Estimating the causal effects of cumulative treatment episodes for adolescents using marginal structural models and inverse probability of treatment weighting

Outcomes of carotid revascularization stratified by procedure in patients with an estimated glomerular filtration rate of <30 and dialysis patients

OBJECTIVE

Renal failure is a predictor of adverse outcomes in carotid revascularization. There has been debate regarding the benefit of revascularization in patients with severe chronic kidney disease or on dialysis.

METHODS

Patients in the Vascular Quality Initiative undergoing transcarotid artery revascularization (TCAR), transfemoral carotid artery stenting (tfCAS), or CEA between 2016 and 2023 with an estimated glomerular filtration rate (eGFR) of <30 mL/min/1.73 m2 or on dialysis were included. Patients were divided into cohorts based on procedure. Additional analyses were performed for patients on dialysis only and by symptomatology. Primary outcomes were perioperative stroke/death/myocardial infarction (MI) (SDM). Secondary outcomes included perioperative death, stroke, MI, cranial nerve injury, and stroke/death. Inverse probability of treatment weighting was performed based on treatment assignment to TCAR, tfCAS, and CEA patients and adjusted for demographics, comorbidities, and preoperative symptoms. The χ2 test and multivariable logistic regression analysis were used to evaluate the association of procedure with perioperative outcomes in the weighted cohort. Five-year survival was evaluated using Kaplan-Meier and weighted Cox regression.

RESULTS

In the weighted cohort, 13,851 patients with an eGFR of <30 (2506 on dialysis) underwent TCAR (3639; 704 on dialysis), tfCAS (1975; 393 on dialysis), or CEA (8237; 1409 on dialysis) during the study period. Compared with TCAR, CEA had higher odds of SDM (2.8% vs 3.6%; adjusted odds ratio [aOR], 1.27; 95% confidence interval [CI], 1.00-1.61; P = .049), and MI (0.7% vs 1.5%; aOR, 2.00; 95% CI, 1.31-3.05; P = .001). Compared with TCAR, rates of SDM (2.8% vs 5.8%), stroke (1.2% vs 2.6%), and death (0.9% vs 2.4%) were all higher for tfCAS. In asymptomatic patients CEA patients had higher odds of MI (0.7% vs 1.3%; aOR, 1.85; 95% CI, 1.15-2.97; P = .011) and cranial nerve injury (0.3% vs 1.9%; aOR, 7.23; 95% CI, 3.28-15.9; P < .001). Like in the primary analysis, asymptomatic tfCAS patients demonstrated higher odds of death and stroke/death. Symptomatic CEA patients demonstrated no difference in stroke, death, or stroke/death. Although tfCAS patients demonstrated higher odds of death, stroke, MI, stroke/death, and SDM. In both groups, the 5-year survival was similar for TCAR and CEA (eGFR <30, 75.1% vs 74.2%; aHR, 1.06; P = .3) and lower for tfCAS (eGFR <30, 75.1% vs 70.4%; aHR, 1.44; P < .001).

CONCLUSIONS

CEA and TCAR had similar odds of stroke and death and are both a reasonable choice in this population; however, TCAR may be better in patients with an increased risk of MI. Additionally, tfCAS patients were more likely to have worse outcomes after weighting for symptom status. Finally, although patients with a reduced eGFR have worse outcomes than their healthy peers, this analysis shows that the majority of patients survive long enough to benefit from the potential stroke risk reduction provided by all revascularization procedures.

Seven years of the transcarotid artery revascularization surveillance project, comparison to transfemoral stenting and endarterectomy

OBJECTIVE

This study utilizes the latest data from the Vascular Quality Initiative (VQI), which now encompasses over 50,000 transcarotid artery revascularization (TCAR) procedures, to offer a sizeable dataset for comparing the effectiveness and safety of TCAR, transfemoral carotid artery stenting (tfCAS), and carotid endarterectomy (CEA). Given this substantial dataset, we are now able to compare outcomes overall and stratified by symptom status across revascularization techniques.

METHODS

Utilizing VQI data from September 2016 to August 2023, we conducted a risk-adjusted analysis by applying inverse probability of treatment weighting to compare in-hospital outcomes between TCAR vs tfCAS, CEA vs tfCAS, and TCAR vs CEA. Our primary outcome measure was in-hospital stroke/death. Secondary outcomes included myocardial infarction and cranial nerve injury.

