Weibull Survival Model Research Articles

Impact of Nonalcoholic Hepatic Steatosis on the Warranty Period of a Coronary Artery Calcium Score of 0: Results From the Multi-Ethnic Study of Atherosclerosis.

For individuals with a coronary artery calcium (CAC) score of 0, CAC rescans at appropriate timings are recommended, depending on individual risk profiles. Although nonalcoholic fatty liver disease, recently redefined as metabolic-associated fatty liver disease, is a risk factor for atherosclerotic cardiovascular disease events, its relationship with the warranty period of a CAC score of 0 has not been elucidated. A total of 1944 subjects from the MESA (Multi-Ethnic Study of Atherosclerosis) with a baseline CAC score of 0, presence or absence of nonalcoholic hepatic steatosis, and at least 1 follow-up computed tomography scan were included. Nonalcoholic hepatic steatosis was defined using nonenhanced computed tomography and liver/spleen attenuation ratio <1. The association between nonalcoholic hepatic steatosis and new CAC incidence (CAC score >0) was evaluated using a Weibull survival model. Nonalcoholic hepatic steatosis was identified in 268 (14%) participants. Participants with nonalcoholic hepatic steatosis had higher CAC incidence than those without nonalcoholic hepatic steatosis. Nonalcoholic hepatic steatosis was independently associated with new CAC incidence after adjustment for atherosclerotic cardiovascular disease risk factors (hazard ratio, 1.28 [95% CI, 1.05-1.57]; P=0.015). Using a 25% testing yield (25% of participants with zero CAC at baseline would be expected to have developed a CAC score >0), the warranty period of a CAC score of 0 in participants with nonalcoholic hepatic steatosis was shorter than in those without nonalcoholic hepatic steatosis (4.7 and 6.3 years). This association was consistent regardless of sex, race/ethnicity, age, and 10-year atherosclerotic cardiovascular disease risk. Nonalcoholic hepatic steatosis had an impact on the warranty period of a CAC score of 0. The study suggests that the time period until a CAC rescan should be shorter in those with nonalcoholic hepatic steatosis and a CAC score of 0.

Association of midlife air pollution exposures and residential road proximity with incident dementia: The Atherosclerosis Risk in Communities (ARIC) study

BackgroundIncreasing evidence links higher air pollution exposures to increased risk of cognitive impairment. While midlife risk factors are often most strongly linked to dementia risk, few studies have considered associations between midlife roadway proximity or ambient air pollution exposure and incident dementia decades later, in late life. ObjectivesOur objective was to determine if midlife exposures to ambient air pollution or roadway proximity are associated with increased risk of dementia in the Atherosclerosis Risk in Communities (ARIC) study over up to 29 years of follow-up. MethodsOur eligible sample included Black and White ARIC participants without dementia at Visit 2 (1990–1992). Participants were followed through Visit 7 (2018–2019), with dementia status and onset date defined based on formal dementia ascertainment at study visits, informant interviews, and surveillance efforts. We used adjusted Weibull survival models to assess the associations of midlife ambient air pollution and road proximity with incident dementia. ResultsThe median age at baseline (1990–1992, Visit 2) of the 12,700 eligible ARIC participants was 57.0 years; 56.0% were female, 24.2% were Black, and 78.9% had at least a high school education. Over up to 29 years of follow-up, 2511 (19.8%) persons developed dementia. No associations were found between ambient air pollutants and proximity to major roadways with risk of incident dementia. In exploratory analyses, living closer to roadways in midlife increased dementia risk in individuals younger at baseline and those without midlife hypertension, and there was evidence of increased risk of dementia with increased midlife exposure to NOx, several PM2.5 components, and trace metals among those with diabetes in midlife. ConclusionsMidlife exposure to ambient air pollution and midlife roadway proximity was not associated with dementia risk over decades of follow-up. Further investigation to explore potential for greater susceptibility among specific subgroups identified here is needed.

