Statins and lower mortality in rheumatic diseases: An effect of immortal time bias?

Breaking Down Bias: A Methodological Primer on Identifying, Evaluating, and Mitigating Bias in Cardiovascular Research

Systematic error, often referred to as bias is an inherent challenge in observational cardiovascular research, and has the potential to profoundly influence the design, conduct, and interpretation of study results. If not carefully considered and managed, bias can lead to spurious results, which can misinform clinical practice or public health initiatives and compromise patient outcomes. This methodological primer offers a concise introduction to identifying, evaluating, and mitigating bias in observational cardiovascular research studies that examine the causal association between an exposure (or treatment) and an outcome. Using high-profile examples from the cardiovascular literature, this review provides a theoretical overview of 3 main types of bias-selection bias, information bias, and confounding-and discusses the implications of specialized types of biases commonly encountered in longitudinal cardiovascular research studies, namely, competing risks, immortal time bias, and confounding by indication. Furthermore, strategies and tools that can be used to minimize and assess the influence of bias are highlighted, with a specific focus on using the target trial framework, directed acyclic graphs, quantitative bias analysis, and formal risk of bias assessments. This review aims to assist researchers and health care professionals in designing observational studies and selecting appropriate methodologies to reduce bias, ultimately enhancing the estimation of causal associations in cardiovascular research.

Real-World Effectiveness of All-Oral Direct-Acting Antivirals in Patients With Hepatitis C Virus-Related HCC

The association between direct-acting antiviral (DAA) treatment and hepatitis C virus (HCV)-related hepatocellular carcinoma (HCC) is currently unclear. Hence, we aim to assess the association between DAA treatment and mortality rate among Medicare beneficiaries with HCV-related HCC. This retrospective cohort study screened 19,813 adults in 2013-2019 Surveillance, Epidemiology, and End Results data linked with Medicare data. Patients with HCV-related HCC initiating DAA therapy after their first HCC diagnosis were compared with patients with HCV-related HCC who received no HCV treatment. After inverse probability treatment weighting, multivariable Cox proportional hazards models compared mortality rates between the groups. Subgroup and sensitivity analyses were based on HCC stage (early vs. advanced), type of HCC treatment (curative, palliative, none), and DAA treatment duration. In total 3,777 patients with HCV-related HCC were identified (mean age: 68.2 years, 75.2% male, 61.8% White), of whom 19% initiated DAA therapy. Crude incidence mortality rates were 17.9 and 90.7 deaths per 100 person-years in the DAA and HCV-untreated groups, respectively. Cox regression models indicated that DAA therapy was associated with decreased risk of all-cause mortality (adjusted hazard ratio, 0.33; 95% CI 0.31-0.36). Median survival time was 45.7 (95% CI 40.9-57.9) months in the DAA group and 7.7 (95% CI 7.3-8.2) months in the HCV-untreated group (P < 0.001). All subgroup and sensitivity analyses were consistent with the main analyses. DAA therapy was associated with survival benefits for patients with HCV-related HCC regardless of the stage or type of HCC treatment and should not be withheld from this population of Medicare beneficiaries.

Mortality in patients with incident rheumatoid arthritis and depression: a Danish cohort study of 11 071 patients and 55 355 comparators

OBJECTIVES

In patients with RA, the association between mortality and depression has been investigated only in patients with prevalent RA. In this study, we estimated the mortality risk associated with depression, defined as the first filling of a prescription for antidepressants, in patients with incident RA and background population comparators.

METHODS

From 2008 to 2018, we identified patients with incident RA in the nationwide Danish rheumatologic database, DANBIO. For each patient, we randomly selected five comparators. Participants were not treated with antidepressants or diagnosed with depression 3 years prior to the index date. From other registers we collected data on socioeconomic status, mortality and cause of death using unique personal identifiers. Using Cox models, we calculated hazard rate ratios (HRR) with 95% CI.