RESULTS

A total of 50,068 patients underwent TCAR, 25,361 patients underwent tfCAS, and 122,737 patients underwent CEA. TCAR patients were older, more likely to have coronary artery disease, chronic kidney disease, and undergo coronary artery bypass grafting/percutaneous coronary intervention as well as prior contralateral CEA/CAS compared with both CEA and tfCAS. TfCAS had higher odds of stroke/death when compared with TCAR (2.9% vs 1.6%; adjusted odds ratio [aOR], 1.84; 95% confidence interval [CI], 1.65-2.06; P < .001) and CEA (2.9% vs 1.3%; aOR, 2.21; 95% CI, 2.01-2.43; P < .001). CEA had slightly lower odds of stroke/death compared with TCAR (1.3% vs 1.6%; aOR, 0.83; 95% CI, 0.76-0.91; P < .001). TfCAS had lower odds of cranial nerve injury compared with TCAR (0.0% vs 0.3%; aOR, 0.00; 95% CI, 0.00-0.00; P < .001) and CEA (0.0% vs 2.3%; aOR, 0.00; 95% CI, 0.0-0.0; P < .001) as well as lower odds of myocardial infarction compared with CEA (0.4% vs 0.6%; aOR, 0.67; 95% CI, 0.54-0.84; P < .001). CEA compared with TCAR had higher odds of myocardial infarction (0.6% vs 0.5%; aOR, 1.31; 95% CI, 1.13-1.54; P < .001) and cranial nerve injury (2.3% vs 0.3%; aOR, 9.42; 95% CI, 7.78-11.4; P < .001).

CONCLUSIONS

Although tfCAS may be beneficial for select patients, the lower stroke/death rates associated with CEA and TCAR are preferred. When deciding between CEA and TCAR, it is important to weigh additional procedural factors and outcomes such as myocardial infarction and cranial nerve injury, particularly when stroke/death rates are similar. Additionally, evaluating subgroups that may benefit from one procedure over another is essential for informed decision-making and enhanced patient care in the treatment of carotid stenosis.

Assessing Covariate Balance with Small Sample Sizes

Propensity score adjustment addresses confounding by balancing covariates in subject treatment groups through matching, stratification, inverse probability weighting, etc. Diagnostics ensure that the adjustment has been effective. A common technique is to check whether the standardized mean difference for each relevant covariate is less than a threshold like 0.1. For small sample sizes, the probability of falsely rejecting the validity of a study because of chance imbalance when no underlying balance exists approaches 1. We propose an alternative diagnostic that checks whether the standardized mean difference statistically significantly exceeds the threshold. Through simulation and real-world data, we find that this diagnostic achieves a better trade-off of type 1 error rate and power than standard nominal threshold tests and not testing for sample sizes from 250 to 4000 and for 20 to 100,000 covariates. In network studies, meta-analysis of effect estimates must be accompanied by meta-analysis of the diagnostics or else systematic confounding may overwhelm the estimated effect. Our procedure for statistically testing balance at both the database level and the meta-analysis level achieves the best balance of type-1 error rate and power. Our procedure supports the review of large numbers of covariates, enabling more rigorous diagnostics.

A tutorial comparing different covariate balancing methods with an application evaluating the causal effects of substance use treatment programs for adolescents

Randomized controlled trials are the gold standard for measuring causal effects. However, they are often not always feasible, and causal treatment effects must be estimated from observational data. Observational studies do not allow robust conclusions about causal relationships unless statistical techniques account for the imbalance of pretreatment confounders across groups and key assumptions hold. Propensity score and balance weighting (PSBW) are useful techniques that aim to reduce the observed imbalances between treatment groups by weighting the groups to look alike on the observed confounders. Notably, there are many methods available to estimate PSBW. However, it is unclear a priori which will achieve the best trade-off between covariate balance and effective sample size for a given application. Moreover, it is critical to assess the validity of key assumptions required for robust estimation of the needed treatment effects, including the overlap and no unmeasured confounding assumptions. We present a step-by-step guide to the use of PSBW for estimation of causal treatment effects that includes steps on how to evaluate overlap before the analysis, obtain estimates of PSBW using multiple methods and select the optimal one, check for covariate balance on multiple metrics, and assess sensitivity of findings (both the estimated treatment effect and statistical significance) to unobserved confounding. We illustrate the key steps using a case study examining the relative effectiveness of substance use treatment programs and provide a user-friendly Shiny application that can implement the proposed steps for any application with binary treatments.