Wealth Redistribution to Extend Longevity in the US

The US is unique among wealthy countries in its degree of wealth inequality and its poor health outcomes. Wealth is known to be positively associated with longevity, but little is known about whether wealth redistribution might extend longevity. To examine the association between wealth and longevity and estimate the changes in longevity that could occur with simulated wealth distributions that were perfectly equal, similar to that observed in Japan (among the most equitable of Organisation for Economic Co-operation and Development [OECD] countries), generated by minimum inheritance proposals, and produced by baby bonds proposals. This longitudinal cohort study analyzed the association between wealth and survival among participants in the Health and Retirement Study (1992-2018), a nationally representative panel study of middle-aged and older (≥50 years) community-dwelling, noninstitutionalized US adults. The data analysis was performed between November 15, 2022, and September 24, 2023. Household wealth on study entry, calculated as the sum of all assets minus the value of debts and classified into deciles. Weibull survival models were used to estimate the association between per-person wealth decile and survival, adjusting for age, sex, marital status, household size, and race and ethnicity. Changes in longevity that might occur under alternative wealth distributions were then estimated. The sample included 35 164 participants (mean [SE] age at study entry, 59.1 [0.1] years; 50.1% female and 49.9% male [weighted]). The hazard of death generally decreased with increasing wealth, wherein participants in the highest wealth decile had a hazard ratio of 0.59 for death (95% CI, 0.53-0.66) compared with those in the lowest decile, corresponding to a 13.5-year difference in survival. A simulated wealth distribution of perfect equality would increase populationwide median longevity by 2.2 years (95% CI, 2.2-2.3 years), fully closing the mortality gap between the US and the OECD average. A simulated minimum inheritance proposal would increase populationwide median longevity by 1.7 years; a simulated wealth distribution similar to Japan's would increase populationwide median longevity by 1.2 years; and a simulated baby bonds proposal would increase populationwide median longevity by 1.0 year. These findings suggest that wealth inequality in the US is associated with significant inequities in survival. Wealth redistribution policies may substantially reduce those inequities and increase population longevity.

Development and External Validation of Models to Predict Need for Nursing Home Level of Care in Community-Dwelling Older Adults With Dementia

Most older adults living with dementia ultimately need nursing home level of care (NHLOC). To develop models to predict need for NHLOC among older adults with probable dementia using self-report and proxy reports to aid patients and family with planning and care management. This prognostic study included data from 1998 to 2016 from the Health and Retirement Study (development cohort) and from 2011 to 2019 from the National Health and Aging Trends Study (validation cohort). Participants were community-dwelling adults 65 years and older with probable dementia. Data analysis was conducted between January 2022 and October 2023. Candidate predictors included demographics, behavioral/health factors, functional measures, and chronic conditions. The primary outcome was need for NHLOC defined as (1) 3 or more activities of daily living (ADL) dependencies, (2) 2 or more ADL dependencies and presence of wandering/need for supervision, or (3) needing help with eating. A Weibull survival model incorporating interval censoring and competing risk of death was used. Imputation-stable variable selection was used to develop 2 models: one using proxy responses and another using self-responses. Model performance was assessed by discrimination (integrated area under the receiver operating characteristic curve [iAUC]) and calibration (calibration plots). Of 3327 participants with probable dementia in the Health and Retirement Study, the mean (SD) age was 82.4 (7.4) years and 2301 (survey-weighted 70%) were female. At the end of follow-up, 2107 participants (63.3%) were classified as needing NHLOC. Predictors for both final models included age, baseline ADL and instrumental ADL dependencies, and driving status. The proxy model added body mass index and falls history. The self-respondent model added female sex, incontinence, and date recall. Optimism-corrected iAUC after bootstrap internal validation was 0.72 (95% CI, 0.70-0.75) in the proxy model and 0.64 (95% CI, 0.62-0.66) in the self-respondent model. On external validation in the National Health and Aging Trends Study (n = 1712), iAUC in the proxy and self-respondent models was 0.66 (95% CI, 0.61-0.70) and 0.64 (95% CI, 0.62-0.67), respectively. There was excellent calibration across the range of predicted risk. This prognostic study showed that relatively simple models using self-report or proxy responses can predict need for NHLOC in community-dwelling older adults with probable dementia with moderate discrimination and excellent calibration. These estimates may help guide discussions with patients and families in future care planning.

