A Practical Overview and Reporting Strategies for Statistical Analysis of Survival Studies

Letter: Allostatic Load and Adverse Prognosis in Inflammatory Bowel Disease-Need More Evidence. Authors' Reply

This article is linked to Zhao et al papers. To view these articles, visit https://doi.org/10.1111/apt.18217 and https://doi.org/10.1111/apt.18249.

Role of cardiovascular health factors in mediating social inequalities in the incidence of dementia in the UK: two prospective, population-based cohort studies

Background

The contribution of modifiable risk factors to social inequalities in dementia, observed in longitudinal studies, remains unclear. We aimed to quantify the role of cardiovascular health factors, assessed using Life's Essential 8 (LE8) score, in mediating social inequalities in incidence of dementia and, for comparison, in incidence of stroke, coronary heart disease, and mortality.

Methods

In this prospective, population-based cohort study, we collected data from the UK Whitehall II Study and UK Biobank databases. Participants were included if data were available on SEP, outcomes and LE8 (smoking, physical activity, diet, body mass index, blood pressure, fasting blood glucose, lipid levels, sleep duration). The primary outcome was incident dementia and secondary outcomes were stroke, coronary heart disease, and mortality. Outcomes were derived from electronic healthcare records. Socioeconomic position (SEP) was measured by occupation in Whitehall II and education in UK Biobank. Counterfactual mediation analysis was used to quantify the extent to which LE8 score explained the associations of SEP with all outcomes. Analyses involved Cox regression, accelerated failure time models, and linear regression; and were adjusted for age, sex, and ethnicity.

Findings

Between 10.09.1985 and 29.03.1988, a total of 9688 participants (mean age ± SD 44.9 ± 6.0; 67% men) from the Whitehall II study, and between 19.12.2006 and 01.10.2010, 278,215 participants (mean age ± SD 56.0 ± 8.1; 47% men) from the UK Biobank were included. There were 606 and 4649 incident dementia cases over a median (interquartile range) follow-up of 31.7 (31.1-32.7) and 13.5 (12.7-14.1) years respectively in Whitehall II and UK Biobank. In Whitehall II, the hazard ratio was 1.85 [95% CI 1.42, 2.32] for the total effect of SEP on dementia and 1.20 [1.12, 1.28] for the indirect effect via the LE8, the proportion mediated being 36%. In UK Biobank, the total effect of SEP on dementia was 1.65 [1.54, 1.78]; the indirect effect was 1.11 [1.09, 1.12], and the proportion mediated was 24%. The proportions mediated for stroke, coronary heart disease, and mortality were higher, ranging between 34% and 63% in Whitehall II and between 36% and 50% in UK Biobank.

Interpretation

In two well-characterised cohort studies, up to one third of the social inequalities in incidence of dementia was attributable to cardiovascular health factors. Promotion of cardiovascular health in midlife may contribute to reducing social inequalities in risk of dementia, in addition to cardiovascular diseases and all-cause mortality. This study used adult measures of SEP, further research is warranted using lifecourse measures of SEP.

Funding

NIH (RF1AG062553).

A biological age model based on physical examination data to predict mortality in a Chinese population

Biological age could be reflective of an individual's health status and aging degree. Limited estimations of biological aging based on physical examination data in the Chinese population have been developed to quantify the rate of aging. We developed and validated a novel aging measure (Balanced-AGE) based on readily available physical health examination data. In this study, a repeated sub-sampling approach was applied to address the data imbalance issue, and this approach significantly improved the performance of biological age (Balanced-AGE) in predicting all-cause mortality with a 10-year time-dependent AUC of 0.908 for all-cause mortality. This mortality prediction tool was found to be effective across different subgroups by age, sex, smoking, and alcohol consumption status. Additionally, this study revealed that individuals who were underweight, smokers, or drinkers had a higher extent of age acceleration. The Balanced-AGE may serve as an effective and generally applicable tool for health assessment and management among the elderly population.