Comparative effectiveness of individual versus family-based substance use treatment on adolescent self-injurious thoughts and behaviors

INTRODUCTION

Self-injurious thoughts and behaviors (SITB) are of increasing concern among adolescents, especially those who use substances. Some evidence suggests that existing evidence-based substance use treatments (EBTs) could impact not only their intended substance use targets but also SITB. However, which types of substance use treatments may have the greatest impact on youth SITB is not yet clear. Based on prior literature showing that family support and connection may buffer youth from SITB, we initially hypothesized that family-based EBTs would show greater improvement in SITB compared to those receiving individually focused EBTs and that the size of the effects would be small given the comparison between two active, evidence-based interventions, and base rates of SITB.

METHODS

In a sample of 2893 youth in substance use treatment, we compared the effectiveness of individually and family-based EBTs in reducing SITBs. The study used entropy balancing and regression modeling to balance the groups on pre-treatment characteristics and examine change in outcomes over a one-year follow-up period.

RESULTS

Both groups improved in self-injury and suicide attempts over the one-year study period, but only youth in individual treatment improved in suicidal ideation. However, the study found no significant difference between the changes over time in the two groups for any outcome. As expected, effect sizes were small and power was constrained in this study given the rarity of the outcomes, but effect sizes are similar to those observed with substance use outcomes.

CONCLUSIONS

The results provide important exploratory evidence on the potential relative effectiveness of these two treatments for SITBs. This study supports prior findings that EBTs for youth substance use may help to improve SITB and suggests that different treatment formats (individual or family-based) could result in different benefits for SITB outcomes.

Association Between Enrollment in Maryland's Behavioral Health Homes and Use of Outpatient Mental Health Services

OBJECTIVE

This study examined the association between enrollment in Maryland's behavioral health home (BHH) program and use of outpatient mental health services among people with serious mental illness.

METHODS

The study sample, drawn from Maryland Medicaid administrative claims data from 2012 through 2017, included 12,232 individuals ages 21-64 with a serious mental illness who were enrolled in a BHH (N=3,319) or never enrolled (N=8,913). A marginal structural modeling approach with inverse probability of treatment weighting was used to examine the association between BHH enrollment and outpatient mental health utilization, measured as the number of visits per 3-month period.

RESULTS

BHH enrollment was associated with 0.8 additional outpatient mental health visits per 3-month period, or approximately three additional visits annually.

CONCLUSIONS

A specialty mental health system-based health home model with a primary goal of improving access to general medical care was associated with increased use of outpatient mental health services.

Nonparametric Estimation of Population Average Dose-Response Curves using Entropy Balancing Weights for Continuous Exposures

Weighted estimators are commonly used for estimating exposure effects in observational settings to establish causal relations. These estimators have a long history of development when the exposure of interest is binary and where the weights are typically functions of an estimated propensity score. Recent developments in optimization-based estimators for constructing weights in binary exposure settings, such as those based on entropy balancing, have shown more promise in estimating treatment effects than those methods that focus on the direct estimation of the propensity score using likelihood-based methods. This paper explores recent developments of entropy balancing methods to continuous exposure settings and the estimation of population dose-response curves using nonparametric estimation combined with entropy balancing weights, focusing on factors that would be important to applied researchers in medical or health services research. The methods developed here are applied to data from a study assessing the effect of non-randomized components of an evidence-based substance use treatment program on emotional and substance use clinical outcomes.

Effects of Maryland's Affordable Care Act Medicaid Health Home Waiver on Quality of Cardiovascular Care Among People with Serious Mental Illness

BACKGROUND

Nineteen US states and D.C. have used the Affordable Care Act Medicaid health home waiver to create behavioral health home (BHH) programs for Medicaid beneficiaries with serious mental illness (SMI). BHH programs integrate physical healthcare management and coordination into specialty mental health programs. No studies have evaluated the effects of a BHH program created through the Affordable Care Act waiver on cardiovascular care quality among people with SMI.

OBJECTIVE

To study the effects of Maryland's Medicaid health home waiver BHH program, implemented October 1, 2013, on quality of cardiovascular care among individuals with SMI.