Untreated cervical intraepithelial neoplasia grade 2 and subsequent risk of cervical cancer: population based cohort study

ObjectiveTo describe the long term risk of cervical cancer in women with untreated (that is, undergoing active surveillance) or immediately treated cervical intraepithelial neoplasia grade 2 (CIN2).DesignNationwide population based historical...

Long-term trends in family level contribution to mortality – Finland 1990-2000

Abstract Background Family is among the most relevant sociodemographic factors influencing the health and well-being of individuals. However, the general contribution of the family context to premature adult mortality is seldom measured, and possible changes in this effect over time have not been quantified in previous studies. Methods The study is based on individual-level register data on the total Finnish population aged 30 years and over. We estimate two-level Weibull survival models with individuals nested in families for six five-year periods between 1990 and 2020 to assess the degree to which the family context contributes to individual differences in mortality. The median hazard ratio (MHR) is used as a summary measure of this general contextual effect. We assess trends separately by sex and age categories and broad cause of death groups, as well as adjust for different individual- and family-level sociodemographic characteristics. Results The preliminary results show that the contribution of the family level to individual mortality risk is substantial. The family effect shows an increasing trend over three decades and is largest among younger individuals aged 30-49. Conclusions The overall relevance of the family context to mortality is considerable and has grown over time. From a public health perspective, policy and interventions should place more importance on family-level influences on health. Key messages • The family context and whom you live with are increasingly important for health and mortality. • Family-oriented health care and services that consider family-level influences should be developed further.

Cost-effectiveness analysis of 7 treatments in metastatic hormone-sensitive prostate cancer: a public-payer perspective.

Recently, several new treatment regimens have been approved for treating metastatic hormone-sensitive prostate cancer, building on androgen deprivation therapy alone. These include docetaxel androgen deprivation therapy, abiraterone acetate-prednisone androgen deprivation therapy, apalutamide androgen deprivation therapy, enzalutamide androgen deprivation therapy, darolutamide-docetaxel androgen deprivation therapy, and abiraterone-prednisone androgen deprivation therapy with docetaxel. There are no validated predictive biomarkers for choosing a specific regimen. The goal of this study was to conduct a health economic outcome evaluation to determine the optimal treatment from the US public sector (Veterans Affairs). We developed a partitioned survival model in which metastatic hormone-sensitive prostate cancer patients transitioned between 3 health states (progression free, progressive disease to castrate resistance state, and death) at monthly intervals based on Weibull survival model estimated from published Kaplan-Meier curves using a Bayesian network meta-analysis of 7 clinical trials (7208 patients). The effectiveness outcome in our model was quality-adjusted life-years (QALYs). Cost input parameters included initial and subsequent treatment costs and costs for terminal care and for managing grade 3 or higher drug-related adverse events and were obtained from the Federal Supply Schedule and published literature. Average 10-year costs ranged from $34 349 (androgen deprivation therapy) to $658 928 (darolutamide-docetaxel androgen deprivation therapy) and mean QALYs ranged from 3.25 (androgen deprivation therapy) to 4.57 (enzalutamide androgen deprivation therapy). Treatment strategies docetaxel androgen deprivation therapy, enzalutamide androgen deprivation therapy docetaxel, apalutamide androgen deprivation therapy, and darolutamide-docetaxel androgen deprivation therapy were eliminated because of dominance (ie, they were more costly and less effective than other strategies). Of the remaining strategies, abiraterone acetate-prednisone androgen deprivation therapy was the most cost-effective strategy at a willingness-to-pay threshold of $100 000/QALY (incremental cost-effectiveness ratios = $21 247/QALY). Our simulation model found abiraterone acetate-prednisone androgen deprivation therapy to be an optimal first-line treatment for metastatic hormone-sensitive prostate cancer from a public (Veterans Affairs) payer perspective.