Comparison of Outcomes Following Transcatheter Aortic Valve Replacement Requiring Peripheral Vascular Intervention or Alternative Access

Background Peripheral vascular intervention (PVI) is occasionally required to facilitate delivery system insertion or to treat vascular complications during transfemoral transcatheter aortic valve replacement (TF-TAVR). However, the impact of PVI on outcomes is not well understood. Therefore, we aimed to compare outcomes between TF-TAVR with versus without PVI and between TF-TAVR with PVI versus non-TF-TAVR. Methods and Results We retrospectively reviewed 2386 patients who underwent TAVR with a balloon-expandable valve at a single institution from 2016 to 2020. The primary outcomes were death and major adverse cardiac/cerebrovascular event (MACCE), defined as death, myocardial infarction, or stroke. Of 2246 TF-TAVR recipients, 136 (6.1%) required PVI (89% bailout treatment). During follow-up (median 23.0 months), there were no significant differences between TF-TAVR with and without PVI in death (15.4% versus 20.7%; adjusted HR [aHR], 0.96 [95% CI, 0.58-1.58]) or MACCE (16.9% versus 23.0%; aHR, 0.84 [95% CI, 0.52-1.36]). However, compared with non-TF-TAVR (n=140), TF-TAVR with PVI carried significantly lower rates of death (15.4% versus 40.7%; aHR, 0.42 [95% CI, 0.24-0.75]) and MACCE (16.9% versus 45.0%; aHR, 0.40 [95% CI, 0.23-0.68]). Landmark analyses demonstrated lower outcome rates following TF-TAVR with PVI than non-TF-TAVR both within 60 days (death 0.7% versus 5.7%, P=0.019; MACCE 0.7% versus 9.3%; P=0.001) and thereafter (death 15.0% versus 38.9%, P=0.014; MACCE 16.5% versus 41.3%, P=0.013). Conclusions The need for PVI during TF-TAVR is not uncommon, mainly due to the bailout treatment for vascular complications. PVI is not associated with worse outcomes in TF-TAVR recipients. Even when PVI is required, TF-TAVR is associated with better short- and intermediate-term outcomes than non-TF-TAVR.

A comparison of different methods to adjust survival curves for confounders

Treatment specific survival curves are an important tool to illustrate the treatment effect in studies with time-to-event outcomes. In non-randomized studies, unadjusted estimates can lead to biased depictions due to confounding. Multiple methods to adjust survival curves for confounders exist. However, it is currently unclear which method is the most appropriate in which situation. Our goal is to compare forms of inverse probability of treatment weighting, the G-Formula, propensity score matching, empirical likelihood estimation and augmented estimators as well as their pseudo-values based counterparts in different scenarios with a focus on their bias and goodness-of-fit. We provide a short review of all methods and illustrate their usage by contrasting the survival of smokers and non-smokers, using data from the German Epidemiological Trial on Ankle-Brachial-Index. Subsequently, we compare the methods using a Monte-Carlo simulation. We consider scenarios in which correctly or incorrectly specified models for describing the treatment assignment and the time-to-event outcome are used with varying sample sizes. The bias and goodness-of-fit is determined by taking the entire survival curve into account. When used properly, all methods showed no systematic bias in medium to large samples. Cox regression based methods, however, showed systematic bias in small samples. The goodness-of-fit varied greatly between different methods and scenarios. Methods utilizing an outcome model were more efficient than other techniques, while augmented estimators using an additional treatment assignment model were unbiased when either model was correct with a goodness-of-fit comparable to other methods. These "doubly-robust" methods have important advantages in every considered scenario.

Symptom Control and Survival for People Severely ill With COVID: A Multicentre Cohort Study (CovPall-Symptom)

CONTEXT

Evidence of symptom control outcomes in severe COVID is scant.

OBJECTIVES

To determine changes in symptoms among people severely ill or dying with COVID supported by palliative care, and associations with treatments and survival.

METHODS

Multicentre cohort study of people with COVID across England and Wales supported by palliative care services, during the pandemic in 2020 and 2021. We analysed clinical, demographic and survival data, symptom severity at baseline (referral to palliative care, first COVID assessment) and at three follow-up assessments using the Integrated Palliative care Outcome Scale - COVID version.