DESIGN

Retrospective cohort analysis using Maryland Medicaid administrative claims data from July 1, 2010, to September 30, 2016. We used marginal structural modeling with inverse probability of treatment weighting to account for censoring and potential time-dependent confounding.

PARTICIPANTS

Maryland Medicaid beneficiaries with diabetes or cardiovascular disease (CVD) participating in psychiatric rehabilitation programs, the setting in which BHHs were implemented. To qualify for psychiatric rehabilitation programs, individuals must have SMI. The analytic sample included BHH and non-BHH participants, N = 2605 with diabetes and N = 1899 with CVD.

MAIN MEASURES

Healthcare Effectiveness Data and Information Set (HEDIS) measures of cardiovascular care quality including annual receipt of diabetic eye and foot exams; HbA1c, diabetic nephropathy, and cholesterol testing; and statin therapy receipt and adherence among individuals with diabetes, as well as HEDIS measures of annual receipt of cholesterol testing and statin therapy and adherence among individuals with CVD.

KEY RESULTS

Relative to non-enrollment, enrollment in Maryland's BHH program was associated with increased likelihood of eye exam receipt among individuals with SMI and co-morbid diabetes, but no changes in other care quality measures.

CONCLUSIONS

Additional financing, infrastructure, and implementation supports may be needed to realize the full potential of Maryland's BHH to improve cardiovascular care for people with SMI.

Expanding outcomes when considering the relative effectiveness of two evidence-based outpatient treatment programs for adolescents

The current study seeks to advance understanding about how to address substance use and co-occurring mental health problems in adolescents. Specifically, we compared the effectiveness of two evidence-based treatment programs (Motivational Enhancement Treatment/Cognitive Behavior Therapy, 5 Sessions [MET/CBT5] and Adolescent Community Reinforcement Approach [A-CRA]) for both substance use and mental health outcomes (i.e., crossover effects). We used statistical methods designed to approximate randomized controlled trials when comparing nonequivalent groups using observational study data. Our methods also included an assessment of the potential impact of omitted variables. We found that after applying balancing weighting to ensure similarity of the baseline samples (given the nonrandomized study design), both groups significantly improved on the two substance use outcomes (days abstinent and percent of youth in recovery) and on the two mental health outcomes (post-traumatic stress disorder (PTSD) symptoms and general emotional problems). Youth in A-CRA were significantly more likely to be in recovery at the 3-month follow-up compared to youth in MET/CBT5, but the size of this effect was very small. Youth receiving MET/CBT5 appeared to show significantly more improvement in the two mental health measures compared to youth in A-CRA, though these effect sizes were also very small. The findings indicate that adolescents with co-occurring substance use and mental health problems improve on both substance use and mental health outcomes with both treatments even though they are not specifically targeting mental health problems.

Causal models adjusting for time-varying confounding-a systematic review of the literature

BACKGROUND

Obtaining unbiased causal estimates from longitudinal observational data can be difficult due to exposure-affected time-varying confounding. The past decade has seen considerable development in methods for analysing such complex longitudinal data. However, the extent to which those methods have been implemented is unclear. This study describes and characterizes the state of the field in methods adjusting for exposure-affected time-varying confounding, and examines their use in the literature.

METHODS

We systematically reviewed the literature from 2000 to 2016 for studies adjusting for time-dependent confounding, including use of specific methods like inverse probability of treatment weighting (IPTW). Articles were coded based on the methods used and, for applied articles, the topic areas covered.

RESULTS

We screened 4239 abstracts, and subsequently reviewed 1100 articles, leaving 542 relevant articles in the analyses. The number of published articles increased from two in 2000, to 112 in 2016. This increase was primarily in applied articles using IPTW, which increased from one study in 2000, to 90 in 2016. Of the 432 studies with applications to observed data, 60.9% were on at least one of: HIV (30.6%), cardiopulmonary health (13.2%), kidney disease (11.8%) or mental health (10.0%).

CONCLUSIONS

There has been marked growth in reports addressing exposure-affected time-varying confounding. This was driven by work in a small number of topic areas, with other areas showing relatively little uptake. In addition, despite developments in more advanced methods such doubly robust techniques and estimation via machine learning, implementation has been largely concentrated on the simpler, yet potentially less robust, IPTW.