Development of an Injury Risk Function for the Anterior Pelvis Under Frontal Lap Belt Loading Conditions.

Iliac wing fractures due to lap belt loading have been identified in laboratory tests for almost 50years and an analysis of recent data suggests these injuries are also occurring in the field. With the introduction of highly autonomous vehicles on the horizon, vehicle manufacturers are exploring open cabin concepts that permit reclined postures and separation of the occupant from the knee bolster and instrument panel. This will result in greater reliance on the lap belt and lap belt/pelvis loading to restrain occupants. No injury criteria exist for iliac wing fractures resulting from lap belt loading like that seen in frontal crash conditions. This study tested the tolerance of isolated iliac wings in a controlled lap belt-like loading environment while incorporating the effect of loading angle after analyzing lap belt loading experiments from a previous study. Twenty-two iliac wings were tested; nineteen of them sustained fracture (exact), but the loading input was insufficient to cause fracture in the other three (right censored). The fracture tolerance of the tested specimens ranged widely (1463-8895 N) and averaged 4091 N (SD 2381 N). Injury risk functions were created by fitting Weibull survival models to data that integrated censored and exact failure observations.

Immigrant generation status and its association with pubertal timing and tempo among Hispanic girls and boys.

In the United States, Hispanic-Latino children reach puberty earlier on average than non-Hispanic white children. Yet among U.S. Hispanic/Latino children, pubertal timing comparisons between immigrant generations have not been made, hence we examined whether pubertal timing differs by immigrant generational status, independent of BMI and acculturation measures. Cross-sectional data on 724 boys and 735 girls, aged 10-15 years, from the Hispanic Community Children's Health Study/Study of Latino (SOL) Youth, were used to predict the median ages of thelarche, pubarche, and menarche in girls, and pubarche and voice change in boys, using Weibull survival models, while adjusting for SOL center, BMI, and acculturation. In girls, the first generation began thelarche earlier than second and third generations (median age [years] [95% confidence interval]: 7.4 [6.1, 8.8] vs. 8.5 [7.3, 9.7] and 9.1 [7.6, 10.7], respectively), but began menarche later (12.9 [12.0,137] vs. 11.8 [11.0, 12.5] and 11.6 [10.6, 12.6], respectively). Pubertal timing and tempo for boys did not differ by generational status. First-generation U.S. Hispanic/Latino girls had the earliest thelarche, latest menarche and longest pubertal tempo, compared to second and third generations. Factors beyond BMI and acculturation may account for the differences in pubertal timing by generational status of U.S. Hispanic/Latino girls.

Complete prevalence and indicators of cancer cure: enhanced methods and validation in Italian population-based cancer registries.

To describe the procedures to derive complete prevalence and several indicators of cancer cure from population-based cancer registries. Cancer registry data (47% of the Italian population) were used to calculate limited duration prevalence for 62 cancer types by sex and registry. The incidence and survival models, needed to calculate the completeness index (R) and complete prevalence, were evaluated by likelihood ratio tests and by visual comparison. A sensitivity analysis was conducted to explore the effect on the complete prevalence of using different R indexes. Mixture cure models were used to estimate net survival (NS); life expectancy of fatal (LEF) cases; cure fraction (CF); time to cure (TTC); cure prevalence, prevalent patients who were not at risk of dying as a result of cancer; and already cured patients, those living longer than TTC at a specific point in time. CF was also compared with long-term NS since, for patients diagnosed after a certain age, CF (representing asymptotical values of NS) is reached far beyond the patient's life expectancy. For the most frequent cancer types, the Weibull survival model stratified by sex and age showed a very good fit with observed survival. For men diagnosed with any cancer type at age 65-74 years, CF was 41%, while the NS was 49% until age 100 and 50% until age 90. In women, similar differences emerged for patients with any cancer type or with breast cancer. Among patients alive in 2018 with colorectal cancer at age 55-64 years, 48% were already cured (had reached their specific TTC), while the cure prevalence (lifelong probability to be cured from cancer) was 89%. Cure prevalence became 97.5% (2.5% will die because of their neoplasm) for patients alive >5 years after diagnosis. This study represents an addition to the current knowledge on the topic providing a detailed description of available indicators of prevalence and cancer cure, highlighting the links among them, and illustrating their interpretation. Indicators may be relevant for patients and clinical practice; they are unambiguously defined, measurable, and reproducible in different countries where population-based cancer registries are active.

