Peter Austin

Peter Austin
Institute for Clinical Evaluative Sciences | ICES

Doctor of Philosophy

About

1,027
Publications
149,138
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68,737
Citations
Additional affiliations
December 1999 - present
University of Toronto
Position
  • Professor (Full)

Publications

Publications (1,027)
Article
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Background Multiple imputation is frequently used to address missing data when conducting statistical analyses. There is a paucity of research into the performance of multiple imputation when the prevalence of missing data is very high. Our objective was to assess the performance of multiple imputation when estimating a logistic regression model wh...
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Background There is a paucity of the literature on the relationship between frailty and excess mortality due to the COVID-19 pandemic. Methods The entire community-dwelling adult population of Ontario, Canada, as of January 1st, 2018, was identified using the Cardiovascular Health in Ambulatory Care Research Team (CANHEART) cohort. Residents of lo...
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We used Monte Carlo simulations to compare the performance of asymptotic variance estimators to that of the bootstrap when estimating standard errors of differences in means, risk differences, and relative risks using propensity score weighting. We considered four different sets of weights: conventional inverse probability of treatment weights with...
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Background : To evaluate the association between proportion of life spent in a host nation and stroke incidence and outcomes among Canadian immigrants. Methods : We conducted a retrospective cohort study of 1.2 million adult Canadian immigrants (mean age 40 [±14.6] years, 50.5% women) who were followed between 2003 and 2018 using linked administra...
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Background Despite improved outcomes associated with ticagrelor compared with clopidogrel in acute coronary syndrome (ACS), many studies have demonstrated slow adoption of ticagrelor in the United States because of its increased cost. Less is known about how ticagrelor is adopted when there is no added cost consideration. Our objectives were to det...
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Abstract We aimed to determine whether early public health interventions in 2020 mitigated the association of sociodemographic and clinical risk factors with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We conducted a population-based cohort study of all adults in Ontario, Canada who underwent testing for SARS-CoV-2 throu...
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Background: There are limited data on the association of material deprivation with clinical care and outcomes after atrial fibrillation (AF) diagnosis in jurisdictions with universal health care. Methods: This was a population-based cohort study of individuals ≥66 years of age with first diagnosis of AF between April 1, 2007, and March 31, 2019,...
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Machine learning is increasingly being used to predict clinical outcomes. Most comparisons of different methods have been based on empirical analyses in specific datasets. We used Monte Carlo simulations to determine when machine learning methods perform better than statistical learning methods in a specific setting. We evaluated six learning metho...
Preprint
Importance The SARS-CoV-2 pandemic portends a significant increase in health care use related to post-acute COVID sequelae, but the magnitude is not known. Objective To assess the burden of post-acute health care use after a positive versus negative polymerase chain reaction (PCR) test for SARS-CoV-2. Design, Setting, and Participants Retrospecti...
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Background Emergency department visits for a psychiatric reason in the post-partum period represent an acute need for mental health care at a crucial time, but little is known about the extent of timely outpatient follow-up after these visits or how individual and intersecting social determinants of health influence this outcome. This study aimed t...
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Background: International practice guidelines make different recommendations for postoperative troponin testing to detect perioperative myocardial infarction and myocardial injury after noncardiac surgery. To gain insights into current testing patterns, we evaluated predictors of routine troponin testing after three commonly performed major noncar...
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Introduction Patients taking direct oral anticoagulants (DOACs) are increasingly managed in emergency departments (ED). It is unknown whether the risk of traumatic intracranial hemorrhage (ICH) after a head injury differs between DOACs. The objective of this study was to compare risk of ICH at the index ED visit among older adults presenting to the...
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Introduction Patients consult physicians multiple times before their incident acute heart failure (HF) hospitalization. These health care contacts may represent missed opportunities to prevent hospitalizations. Objective The objective of this study was to describe differences between sexes in health care contacts in patients ultimately hospitalize...