The effects of the Maryland Medicaid Health Home Waiver on Emergency Department and inpatient utilization among individuals with serious mental illness

OBJECTIVE

The Maryland Medicaid health home program, established through the Affordable Care Act's Medicaid health home waiver, integrates primary care services into specialty mental health programs for adults with serious mental illness (SMI). We evaluated the effect of this program on all-cause, physical, and behavioral health emergency department (ED) and inpatient utilization.

METHOD

Using marginal structural modeling to control for time-invariant and time-varying confounding, we analyzed Medicaid administrative claims data for 12,232 enrollees with SMI from October 1, 2012 to December 31, 2016; 3319 individuals were enrolled in a BHH and 8913 were never enrolled.

RESULTS

Health home enrollment was associated with reduced probability of all-cause (PP: 0.23 BHH enrollment vs. 0.26 non-enrollment, p < 0.01) and physical health ED visits (PP: 0.21 BHH enrollment vs. 0.24 non-enrollment, p < 0.01) and no effect on inpatient admissions per person-three-month period.

CONCLUSION

These results suggest the Maryland Medicaid health home waiver's focus on supporting physical health care coordination by specialty mental health programs may be preventing ED visits among adults with SMI, although effect sizes are small.

Modelling Long-Term Joint Trajectories of Heroin Use and Treatment Utilisation: Findings from the Australian Treatment Outcome Study

BACKGROUND

Heroin is currently contributing to the worst drug addiction epidemic in United States history; recent rates of use, dependence and death have also increased dramatically in parts of Europe. An improved understanding of the long-term relationship between heroin use and treatment utilisation is essential to inform both clinical and public health responses. We aimed to identify i) joint trajectories of heroin use and treatment utilisation, ii) predictors of joint group membership, and iii) outcomes associated with joint group membership; over 10-11 years among a cohort of Australians with heroin dependence.

METHODS

A total of 615 people with heroin dependence were recruited as part of a prospective longitudinal cohort study between 2001 and 02. This analysis focuses on 428 participants (70.1% of the original cohort) for whom complete data were available over 10-11 years.

FINDINGS

Five joint trajectory groups were identified: i) 'long-term stable' (17%: decrease in probability of heroin use alongside high treatment utilisation); ii) 'long-term success' (13%: decrease in heroin use alongside decreased treatment utilisation, until there was maintained abstinence from heroin with no treatment utilisation); iii) 'treatment failure' (12%: no decrease in heroin use alongside high treatment utilisation); iv) 'late success' (9%: gradual decrease in heroin use alongside increased treatment utilisation); and v) 'relapsed' (9%: relapse in heroin use alongside an increase and decrease in treatment utilisation). Few variables were found to predict joint group membership, but group membership was predictive of demographic, substance use and physical and mental health outcomes at 10-11 years.

INTERPRETATION

The role of treatment in recovery from heroin dependence is undeniable; however, a considerable proportion of people are able achieve and maintain abstinence without the need for ongoing treatment. An equally significant proportion will continue to use heroin despite being in long-term treatment.

FUNDING

Australian National Health and Medical Research Council.

HPV vaccine status and sexual behavior among young sexually-active women in the US: evidence from the National Health and Nutrition Examination Survey, 2007-2014

Concern has been expressed that human papillomavirus (HPV) vaccination programs might promote risky sexual behavior through mechanisms such as risk compensation, behavioral disinhibition, or perceived endorsement of sexual activity. This study assesses whether HPV vaccination status is associated with any differences in selected sexual behaviors among young sexually-active women in the US. Our dataset includes young, adult female respondents from questionnaire data collected in the National Center for Health Statistics' National Health and Nutrition Examination Survey from 2007 to 2014. The empirical approach implements a doubly robust estimation procedure, based on inverse probability of treatment weighting. For robustness, we implement several specifications for the propensity model and the outcomes model. We find no consistent association between HPV vaccination and condom usage or frequency of sex. Specifically, we find no evidence that HPV vaccination is associated with condom usage or with whether a person had sex more than 52 or more than 104 times per year. We find inconsistent evidence that HPV vaccination is associated with a person having sex more than 12 times per year. As in previous research, HPV vaccination does not appear to have a substantive effect on sexual behavior among young sexually-active women in the US.