Cost-effectiveness analysis (CEA) of seven treatment regimens in metastatic hormone-sensitive prostate cancer (mHSPC): A public payer perspective using network meta-analysis.

5081 Background: Recently several new drug treatment regimens have been approved in mHSPC state, building on using androgen deprivation therapy (ADT) alone. These include docetaxel + ADT (DA), Abiraterone Acetate + Prednisone + ADT (AAP), Apalutamide + ADT (AAT), Enzalutamide + ADT (ET), Darolutamide + Docetaxel + ADT (DAD) and AAP + ADT + Docetaxel (AAD). At present, there are no predictive biomarkers for choosing a specific drug regimen over the other. The goal of this study was to conduct an economic evaluation of FDA-approved standard of care drug regimens in the current management of mHSPC state to determine a cost-effective optimal treatment from the US public sector (Veterans Affairs-VA) perspective with a 10-year time horizon. Methods: We developed a partitioned survival model in which mHSPC patients (pts) transitioned between three health states (progression free, progressive disease to castrate resistance state, and death) at monthly intervals based on Weibull survival model estimated from published Kaplan-Meier curves using a network meta-analysis. A Bayesian network meta-analysis of seven randomized clinical trials included 7,208 mHSPC pts. The effectiveness outcome in our model was quality-adjusted life-years (QALYs) with utility values obtained from published literature. Costs in our model included those associated with treatment regimens, subsequent therapies, terminal care, and for managing grade 3-4 drug related adverse events. Costs were obtained from the Federal Supply Schedule and published literature. Incremental cost-effectiveness ratios (ICERs) were calculated for nondominated treatments. Results: Average 10-year costs ranged from $32,697 (ADT) to $649,622 (DAD). Mean QALYs ranged from 3.25 (ADT) to 4.57 (ET). Treatment with DAT, EAD, and DAD were eliminated due to dominance (i.e. they were more costly and less effective than other treatments). AAT was the most cost-effective strategy at a willingness-to-pay threshold of $100,000/QALY (ICER = $70,150/QALY). Results from our analysis for all regimens are shown. Conclusions: Our CEA simulation model found AAT is an optimal cost-effective first-line treatment strategy in mHSPC state from a public (VA) payer perspective. [Table: see text]

Are psychosocial work factors and work-home interference associated with time to first full return-to-work after sick leave due to common mental disorders?

ObjectiveTo (1) examine the time to first full return-to-work (RTW), and (2) investigate whether psychosocial work factors and work-home interference are associated with time to first full RTW after sick leave due to common mental disorders (CMDs).MethodsThe cohort study comprised 162 employees on sick leave due to CMDs participating in a two-armed cluster-randomised controlled trial in Sweden. Baseline data consisted of a web-based questionnaire and follow-up data of repeated text messages every fourth week for 12 months. The time to first full RTW was estimated using the Kaplan–Meier Estimator. Parametric Weibull survival models with interval-censored outcomes were used to determine associations between psychosocial work factors and work-home interference with time to first full RTW. In a post hoc analysis, time-interval differences in associations for 0– ≤ 6- versus > 6–12 months were tested.ResultsDuring the 12-month follow-up, n = 131 (80.9%) reported a first full RTW. The median time to this RTW was 16 weeks (95% CI 12; 20). High psychological job demands, high emotional job demands, high work-to-home interference (WHI), and low social job support were independently associated with a longer time to first full RTW. Time-interval differences were found for job control and emotional job demands.ConclusionsPsychosocial work demands and WHI are associated with a longer time to RTW after sick leave due to CMDs. Work organisations and rehabilitation practices should include accommodations for high psychological and emotional job demands during RTW, as well as pay attention to the risk of spill-over of high job demands into employees’ private lives.

