Longitudinal observational data on patients can be used to investigate causal effects of time‐varying treatments on time‐to‐event outcomes. Several methods have been developed for estimating such ...effects by controlling for the time‐dependent confounding that typically occurs. The most commonly used is marginal structural models (MSM) estimated using inverse probability of treatment weights (IPTW) (MSM‐IPTW). An alternative, the sequential trials approach, is increasingly popular, and involves creating a sequence of “trials” from new time origins and comparing treatment initiators and non‐initiators. Individuals are censored when they deviate from their treatment assignment at the start of each “trial” (initiator or noninitiator), which is accounted for using inverse probability of censoring weights. The analysis uses data combined across trials. We show that the sequential trials approach can estimate the parameters of a particular MSM. The causal estimand that we focus on is the marginal risk difference between the sustained treatment strategies of “always treat” vs “never treat.” We compare how the sequential trials approach and MSM‐IPTW estimate this estimand, and discuss their assumptions and how data are used differently. The performance of the two approaches is compared in a simulation study. The sequential trials approach, which tends to involve less extreme weights than MSM‐IPTW, results in greater efficiency for estimating the marginal risk difference at most follow‐up times, but this can, in certain scenarios, be reversed at later time points and relies on modelling assumptions. We apply the methods to longitudinal observational data from the UK Cystic Fibrosis Registry to estimate the effect of dornase alfa on survival.
Abstract
Introduction
Assessing objective measures of sleep fragmentation could yield important features reflecting impaired sleep quality in people with insomnia. Survival analysis allows the ...specific examination of the stability of NREM sleep, REM sleep and wake. The objective of this study was to assess the differences between survival dynamics of NREM sleep, REM sleep and wake between people with insomnia and healthy controls.
Methods
We analyzed polysomnography recordings from 88 people with insomnia and 92 healthy controls. For each participant, survival dynamics of REM sleep, NREM sleep and wake were represented using Weibull distributions. We used lasso penalized linear regression to analyze the difference between participant groups with respect to the Weibull scale and shape parameters, while correcting for age, sex, total sleep time and relevant interaction effects. Because comparisons were done for scale and shape parameters of REM sleep, NREM sleep and wake, a Bonferroni correction was applied, resulting in an alpha value of 0.05/6 = 0.0083.
Results
Significant effects of group were found for the NREM scale parameter (unstandardized model coefficient B=-0.79, t=-3.0, p=0.0035), and for the scale and shape parameters of wake (scale parameter B=7.6, t=2.8, p=0.0065; shape parameter B=0.20, t=2.9, p=0.0048). Results indicated that people with insomnia had less stable NREM sleep and more stable wake after sleep onset compared to healthy controls. Additionally, the altered distribution of wake segment lengths indicated an increased difficulty to fall asleep after longer awakenings in the insomnia group. However, these differences were mainly observed in younger participants. Significant effects of group for the survival parameters of REM sleep were not found.
Conclusion
As illustrated by our results, survival analysis can be very useful for disentangling different types of sleep fragmentation in people with insomnia. For instance, the current findings suggest that people with insomnia have an increased fragmentation of NREM sleep, but not necessarily of REM sleep. Additional research into the underlying mechanisms of NREM sleep fragmentation could possibly lead to a better understanding of impaired sleep quality in people with insomnia, and consequently to improved treatment.
Support (if any):
IntroductionDrivers are increasingly studied ablation targets for atrial fibrillation (AF). Focal and rotational activities (FAs/RAs) have been identified in various mapping methods and recent ...meta-analyses suggest that ablation at these sites has both short term and long term efficacy in treating AF. Most of these sites lay remote to the pulmonary veins, which may explain the limited success of pulmonary vein isolation (PVI) ablation alone.PurposeThe main objective was to compare the outcomes, extended to 30-months follow-up period, with regards to freedom from atrial arrythmia after PVI and FAs/RAs ablation vs. standard approach PVI with additional lines as per operator judgement. Secondly, to study the anatomical distribution of FAs/RAs and their frequency across the left atrium (LA) post PVI.MethodsWe conducted a single-centre retrospective observational study of 60 cases with persistent AF, having undergone de novo radiofrequency (RF) ablation by a single operator- 40 patients had standard PVI ablation and 20 had FAs/RAs mapped and subsequently ablated in addition to PVI. Sequential high-density mapping of LA in AF was performed post PVI using validated automated algorithm CARTOFINDER in CARTO 3 (multielectrode catheter applied for 30 seconds at each anatomical location) to detect FAs/RAs. Follow up information post index procedures were collected using electronic hospital records. The primary outcome was freedom from atrial arrythmia identified using Alive Cor remote monitoring, Holter and ECGs. All data were analysed using SPSS software program v.29 and XLSTAT.ResultsBaseline cohort demographics were comparable in both groups, importantly for age, gender and LA size (table 1). The Kaplan Meier survival analysis at the 30-months end-point (figure 1) suggests that trends in maintaining sinus rhythm was superior in those who had FAs/RAs ablated. The log-rank test confirmed that there was statistically significant difference in AF freedom between the two ablation strategies (p=0.035). There was no significant difference in the number of additional ablation lines created in both groups (p=0.54). A total of 279 areas of interest (AOIs) were mapped (average 13.95 applications per patient), with a total of 84 FAs and 3 RAs detected. The left atrial appendage (LAA) hosted the majority (n=35, 41.6%) of FAs/RAs among all 9 segments of LA -anterior (n=15), roof (n=13), floor (n=6), posterior, septal, lateral, RPVA and LPVA (figure 2).Abstract 12 Table 1Demographics of study and control groupsAbstract 12 Figure 1Kaplan Meier survival analysis showing AF freedom at end pointFigure omitted. See PDFAbstract 12 Figure 2Frequency of focal and rotational activities as per anatomical segments of left atriumFigure omitted. See PDFConclusionLong term follow up revealed the addition of FAs/RAs ablation with PVI in persistent AF resulted in significantly lower AF recurrence compared to PVI with additional lines only, both short and long term. Further studies with a larger cohort looking at this innovative technology with such improvement in AF burden is recommended.
NPLs (Non-PerformingLoans), ou Créditos Não Performados são passivos resultantes de créditos inadimplentes. O mercado de compra e venda desse tipo de ativos vem crescendo em território nacional, ...alavancada pela expansão de crédito iniciada em meados de 2003. É de interesse de muitas empresascederem seus passivos em atraso para conseguir recuperar parte de seus recursos, além de eliminar o saldo devedor dos balanços, melhorando seus resultados. O passo inicial para a cessão de carteiras em atraso é estimar seu valor e projetar o montante com potencial de recuperação. Entretanto, existe uma hipótese pouca avaliada pelos investidores: a probabilidade do devedor estar vivo para quitar sua dívida. O objetivo deste artigoé verificar o impacto da probabilidade de sobrevivência do devedor na recuperação de crédito. Os resultados apontam que, ao considerar o fator atuarial de sobrevivência, a estimativa da recuperação tende a cair.
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