Examination of cumulative effects of early adolescent depression on cannabis and alcohol use disorder in late adolescence in a community-based cohort

BACKGROUND AND AIMS

Although they often co-occur, the longitudinal relationship between depression and substance use disorders during adolescence remains unclear. This study estimated the effects of cumulative depression during early adolescence (ages 13-15 years) on the likelihood of cannabis use disorder (CUD) and alcohol use disorder (AUD) at age 18.

DESIGN

Prospective cohort study of youth assessed at least annually between 6th and 9th grades (~ age 12-15) and again at age 18. Marginal structural models based on a counterfactual framework that accounted for both potential fixed and time-varying confounders were used to estimate cumulative effects of depressive symptoms over early adolescence.

SETTING

The sample originated from four public middle schools in Seattle, Washington, USA.

PARTICIPANTS

The sample consisted of 521 youth (48.4% female; 44.5% were non-Hispanic White).

MEASUREMENTS

Structured in-person interviews with youth and their parents were conducted to assess diagnostic symptom counts of depression during early adolescence; diagnoses of CUD and AUD at age 18 was based the Voice-Diagnostic Interview Schedule for Children. Cumulative depression was defined as the sum of depression symptom counts from grades 7-9.

FINDINGS

The past-year prevalence of cannabis and alcohol use disorder at the age 18 study wave was 20.9 and 19.8%, respectively. A 1 standard deviation increase in cumulative depression during early adolescence was associated with a 50% higher likelihood of CUD [prevalence ratio (PR) = 1.50; 95% confidence interval (CI) = 1.07, 2.10]. Although similar in direction, there was no statistically significant association between depression and AUD (PR = 1.41; 95% CI = 0.94, 2.11). Further, there were no differences in associations according to gender.

CONCLUSIONS

Youth with more chronic or severe forms of depression during early adolescence may be at elevated risk for developing cannabis use disorder compared with otherwise similar youth who experience fewer depressive symptoms during early adolescence.

Comparison of Endovascular Stent Grafts for Abdominal Aortic Aneurysm Repair in Medicare Beneficiaries

BACKGROUND

Increased renal complications have been suggested with suprarenal stent grafts, but long-term analyses have been limited. Therefore, the purpose of this study was to evaluate the effect of endograft choice on perioperative and long-term outcomes.

METHODS

We compared Medicare beneficiaries undergoing endovascular abdominal aortic aneurysms repair from 2005 to 2008 with endografts with infrarenal fixation and a single docking limb (AneuRx, Excluder) to those with suprarenal fixation and 2 docking limbs (Zenith), or a unibody configuration (Powerlink). Propensity score weighting accounted for differences in patient characteristics among the different graft formations, and perioperative mortality, complications, and length of stay and 4-year rates of survival, rupture, and reintervention were compared.

RESULTS

Forty-six thousand one hundred seventy-one Medicare beneficiaries were identified including 11,002 (24%) with suprarenal fixation, 32,909 (71%) with infrarenal fixation, and 2,260 (5%) with a unibody graft. After propensity score weighting, there were no significant differences in patients' baseline clinical and demographic characteristics. The suprarenal fixation patients had higher rates of perioperative mortality (1.7% vs. 1.3%, P < 0.01), renal failure (6.0% vs. 4.7%, P < 0.001), and mesenteric ischemia (0.7% vs. 0.4%, P < 0.01) and longer length of stay (3.4 days vs. 3.0 days, P < 0.001) compared with patients with infrarenal fixation. Unibody grafts had higher rates of renal failure (5.9% vs. 4.7%, P < 0.001), mesenteric ischemia (1.0% vs. 0.4%, P < 0.001), and conversion to open repair (0.7% vs. 0.1%, P < 0.001) compared to those with infrarenal fixation and single docking limbs. At 4 years, mortality remained slightly higher with suprarenal compared to infrarenal fixation (30% vs. 29%, P = 0.047), although these patients had fewer conversions to open repair (0.6% vs. 0.9%, P = 0.03) and aneurysm-related reinterventions (10% vs. 12%, P < 0.01). At 4 years, unibody grafts had more aneurysm-related interventions compared to infrarenal fixation grafts (15% vs. 12%, P < 0.01) but fewer conversions to open repair (0.4% vs. 0.9%, P = 0.02). Late rupture did not differ among the groups.