Timing of Unplanned Reoperation After Lower Extremity Free Flap Reconstruction: What Are the Roles of Procedure Indication and Defect Etiology?

Advancements in lower extremity (LE) microsurgery have allowed for the expansion of indications for LE reconstructions. This project aims to better understand the temporal pattern and risk factors associated with LE free flap failure based on the clinical indication. We analyzed all patients undergoing LE free flap reconstruction from the American College of Surgeons National Surgical Quality Improvement Program 2012-2019 prospectively collected data to determine rates and timing of reoperation. Free flaps were stratified by indication, type, and timing of reoperation. Weibull survival models were used to compare rates of takebacks among time intervals. Multivariable logistic regression was used to identify independent predictors for unplanned reoperation. Four hundred seven of LE free flaps were analyzed. There was a 14.5% rate (59/407) of unplanned reoperation within the first 30 postoperative days (PODs) after surgery. When stratified by the indication necessitating reoperation, patients with an underlying vascular indication had the highest rate of reoperation (40.9%). The reoperation rates were significantly different between indications (P < 0.05) The mean daily proportion of patients experiencing reoperation was highest during POD 0 to 2 (1.47% reoperations per day), which dropped significantly during POD 3 to 10 (0.55% per day) and again during POD 11 to 30 (0.28% per day, P < 0.05). African American race as well as malignant, prosthetic/implant, and wound/infectious indications were significant independent predictors for unplanned reoperation. Lower extremity reconstruction is an important reconstructive option for the coverage of a myriad of defects. Understanding the differences between postoperative reoperation timelines among indication subtypes is important for updated flap monitoring protocols, optimizing ERAS pathways, and beginning dangle protocols.

Cost-effectiveness analysis of seven treatment regimens in metastatic hormone-sensitive prostate cancer (mHSPC): A public payer perspective using network meta-analysis.

268 Background: Recently several new treatment regimens have been approved for treating mHSPC, building on the previous standard of care using androgen deprivation therapy (ADT) alone. These include docetaxel+ADT (DA), Abiraterone Acetate+Prednisone+ADT (AAP), Apalutamide+ADT (AAT), Enzalutamide+ADT (ET), Darolutamide+Docetaxel+ADT (DAD) and Abiraterone+Prednisone+ADT+Docetaxel (AAD). There are no current predictive biomarkers for choosing any specific regimen. The goal of this study was to determine the cost-effectiveness of these new treatments from the US public sector perspective with a lifetime horizon. Methods: We developed a partitioned survival model in which mHSPC patients transitioned between three health states (progression free, progressive disease to castrate resistance state, and death) at monthly intervals based on Weibull survival model estimated from published Kaplan-Meier curves using a network meta-analysis. A Bayesian network meta-analysis of seven clinical trials included 7,208 patients. The effectiveness outcome in our model was quality-adjusted life-years (QALYs) with utility values obtained from published literature. Costs in our model included those associated with treatment regimens and subsequent therapies, terminal care, and for managing grade 3-4 drug related adverse events, and were obtained from the Federal Supply Schedule and published literature. Results: Average lifetime costs ranged from $154,139 (AAP) to $770,848 (DAD) and mean QALYs ranged from 3.33 (ADT) to 5.08 (ET). All treatment strategies other than AAP and ET were eliminated due to dominance. Compared to AAP, the incremental cost-effectiveness ratio for ET was $484,943/QALY. Results from our analysis including all regimens are shown. Conclusions: Our simulation model found that ET in mHSPC state yielded the most QALYs and would be the most cost-effective option with a WTP threshold as high as $500,000/QALY. However, for a WTP threshold of $150,000/QALY, AAP was the most cost-effective treatment strategy. [Table: see text]

Human Lumbar Spine Injury Risk in Dynamic Combined Compression and Flexion Loading.