RESULTS

We included 572 patients from 25 services, mostly hospital support teams; 496 (87%) were newly referred to palliative care with COVID, 75 (13%) were already supported by palliative care when they contracted COVID. At baseline, patients had a mean of 2.4 co-morbidities, mean age 77 years, a mean of five symptoms, and were often bedfast or semiconscious. The most prevalent symptoms were: breathlessness, weakness/lack of energy, drowsiness, anxiety, agitation, confusion/delirium, and pain. Median time in palliative care was 46 hours; 77% of patients died. During palliative care, breathlessness, agitation, anxiety, delirium, cough, fever, pain, sore/dry mouth and nausea improved; drowsiness became worse. Common treatments were low dose morphine and midazolam. Having moderate to severe breathlessness, agitation and multimorbidity were associated with shorter survival.

CONCLUSION

Symptoms of COVID quickly improved during palliative care. Breathlessness, agitation and multimorbidity could be used as triggers for timelier referral, and symptom guidance for wider specialities should build on treatments identified in this study.

Systematic Review of Survival Analysis in Leprosy Studies-Including the Following Outcomes: Relapse, Impairment of Nerve Function, Reactions and Physical Disability

Leprosy is a public health problem in South American, African and Oceanian countries. National programs need to be evaluated, and the survival analysis model can aid in the construction of new indicators. The aim of this study was to assess the period of time until the outcomes of interest for patients with or exposed to leprosy by means of survival analysis surveys. This review researched articles using the databases of PubMed, Science Direct, Scopus, Scielo and BVS published in English and Portuguese. Twenty-eight articles from Brazil, India, Bangladesh, the Philippines and Indonesia were included. The Kaplan-Meier method, which derives the log-rank test, and Cox's proportional hazards regression, which obtains the hazard ratio, were applied. The mean follow-up until the following outcomes were: (I) leprosy (2.3 years) in the population who were exposed to it, (II) relapse (5.9 years), (III) clinical manifestations before, during and after treatment-nerve function impairment (5.2 years), leprosy reactions (4.9 years) and physical disability (8.3 years) in the population of patients with leprosy. Therefore, the use of survival analysis will enable the evaluation of national leprosy programs and assist in the decision-making process to face public health problems.

A Nomogram Model to Predict Post-Progression Survival in Esophageal Squamous Cell Carcinoma Patients With Recurrence After Radical Resection

Background

Esophageal squamous cell carcinoma (ESCC) is characterized clinically by frequent recurrence, leading to a poor prognosis after radical surgery. The aim of this study was to identify a prognostic nomogram to predict the post-progression survival (PPS) of ESCC patients based on the features of primary tumor and recurrence.

Methods

A total of 234 ESCC patients who underwent recurrence after radical surgery were enrolled in this study. The independent prognostic factors screened by the univariate and multivariate Cox regression analysis were subsequently used to construct a nomogram. The predictive performance of the nomogram was evaluated with the concordance index (C-index), decision curve, and the area under the receiver operating characteristic curve (AUC) and validated in two validation cohorts. The Kaplan-Meier curves of different recurrence patterns were analyzed.

Results

The prognostic nomogram of PPS was established by integrating independent prognostic factors, including age, body mass index, number of lymph node dissection, recurrence pattern, and recurrence treatment. The nomogram demonstrated good performance, with C-index values of 0.756, 0.817, and 0.730 for the training and two validation cohorts. The 1-year AUC values were 0.773, 0.798, and 0.735 and 3-year AUC values were 0.832, 0.871, and 0.791, respectively. Furthermore, we found that patients with bone metastasis displayed the worst PPS compared to other isolated recurrence patterns.

Conclusion

We constructed a nomogram to reliably predict PPS, which would be valuable to provide individual managements for ESCC patients after radical surgery.