RESULTS

In depressed patients with RA vs patients without depression, adjusted HRR for all-cause mortality was 5.34 (95% CI 3.02, 9.45) during 0-2 years and 3.15 (95% CI 2.62, 3.79) during the total follow-up period, and highest in patients <55 years with HRR 8.13 (95% CI 3.89, 17.02). In comparators with depression vs comparators without depression, the association with mortality was similar to that in patients with RA. There were no unnatural causes of death among depressed patients with RA. The most frequent natural causes of death were cancer, cardiovascular disease, stroke and pneumonia.

CONCLUSION

In patients with RA, depression was a predictor of death but with a strength similar to that in matched comparators.

Reduction of Cardiovascular Disease and Mortality Versus Risk of New-Onset Diabetes Mellitus With Statin Use in Patients With Rheumatoid Arthritis

OBJECTIVE

To assess the effect of statin use on the risk of cardiovascular disease (CVD), all-cause mortality, and type 2 diabetes mellitus (DM) in patients with rheumatoid arthritis (RA).

METHODS

We identified a cohort of patients with RA between 1989 and 2018, within the UK Clinical Practice Research Datalink. We employed a prevalent new-user cohort design by which patients initiating statins were each matched to 2 concurrent nonusers by the time-conditional propensity score (TCPS). Patients were followed until the occurrence of the composite end point of myocardial infarction, stroke, hospitalized heart failure or CVD mortality, all-cause mortality, and incident type 2 DM. The Cox proportional hazards model was used to estimate the hazard ratio (HR) of each outcome associated with as-treated statin use, with adjustment for TCPS deciles and imbalanced covariables.

RESULTS

Among 1,768 statin initiators and 3,528 nonusers, 63 versus 340 CVD (3.0 per 100 person-years versus 2.7 per 100 person-years) and 62 versus 525 deaths (2.8 per 100 person-years versus 4.1 per 100 person-years) occurred. Incident type 2 DM was noted in 128 of 3,608 statin initiators (3.0 per 100 person-years) and 518 of 7,208 nonusers (2.0 per 100 person-years). Statin initiation was associated with 32% (HR 0.68 [95% confidence interval (95% CI) 0.51-0.90]) reduction in CVD, 54% (HR 0.46 [95% CI 0.35-0.60]) reduction in all-cause mortality, and 33% increase in type 2 DM (HR 1.33 [95% CI 1.09-1.63]). The number needed to treat/number needed to harm to prevent a CVD or all-cause mortality or to cause type 2 DM in 1 year was 102, 42, and 127, respectively.

CONCLUSION

Statins are associated with important reductions in CVD and mortality that outweigh the modest increase in type 2 DM risk in RA patients.

The influence of immortal time bias in observational studies examining associations of antifibrotic therapy with survival in idiopathic pulmonary fibrosis: A simulation study

Background

Immortal time bias (ITB) has been overlooked in idiopathic pulmonary fibrosis (IPF). We aimed to identify the presence of ITB in observational studies examining associations between antifibrotic therapy and survival in patients with IPF and illustrate how ITB may affect effect size estimates of those associations.

Methods

Immortal time bias was identified in observational studies using the ITB Study Assessment Checklist. We used a simulation study to illustrate how ITB may affect effect size estimates of antifibrotic therapy on survival in patients with IPF based on four statistical techniques including time-fixed, exclusion, time-dependent and landmark methods.

Results

Of the 16 included IPF studies, ITB was detected in 14 studies, while there were insufficient data for assessment in two others. Our simulation study showed that use of time-fixed [hazard ratio (HR) 0.55, 95% confidence interval (CI) 0.47-0.64] and exclusion methods (HR 0.79, 95% CI 0.67-0.92) overestimated the effectiveness of antifibrotic therapy on survival in simulated subjects with IPF, in comparison of the time-dependent method (HR 0.93, 95% CI 0.79-1.09). The influence of ITB was mitigated using the 1 year landmark method (HR 0.69, 95% CI 0.58-0.81), compared to the time-fixed method.