Anticipating changes to vehicle interiors with future automated driving systems, the automobile industry recently has focused attention on crash response in novel postures with increased seatback recline. Prior research found that this posture may result in greater risk of lumbar spine injury in the event of a frontal crash. This study developed a lumbar spine injury risk function (IRF) that estimated injury risk as a function of simultaneously applied compression force and flexion moment. Force and moment failure data from 40 compression-flexion tests were utilized in a Weibull survival model, including appropriate data censoring. A mechanics-based injury metric was formulated, where lumbar spine compression force and flexion moment were normalized by specimen geometry. Subject age was incorporated as a covariate to further improve model fit. A weighting factor was included to adjust the influence of force and moment, and parameter optimization yielded a value of 0.11. Thus, the normalized compression force component had a greater effect on injury risk than the normalized flexion moment component. Additionally, as force was nominally increased, less moment was required to produce injury for a given age and specimen geometry. The resulting IRF may be utilized to improve occupant safety in the future.

Weibull Regression Model on Hospitalization Time Data of COVID-19 Patients at Abdul Wahab Sjahranie Hospital Samarinda

The Weibull regression model is a Weibull distribution that is directly influenced by covariates. The Weibull regression model discussed in this study was the Weibull survival and the Weibull hazard regression model. The Weibull regression model in this study was applied to the hospitalization time data of COVID-19 patients from May to September 2021 at the RSUD Abdul Wahab Sjahranie Samarinda. The event of the study is recovery of patient. This study aims to obtain Weibull survival and hazard regression model to the hospitalization time data of Covid-19 patients, to obtain the factors that affect the chance of not recovering (survive) and the recovery rate of Covid-19 patients, and also to interpret Weibull survival and hazard regression models based on the obtained model. In this study, the Maximum Likelihood Estimation (MLE) was used as the parameter estimation method. The closed form of the Maximum Likelihood (ML) estimator cannot be found analytically, and the approximation of ML estimator was found using Newton-Raphson iterative method. Based on the test results, the factors that influence the chance of not recovering and the recovery rate of COVID-19 patients were comorbidities history. The chance of not not recovering (survive) for patients who have a history of comorbidities is greater than the chance of not recovering (survive) for patients who have no history of comorbidities. The recovery rate for COVID-19 patients who have a history of comorbidities is 0,5358 times the recovery rate for patients without a history of comorbidities.

Distribution of Computerized Datasets To Fit Weibull, Log-Logistics and Gompertz Survival Models

The lack of detailed and analytic study on the risk factors of Breast cancer in Nigerian presents us with the challenge of not knowing the risk factors distinct to the Nigerian settings. Effectively handling the breast cancer treatment in co-infected patients is delicate. Some challenges to the treatment of breast cancer infection include drug-to-drug interactions between procedures required to treat the cancer cells, thus the hormonal drugs burdens patient’s inability to comply with dosage intake thereby making women with breast cancer prone to developing other forms of cancer. The aim of the research was to analyzed distributed dataset to fit Weibull, Log-logistics and Gompertz survival models. The research methodology involved the collection of data cases on oncological study analyzed using descriptive statistics and parametric survival models. The result shows that the Cramer-von Misses (W), the Anderson Darling (A) and the Kolmogorov Smirnov (D) statistics, Log-logistic distribution has greater p-value than other distributions, hence it is the best fit for survival times of a group of patients given chemotherapy treatment. The research concluded that Gompertz model was the best fitted model to survival times of a group of patients given chemotherapy treatment data, while log-logistic distribution was the best fit distribution for the data. It also concluded that Weibull and log-logistic models perform better than Gompertz model in fatigue fracture data, while log-logistic distribution was the best fit for the data and Gompertz model and the distribution was the best fit to nicotine measurements.