Rates of serious clinical outcomes in survivors of hospitalisation with COVID-19 in England: a descriptive cohort study within the OpenSAFELY platform

Background: Patients surviving hospitalisation for COVID-19 are thought to be at high risk of cardiometabolic and pulmonary complications, but quantification of that risk is limited. We aimed to describe the overall burden of these complications in people after discharge from hospital with COVID-19.   Methods: Working on behalf of NHS England, we used linked primary care records, death certificate and hospital data from the OpenSAFELY platform. We constructed three cohorts: patients discharged following hospitalisation with COVID-19, patients discharged following pre-pandemic hospitalisation with pneumonia, and a frequency-matched cohort from the general population in 2019. We studied seven outcomes: deep vein thrombosis (DVT), pulmonary embolism (PE), ischaemic stroke, myocardial infarction (MI), heart failure, AKI and new type 2 diabetes mellitus (T2DM) diagnosis. Absolute rates were measured in each cohort and Fine and Gray models were used to estimate age/sex adjusted subdistribution hazard ratios comparing outcome risk between discharged COVID-19 patients and the two comparator cohorts. Results: Amongst the population of 77,347 patients discharged following hospitalisation with COVID-19, rates for the majority of outcomes peaked in the first month post-discharge, then declined over the following four months. Patients in the COVID-19 population had markedly higher risk of all outcomes compared to matched controls from the 2019 general population. Across the whole study period, the risk of outcomes was more similar when comparing patients discharged with COVID-19 to those discharged with pneumonia in 2019, although COVID-19 patients had higher risk of T2DM (15.2 versus 37.2 [rate per 1,000-person-years for COVID-19 versus pneumonia, respectively]; SHR, 1.46 [95% CI: 1.31 - 1.63]).  Conclusions: Risk of cardiometabolic and pulmonary adverse outcomes is markedly raised following discharge from hospitalisation with COVID-19 compared to the general population. However, excess risks were similar to those seen following discharge post-pneumonia. Overall, this suggests a large additional burden on healthcare resources.

Pulmonary Vascular Resistance Predicts Mortality and Graft Failure in Transplantation Patients With Portopulmonary Hypertension

Portopulmonary hypertension (POPH) is a pulmonary vascular disease associated with significant morbidity and mortality in those with liver disease, conferring a higher mortality in patients awaiting liver transplantation (LT). Although not a transplant indication, patients with POPH can experience significant clinical improvement following LT, and those maintaining a mean pulmonary artery pressure (MPAP) <35mm Hg and a pulmonary vascular resistance (PVR) <5 Woods units (WU) are granted additional listing points to expedite LT. The effect of POPH on posttransplant outcomes such as mortality and graft failure, however, is not well defined. We performed a retrospective cohort study of the US Organ Procurement and Transplantation Network database of all adult patients who underwent LT between January 1, 2006, and December 1, 2020. Using adjusted accelerated failure time models, we examined the relationship between a diagnosis of POPH and outcomes following LT and the relationship between pre-LT hemodynamics and post-LT survival (alive with a functioning graft) in patients with POPH. Compared with those undergoing transplants without exception points, patients with POPH had comparable post-LT survival rates but were significantly more likely to have graft failure. Both pre-LT MPAP and PVR predicted post-LT survival in POPH, with a pre-LT PVR of ≥1.6 WU, more than doubling the hazard for mortality (death or a nonfunctioning graft; coefficient, 2.01; standard error, 0.85; hazard ratio, 2.21; P = 0.02). POPH may confer a significantly higher risk of post-LT graft failure compared with patients with cirrhosis without POPH, and a pre-LT PVR of ≥1.6 WU may predict post-LT survival. Further investigation into the relationship between pre-LT hemodynamics, right ventricular function, and post-LT outcomes of mortality and graft failure in POPH is needed.

Corticosteroid treatment and mortality in mechanically ventilated COVID-19-associated acute respiratory distress syndrome (ARDS) patients: a multicentre cohort study

BACKGROUND

Some unanswered questions persist regarding the effectiveness of corticosteroids for severe coronavirus disease 2019 (COVID-19) patients. We aimed to assess the clinical effect of corticosteroids on intensive care unit (ICU) mortality among mechanically ventilated COVID-19-associated acute respiratory distress syndrome (ARDS) patients.