CONCLUSIONS

Compared to infrarenal fixation devices, patients who underwent EVAR with suprarenal fixation had higher perioperative mortality and renal complications but fewer reinterventions including conversion, while the unibody graft had more perioperative complications and aneurysm-related reinterventions, but fewer conversions to open repair. Although these differences could be explained by selection bias, these data suggest that further comparative effectiveness analyses should be performed to understand the outcomes following EVAR with suprarenal fixation and unibody grafts.

Confounding in longitudinal studies in addiction treatment research

Background: The effectiveness of treatment for people with substance use disorders is usually examined using longitudinal cohorts. In these studies, treatment is often considered as a time-varying exposure. The aim of this commentary is to examine confounding in this context, when the confounding variable is time-invariant and when it is time-varying. Method: Types of confounding are described with examples and illustrated using path diagrams. Simulations are used to demonstrate the direction of confounding bias and the extent that it is accounted for using standard regression adjustment techniques. Results: When the confounding variable is time invariant or time varying and not influenced by prior treatment, then standard adjustment techniques are adequate to control for confounding bias, provided that in the latter scenario the time-varying form of the variable is used. When the confounder is time varying and affected by prior treatment status (i.e. it is a mediator of treatment), then standard methods of adjustment result in inconsistency. Conclusions: In longitudinal cohorts where treatment exposure is time varying, confounding is an issue which should be considered, even if treatment exposure is initially randomized. In these studies, standard methods of adjustment may result be inadequate, even when all confounders have been identified. This occurs when the confounder is also a mediator of treatment. This is a likely scenario in many studies in addiction.

Daily stressors as antecedents, correlates, and consequences of alcohol and drug use and cravings in community-based offenders

Justice-involved individuals with alcohol and drug use problems reoffend at higher rates than their nonusing counterparts, with alcohol and drug use serving as an important vector to recidivism. At the daily level, exposure to stressors may exacerbate problematic alcohol and drug use; at the individual level, prior treatment experiences may mitigate substance use as individuals adapt to and learn new coping mechanisms. We conducted a daily diary study using Interactive Voice Response technology over 14 consecutive days with 117 men on probation or parole participating in a community-based treatment program (n = 860 calls) and referred to medication-assisted treatment. Participants reported daily stressors, craving for alcohol and illegal drugs, and use of alcohol and illegal drugs 1 time each day. Results of multilevel models showed significant day-to-day fluctuation in alcohol and drug craving and use. In concurrent models, increases in daily stressors were associated with increases in cravings and use of illegal drugs. Prior treatment experience modified many of these relationships, and additional lagged models revealed that those with less treatment experience reported an increase in next-day alcohol craving when they experienced increases in stressors on the previous day compared to those with more treatment experience. Collectively, these findings highlight the importance of tailoring treatment as a function of individual differences, including prior treatment experiences, and targeting daily stressors and subsequent cravings among justice-involved adults with alcohol and drug use problems. (PsycINFO Database Record

Using Marginal Structural Modeling to Estimate the Cumulative Impact of an Unconditional Tax Credit on Self-Rated Health

In previous studies, researchers estimated short-term relationships between financial credits and health outcomes using conventional regression analyses, but they did not account for time-varying confounders affected by prior treatment (CAPTs) or the credits' cumulative impacts over time. In this study, we examined the association between total number of years of receiving New Zealand's Family Tax Credit (FTC) and self-rated health (SRH) in 6,900 working-age parents using 7 waves of New Zealand longitudinal data (2002-2009). We conducted conventional linear regression analyses, both unadjusted and adjusted for time-invariant and time-varying confounders measured at baseline, and fitted marginal structural models (MSMs) that more fully adjusted for confounders, including CAPTs. Of all participants, 5.1%-6.8% received the FTC for 1-3 years and 1.8%-3.6% for 4-7 years. In unadjusted and adjusted conventional regression analyses, each additional year of receiving the FTC was associated with 0.033 (95% confidence interval (CI): -0.047, -0.019) and 0.026 (95% CI: -0.041, -0.010) units worse SRH (on a 5-unit scale). In the MSMs, the average causal treatment effect also reflected a small decrease in SRH (unstabilized weights: β = -0.039 unit, 95% CI: -0.058, -0.020; stabilized weights: β = -0.031 unit, 95% CI: -0.050, -0.007). Cumulatively receiving the FTC marginally reduced SRH. Conventional regression analyses and MSMs produced similar estimates, suggesting little bias from CAPTs.