Comparing the Performance of a Survival Models In a Computerized Dataset

Every patient demonstrates the loss of one year of healthy life. In addition, 7.6% of global DALYs are assigned to the neoplasms. The three leading cancers in both sexes worldwide were lung cancer (13% of the total), breast cancer (11.9%), and colorectal cancer (9.7%); the most common types of cancer in men, respectively, are lung cancer (16.8%), prostate cancer (14.8%) and colorectal cancer (10.1%) while in women they are ordered as breast cancer (25.1%), colorectal cancer (9.2%) and lung cancer (8.8%). The research aimed to compare the performance of Weibull, Log-logistics, and Gompertz survival models on oncological data. The research methodology involved the collection of data cases on oncological study analyzed using descriptive statistics, parametric survival models were also used in the analysis. The result shows the maximum likelihood estimates of dataset 1 with 3 with a different model fit, all the information criteria and log-likelihood of the models indicate that Gompertz model has the smallest value in all the information criteria, indicating that Gompertz model is the best-fitted model to Remission Times of Bladder Cancer patient’s data. The research concludes that a parametric that can best be used to model cancer data known as Gompertz model is the best-used model in the research. The research will enable other researchers such as medical personnel to model or know the best model for cancer-related cases.

Critical Importance of the First Postoperative Days After Head and Neck Free Flap Reconstruction: An Analysis of Timing of Reoperation Using the National Surgical Quality Improvement Program Database.

Head and neck free flaps remain associated with considerable rates of take-back and prolonged hospital length of stay. However, there have been no studies on a national level benchmarking the timeline and predictors of head and neck free flap take-back. Patients undergoing head and neck free flap reconstruction from the American College of Surgeons National Surgical Quality Improvement Program 2012-2019 database were analyzed to determine the rates of take-back. Timing and rates of unplanned head and neck free flap take-backs were stratified by tissue type and postoperative day (POD) over the first month. Weibull survival models were used to compare rates of take-backs among time intervals. Multivariable logistic regression was used to identify the independent predictors of take-back. Three thousand nine hundred six head and neck free flaps were analyzed. The mean daily proportion of patients experiencing take-back during PODs 0 to 1 was 0.95%; this dropped significantly to a mean daily proportion of 0.54% during POD 2 (P < 0.01). In addition, there were significant drops in take-back when comparing POD 2 (0.54%) to POD 3 (0.26%) and also when comparing POD 4 (0.20%) with PODs 5 to 30 (0.032% per day) (P < 0.05). The soft tissue and osseous flap populations demonstrated a similar trend in unplanned take-back. This is the first national study to specifically analyze the timing of take-back in the head and neck reconstruction population. These data highlight the importance of flap monitoring during the first 5 PODs, with ERAS pathway optimization aiming for discharge by the end of the first postoperative week.

Cost-effectiveness analysis of olaparib as maintenance therapy in patients with platinum-sensitive relapsed ovarian cancer and a BRCA1/2 mutation in china.

Objective: The aim of this study was to investigate the cost-effectiveness of olaparib as the maintenance therapy in patients with platinum-sensitive relapsed ovarian cancer and a BRCA1/2 mutation in China. Methods: A Markov model was developed to simulate the clinical course of typical patients with ovarian cancer in the SOLO2 trial. The Weibull survival model was employed to fit the Kaplan–Meier progression-free survival and overall survival probabilities of the olaparib and placebo strategies, respectively. The clinical and direct costs data were derived from randomized clinical trials and published reports. Quality-adjusted life-years (QALYs) and incremental cost-effectiveness ratios (ICERs) were estimated over a 10-year lifetime horizon. Meanwhile, one-way and probabilistic sensitivity analyses were used to explore the impact of uncertainty on the model’s outcomes. Results: Overall, the incremental effectiveness and cost of olaparib versus placebo were 0.56 QALYs and $43,292.92, respectively, resulting in an ICER of $77,620.56/QALY, higher than the willingness-to-pay (WTP) threshold of China ($31,498.70/QALY). The results were sensitive to the cost of olaparib and utility of PFS. Scenario analyses suggested that when the cost of olaparib was reduced by 60%, ICER decreased to $30,611.52/QALY, lower than the WTP threshold of China. Conclusion: The findings from the present analysis suggest that olaparib with a 60% discount as maintenance therapy might be cost effective in patients with platinum-sensitive relapsed ovarian cancer and a BRCA1/2 mutation in China.