METHODS

This was a retrospective study of prospectively collected data conducted in 70 ICUs (68 Spanish, one Andorran, one Irish), including mechanically ventilated COVID-19-associated ARDS patients admitted between February 6 and September 20, 2020. Individuals who received corticosteroids for refractory shock were excluded. Patients exposed to corticosteroids at admission were matched with patients without corticosteroids through propensity score matching. Primary outcome was all-cause ICU mortality. Secondary outcomes were to compare in-hospital mortality, ventilator-free days at 28 days, respiratory superinfection and length of stay between patients with corticosteroids and those without corticosteroids. We performed survival analysis accounting for competing risks and subgroup sensitivity analysis.

RESULTS

We included 1835 mechanically ventilated COVID-19-associated ARDS, of whom 1117 (60.9%) received corticosteroids. After propensity score matching, ICU mortality did not differ between patients treated with corticosteroids and untreated patients (33.8% vs. 30.9%; p = 0.28). In survival analysis, corticosteroid treatment at ICU admission was associated with short-term survival benefit (HR 0.53; 95% CI 0.39-0.72), although beyond the 17th day of admission, this effect switched and there was an increased ICU mortality (long-term HR 1.68; 95% CI 1.16-2.45). The sensitivity analysis reinforced the results. Subgroups of age < 60 years, severe ARDS and corticosteroids plus tocilizumab could have greatest benefit from corticosteroids as short-term decreased ICU mortality without long-term negative effects were observed. Larger length of stay was observed with corticosteroids among non-survivors both in the ICU and in hospital. There were no significant differences for the remaining secondary outcomes.

CONCLUSIONS

Our results suggest that corticosteroid treatment for mechanically ventilated COVID-19-associated ARDS had a biphasic time-dependent effect on ICU mortality. Specific subgroups showed clear effect on improving survival with corticosteroid use. Therefore, further research is required to identify treatment-responsive subgroups among the mechanically ventilated COVID-19-associated ARDS patients.

Predictors of outcomes following liver transplant in hepatopulmonary syndrome: An OPTN database analysis

Hepatopulmonary syndrome (HPS) is a type of pulmonary vascular disease occurring exclusively in those with underlying liver disease, associated with significant mortality in patients awaiting liver transplantation (LT). LT is curative in HPS, and these patients are granted Model for End Stage Liver Disease (MELD) exception points to expedite LT. The purpose of this study is to use multivariable competing risk Accelerated Failure Time models and propensity matching to examine the relationship between pre-LT hypoxemia and post-LT outcomes in HPS. We performed a retrospective cohort study of UNOS/OPTN database of all adult patients undergoing LT between January 1, 2006 and January 12, 2020. Pre-LT PaO₂ was significantly associated with post-LT mortality in HPS, with each 1 mmHg increase in PaO₂ significantly decreasing the risk of post-LT mortality (coefficient 0.039, HR = 0.95, p = 0.001). HPS patients with a pre-LT PaO₂ < 54 mmHg demonstrated increased mortality following LT as compared to matched non-HPS cirrhotic patients. We conclude that HPS patients with a PaO₂, 54 mmHg are at increased risk of post-LT mortality and may identify high-risk patients who would benefit from additional resources during LT, and that the effects of HPS MELD exception points to optimize post-LT outcomes should be continuously re-evaluated.

Initiation of Breastfeeding in Low- and Middle-Income Countries: A Time-to-Event Analysis

OBJECTIVE

Early breastfeeding has numerous benefits for both the mother and her baby. Previous research typically analyzes breastfeeding initiation in binary terms (within the first hour or day). Although delays are associated with cesarean delivery and skin-to-skin contact may facilitate early breastfeeding, a more nuanced understanding of these relationships is needed.

METHODS

With data from 31 countries that had a Demographic and Health Survey since 2015, we described breastfeeding initiation among babies most recently born in the last 2 years to women aged 15-49 years. In a subset of 21 countries, we conducted survival analysis with multivariable log-logistic accelerated failure time (AFT) regressions to examine factors associated with time to initiation of breastfeeding, specifically the mode of delivery and skin-to-skin contact, controlling for receipt of health care as well as socioeconomic and demographic characteristics of mothers and babies.

