province database between 2000 and 2012. Methods: Data of 347 incident UC patients diagnosed between January 1, 2000 and December 31, 2010 were analyzed (M/F: 200/147, median age at diagnosis: 36, IQR: 26-50 years, follow-up duration: 7, IQR 4-10 years). Both in- and outpatient records were collected and comprehensively reviewed. Results: Probabilities of first UC-related hospitalization were 28.6%, 53.7% and 66.2% and of first re-hospitalization were 23.7%, 55.8% and 74.6% after 1-, 5- and 10- years of follow-up, respectively. Main UC-related causes for first hospitalization were diagnostic procedures (26.7%), disease activity (22.4%) or UC-related surgery (4.8%), but a significant percentage was unrelated to IBD (44.8%). In Kaplan-Meier and Cox-regression analysis disease extent at diagnosis (HR extensive: 1.79, p=0.02) or at last follow-up (HR: 1.56, p=0.001), need for steroids (HR: 1.98, p<0.001), azathioprine (HR: 1.55, p=0.038) and anti-TNF (HR: 2.28, p<0.001) were associated with the risk of UC-related hospitalization. Early hospitalization was not associated with a specific disease phenotype or outcome; however, 46.2% of all colectomies were performed in the year of diagnosis. Conclusion: Hospitalization and re-hospitalization rates were relatively high in this population-based UC cohort. Early hospitalization was not predictive for the later disease course.

The impact of statin therapy after surgical or endovascular treatment of cerebral aneurysms

2020 ◽  
Vol 133 (1) ◽  
pp. 182-189
Author(s):  
Tae-Jin Song ◽  
Seung-Hun Oh ◽  
Jinkwon Kim
Keyword(s):  
Statin Therapy ◽  
Coil Embolization ◽  
Primary Outcome ◽  
Cox Regression ◽  
Cerebral Aneurysms ◽  
Time Dependent ◽  
Lipid Lowering ◽  
Surgical Clipping ◽  
The Impact

OBJECTIVECerebral aneurysms represent the most common cause of spontaneous subarachnoid hemorrhage. Statins are lipid-lowering agents that may expert multiple pleiotropic vascular protective effects. The authors hypothesized that statin therapy after coil embolization or surgical clipping of cerebral aneurysms might improve clinical outcomes.METHODSThis was a retrospective cohort study using the National Health Insurance Service–National Sample Cohort Database in Korea. Patients who underwent coil embolization or surgical clipping for cerebral aneurysm between 2002 and 2013 were included. Based on prescription claims, the authors calculated the proportion of days covered (PDC) by statins during follow-up as a marker of statin therapy. The primary outcome was a composite of the development of stroke, myocardial infarction, and all-cause death. Multivariate time-dependent Cox regression analyses were performed.RESULTSA total of 1381 patients who underwent coil embolization (n = 542) or surgical clipping (n = 839) of cerebral aneurysms were included in this study. During the mean (± SD) follow-up period of 3.83 ± 3.35 years, 335 (24.3%) patients experienced the primary outcome. Adjustments were performed for sex, age (as a continuous variable), treatment modality, aneurysm rupture status (ruptured or unruptured aneurysm), hypertension, diabetes mellitus, household income level, and prior history of ischemic stroke or intracerebral hemorrhage as time-independent variables and statin therapy during follow-up as a time-dependent variable. Consistent statin therapy (PDC > 80%) was significantly associated with a lower risk of the primary outcome (adjusted hazard ratio 0.34, 95% CI 0.14–0.85).CONCLUSIONSConsistent statin therapy was significantly associated with better prognosis after coil embolization or surgical clipping of cerebral aneurysms.

RESULTS OF TREATMENT OF LOCALLY RECURRING SOFT TISSUES SARCOMAS OF EXTREMITIES

2018 ◽  
Vol 64 (3) ◽  
pp. 408-413
Author(s):  
Grigoriy Zinovev ◽  
Georgiy Gafton ◽  
Sergey Novikov ◽  
Ivan Gafton ◽  
Yekaterina Busko ◽  
...  
Keyword(s):  
Radiation Therapy ◽  
Soft Tissues ◽  
Cox Regression ◽  
Disease Free Survival ◽  
Tumor Location ◽  
Long Term Results ◽  
Clinical Feature ◽  
National Medical ◽  
Results Of Treatment ◽  
Kaplan Meier

Background: The most striking clinical feature of soft tissues sarcomas (STS) is their ability to recur. At present disputes about the clinical and morphological factors of STS recurrence such as the degree of malignancy, size, location, depth of tumor location, patient’s age and the presence of previous relapses in the anamnesis do not subside. It also requires clarification of the effect of the volume of tissues removed on the long-term results of treatment of STS as well as indications for the application of various regimes of remote radiation therapy. Materials and methods: Of 1802 registered cases of STS of extremities at the N.N. Petrov National Medical Research Center of Oncology from 2004 to 2016 there were selected data on 213 patients who suffered from at least one relapse of the disease. There was performed an assessment of overall, non-metastatic and disease-free survival using a single-factor (the Kaplan-Meier method) and multivariate analysis (the Cox regression model). Conclusion: The detection of various prognostic factors of locally recurrent STS allows determining the necessary treatment tactics (the vastness and traumatism of surgery and the advisability of radiation therapy).

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