Conclusion

The effectiveness of antifibrotic therapy on survival in IPF can be overestimated in observational studies, if ITB is mishandled. This study adds to the evidence for addressing the influence of ITB in IPF and provides several recommendations to minimize ITB. Identifying the presence of ITB should be routinely considered in future IPF studies, with the time-dependent method being an optimal approach to minimize ITB.

The Intersection of Cellular and Systemic Metabolism: Metabolic Syndrome in Systemic Lupus Erythematosus

A high prevalence of metabolic syndrome (MetS) has been reported in multiple cohorts of systemic lupus erythematosus (SLE) patients, most likely as one of the consequences of autoimmune pathogenesis. Although MetS has been associated with inflammation, its consequences on the lupus immune system and on disease manifestations are largely unknown. The metabolism of immune cells is altered and overactivated in mouse models as well as in patients with SLE, and several metabolic inhibitors have shown therapeutic benefits. Here we review recent studies reporting these findings, as well as the effect of dietary interventions in clinical and preclinical studies of SLE. We also explore potential causal links between systemic and immunometabolism in the context of lupus, and the knowledge gap that needs to be addressed.

Cardiovascular Risk Prediction Parameters for Better Management in Rheumatic Diseases

The early detection of cardiovascular disease (CVD) serves as a key element in preventive cardiology. The risk of developing CVD in patients with rheumatic disease is higher than that of the general population. Thus, the objective of this narrative review was to assess and describe updated risk-prediction parameters for CVD in patients suffering from rheumatic diseases, and, additionally, to evaluate therapeutic and risk management possibilities. The processes of recognizing CVD risk factors in rheumatic diseases, establishing diagnoses, and discovering CV risk assessments are currently displeasing in clinical practice; they have a limited clinical impact. A large number of references were found while screening PUBMED, Scopus, and Google scholar databases; the 47 most relevant references were utilized to build up this study. The selection was limited to English language full text articles, RCTs, and reviews published between 2011 and 2021. Multiple imaging techniques, such as ECG, ultrasound, and cIMT, as well as biomarkers like osteoprotegerin cytokine receptor and angiopoietin-2, can be beneficial in both CV risk prediction and in early subclinical diagnosis. Physical exercise is an essential non-pharmacological intervention that can maintain the health of the cardiovascular system and, additionally, influence the underlying disease. Lipid-lowering drugs (methotrexate from the non-biologic DMARDs family as well as biologic DMARDs such as anti-TNF) were all associated with a lower CV risk; however, anti-TNF medication can decrease cardiac compliance and promote heart failure in patients with previously diagnosed chronic HF. Although they achieved success rates in reducing inflammation, glucocorticoids, NSAIDs, and COX-2 inhibitors were correlated with an increased risk of CVD. When taking all of the aforementioned points into consideration, there appears to be a dire need to establish and implement CVD risk stratification models in rheumatic patients.

Carotid Artery Pathology in Inflammatory Diseases

There is considerable evidence that patients with inflammatory conditions are at higher risk of developing cardiovascular (CV) disease including carotid artery stenosis. CV disease accounts for 35-50% of the excess mortality in patients with inflammatory diseases such as rheumatoid arthritis, with cerebrovascular disease being the second leading cause of death. We review current evidence regarding the association of inflammatory conditions and specifically carotid artery disease. Clinical epidemiological observations suggest that mechanisms other than classic risk factors may promote accelerated atherogenesis in rheumatoid and other inflammatory arthritis and carotid artery disease is increased in individuals with these conditions. Additional studies to better understand the underlying mechanisms and targeted strategies to mitigate such risk are indicated. For now, lifestyle modifications, aggressive treatment of risk factors and lipid lowering therapy in appropriate individuals is indicated.