FINDINGS

Babies in most countries began breastfeeding within a few hours after birth. The mean time to initiation of breastfeeding ranged from 1.7 hours in Burundi to 32 hours in Pakistan and 40 hours in Chad. In most countries (24 of 31), the median time was 0.5 hours. Median time to initiation was greater for births by cesarean delivery compared with vaginal births at health facilities. After controlling for covariates, AFT models showed significant delays in breastfeeding among cesarean deliveries in most countries, with as much as a 9-fold delay in Senegal. Immediate skin-to-skin contact was significantly associated with a shorter time to initiation.

CONCLUSION

Efforts to promote early breastfeeding should encourage skin-to-skin and target cesarean deliveries.

A systematic review of the quality of conduct and reporting of survival analyses of tuberculosis outcomes in Africa

BACKGROUND

Survival analyses methods (SAMs) are central to analysing time-to-event outcomes. Appropriate application and reporting of such methods are important to ensure correct interpretation of the data. In this study, we systematically review the application and reporting of SAMs in studies of tuberculosis (TB) patients in Africa. It is the first review to assess the application and reporting of SAMs in this context.

METHODS

Systematic review of studies involving TB patients from Africa published between January 2010 and April 2020 in English language. Studies were eligible if they reported use of SAMs. Application and reporting of SAMs were evaluated based on seven author-defined criteria.

RESULTS

Seventy-six studies were included with patient numbers ranging from 56 to 182,890. Forty-three (57%) studies involved a statistician/epidemiologist. The number of published papers per year applying SAMs increased from two in 2010 to 18 in 2019 (P = 0.004). Sample size estimation was not reported by 67 (88%) studies. A total of 22 (29%) studies did not report summary follow-up time. The survival function was commonly presented using Kaplan-Meier survival curves (n = 51, (67%) studies) and group comparisons were performed using log-rank tests (n = 44, (58%) studies). Sixty seven (91%), 3 (4.1%) and 4 (5.4%) studies reported Cox proportional hazard, competing risk and parametric survival regression models, respectively. A total of 37 (49%) studies had hierarchical clustering, of which 28 (76%) did not adjust for the clustering in the analysis. Reporting was adequate among 4.0, 1.3 and 6.6% studies for sample size estimation, plotting of survival curves and test of survival regression underlying assumptions, respectively. Forty-five (59%), 52 (68%) and 73 (96%) studies adequately reported comparison of survival curves, follow-up time and measures of effect, respectively.

CONCLUSION

The quality of reporting survival analyses remains inadequate despite its increasing application. Because similar reporting deficiencies may be common in other diseases in low- and middle-income countries, reporting guidelines, additional training, and more capacity building are needed along with more vigilance by reviewers and journal editors.

Description of symptom course in a telemedicine monitoring clinic for acute symptomatic COVID-19: a retrospective cohort study

OBJECTIVE

Describe the disease course in a cohort of outpatients with COVID-19 and evaluate factors predicting duration of symptoms.

DESIGN

Retrospective cohort study.

SETTING

Telemedicine clinic at a large medical system in Atlanta, Georgia.

PARTICIPANTS

337 patients with acute COVID-19. Exclusion criteria included intake visit more than 10 days after symptom onset and hospitalisation prior to intake visit.

MAIN OUTCOME MEASURES

Symptom duration in days.

RESULTS

Common symptoms at intake visit are upper respiratory (73% cough, 55% loss of smell or taste, 57% sinus congestion, 32% sore throat) and systemic (66% headache, 64% body aches, 53% chills, 30% dizziness, 36% fever). Day of symptom onset was earliest for systemic and upper respiratory symptoms (median onset day 1 for both), followed by lower respiratory symptoms (day 3, 95% CI 2 to 4), with later onset of gastrointestinal symptoms (day 4, 95% CI 3 to 5), when present. Cough had the longest duration when present with median 17 days (95% CI 15 to 21), with 42% not resolved at final visit. Loss of smell or taste had the second longest duration with 14 days (95% CI 12 to 17), with 38% not resolved at final visit. Initial symptom severity is a significant predictor of symptom duration (p<0.01 for multiple symptoms).

CONCLUSIONS

COVID-19 illness in outpatients follows a pattern of progression from systemic symptoms to lower respiratory symptoms and persistent symptoms are common across categories. Initial symptom severity is a significant predictor of disease duration for most considered symptoms.