Cholesterol metabolism related genes in osteoarthritis

Cholesterol homeostasis plays a significant role in skeletal development and the dysregulation of cholesterol-related mechanism has been shown to be involved in the development of cartilage diseases including osteoarthritis (OA). Epidemiological studies have shown an association between elevated serum cholesterol levels and OA. Furthermore, abnormal lipid accumulation in chondrocytes as a result of abnormal regulation of cholesterol homeostasis has been demonstrated to be involved in the development of OA. Although, many in vivo and in vitro studies support the connection between cholesterol and cartilage degradation, the mechanisms underlying the complex interactions between lipid metabolism, especially HDL cholesterol metabolism, and OA remain unclear. The current review aims to address this problem and focuses on key molecular players of the HDL metabolism pathway and their role in ΟΑ pathogenesis. Understanding the complexity of biological processes implicated in OA pathogenesis, such as cholesterol metabolism, may lead to new targets for drug therapy of OA patients.

Time to administration of antibiotics and mortality in sepsis

OBJECTIVE

To examine the association between delay of antibiotic treatment and 28-day mortality in a study of septic patients identified by the Sepsis-3 criteria.

METHODS

A prospective observational cohort study of patients (≥ 18 years) with sepsis admitted to a Danish emergency department between October 2017 and March 2018. The interval between arrival to the ED and first delivery of antibiotics was used as time to antibiotic treatment (TTA). Logistic regression was used in the analysis of the association between TTA and mortality adjusted for potential confounding.

RESULTS

A total of 590 patients, median age 74.2 years, were included. Overall 28-day mortality was 14.6% (95% confidence interval [CI], 11.8-17.7). Median TTA was 4.7 hours (interquartile range 2.7-8.1). The mortality in patients with TTA ≤1 hour was 26.5% (95% CI, 12.8-44.4), and 15.3% (95% CI, 9.8-22.5), 10.5% (95% CI, 6.6-15.8), and 12.8 (95% CI, 7.3-20.1) in the timespans 1-3, 3-6, and 6-9 hours, respectively, and 18.8% (95% CI, 12.0-27.2) in patients with TTA >9 hours. With patients with lowest mortality (TTA timespan 3-6 hours) as reference, the adjusted odds ratio of mortality was 4.53 (95% CI, 1.67-3.37) in patients with TTA ≤1 hour, 1.67 (95% CI, 0.83-3.37) in TTA timespan 1-3 hours, 1.17 (95% CI, 0.56-2.49) in timespan 6-9 hours, and 1.91 (95% CI, 0.96-3.85) in patient with TTA >9 hours.

CONCLUSIONS

The adjusted odds of 28-day mortality were lowest in emergency department (ED) patients with sepsis who received antibiotics between 1 and 9 hours and highest in patients treated within 1 and >9 hours after admission to the ED.

Effectiveness of Allopurinol in Reducing Mortality: Time-Related Biases in Observational Studies

OBJECTIVE

The treatment of gout with allopurinol is effective at reducing urate levels and the frequency of flares. Several observational studies have shown important reductions in mortality with allopurinol use, with wide variations in results. We undertook this review to assess the extent of bias in these studies, particularly time-related biases such as immortal time bias.

METHODS

We searched the literature to identify all observational studies describing the effect of allopurinol use versus nonuse on all-cause mortality.

RESULTS

We identified 12 observational studies, of which 3 were affected by immortal time bias and 3 by immeasurable time bias, while the remaining 6 studies avoided these time-related biases. Reductions in all-cause mortality with allopurinol use were observed among the studies with immortal time bias, with a pooled hazard ratio (HR) of death associated with allopurinol of 0.71 (95% confidence interval [95% CI] 0.50-1.01), as well as in those with immeasurable time bias (pooled HR 0.62 [95% CI 0.56-0.67]). The 6 studies that avoided these biases demonstrated a null effect of allopurinol on mortality (pooled HR 0.99 [95% CI 0.87-1.11]), though the lack of an analysis based on treatment adherence may have attenuated the effect.

CONCLUSION

Observational studies are important to provide real-world data on medication effects. The observational studies showing significantly decreased mortality with allopurinol treatment cannot be used as evidence, however, mainly due to time-related biases that tend to greatly exaggerate the potential benefit of treatments. The ALL-HEART randomized trial, which is currently underway and evaluates the effect of adding allopurinol to usual care (compared to no added treatment), will provide reliable evidence on mortality.