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Background: We evaluated the impact of publicly funded pharmacare (Ontario Health Insurance Plan [OHIP]+), which was introduced in Ontario on Jan. 1, 2018, for youth less than 25 years of age, on temporal trends in hemoglobin A1c (HbA1c, a measure of glycemic management) and the differential effect on the change in temporal trends in HbA1c accordi...
Preprint
Importance Social determinants of health (SDOH) play an important role in COVID-19 outcomes. More research is needed to quantify this relationship and understand the underlying mechanisms. Objectives To examine differential patterns in COVID-19-related mortality by area-level SDOH accounting for confounders; and to compare these patterns to those...
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SARS-CoV-2 variants of concern (VOC) are more transmissible and may have the potential for increased disease severity and decreased vaccine effectiveness. We estimated the effectiveness of BNT162b2 (Pfizer-BioNTech Comirnaty), mRNA-1273 (Moderna Spikevax) and ChAdOx1 (AstraZeneca Vaxzevria) vaccines against symptomatic SARS-CoV-2 infection and COVI...
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Objectives To identify patient, physician and geographic level factors that are associated with variation in initial stress testing strategy in patients evaluated for chest pain. Design Retrospective cohort study. Setting Population-based study of patients undergoing evaluation for chest pain in Ontario, Canada between 1 January 2011 and 31 March...
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Background No completed trials have compared carotid artery stenting (CAS) to medical therapy (MT). We examined the effectiveness of CAS compared with MT in patients with asymptomatic carotid stenosis. Methods We conducted a retrospective cohort study of 219 979 Veterans ≥65 years who received carotid imaging for asymptomatic carotid stenosis betw...
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Background There are limited data on the association of diabetes duration and glycemic control with stroke risk in atrial fibrillation (AF). Our objective was to study the association of diabetes duration and glycated hemoglobin (HbA1c) with the rate of stroke in people with diabetes and newly diagnosed AF. Methods and Results This was a populatio...
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Introduction: Comprehensive, population-based investigations of the extent and temporality of associations between common neurological and psychiatric disorders are scarce. Methods: This retrospective cohort study used linked health administrative data for Ontarians aged 40-85 years on 1 April 2002, to estimate the adjusted rate of incident deme...
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Purpose: Diabetes is associated with poorer cancer outcomes. Screening for breast and cervical cancer is recommended by clinical guidelines; however, utilization of these tests in people with diabetes has been unclear due to methodological limitations in the evidence base. We used administrative data to determine the association between diabetes an...
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Background SARS-Cov-2 infection rates are high among residents of long-term care (LTC) homes. We used machine learning to identify resident and community characteristics predictive of SARS-Cov-2 infection. Methods We linked 26 population-based health and administrative databases to identify the population of all LTC residents tested for SARS-Cov-2...
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Introduction: Telemedicine is increasingly used, but its effectiveness for stroke prevention after minor stroke or TIA is not known. We compared the care and outcomes in patients discharged from an emergency department (ED) with TIA or stroke before and after the implementation of telemedicine stroke prevention clinics in Ontario, Canada. We hypoth...
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Objective Antipsychotic reduction in nursing homes has been a focus of research and policy attention for several decades; however, there is evidence that these initiatives may have had unintended consequences, such as medication substitution and changes in diagnosis coding. Our objectives were to describe temporal changes in the use of antipsychoti...
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Background The Fine-Gray subdistribution hazard model is frequently used in the cardiovascular literature to estimate subject-specific probabilities of the occurrence of an event of interest over time in the presence of competing risks. A little-known limitation of this approach is that, for some subjects and for some time points, the sum of the su...
Preprint
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Background The incidence of SARS-CoV-2 infection, including among those who have received 2 doses of COVID-19 vaccines, has increased substantially since Omicron was first identified in the province of Ontario, Canada. Methods Applying the test-negative design to linked provincial data, we estimated vaccine effectiveness against infection (irrespec...
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Thrombocytosis is associated with cancer progression and death for many cancer types. It is unclear if platelet count is also associated with cancer survival. We conducted a cohort study of 112,231 adults in Ontario with a diagnosis of cancer between January 2007 and December 2016. We included patients who had a complete blood count (CBC) completed...
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Background Assessing calibration—the agreement between estimated risk and observed proportions—is an important component of deriving and validating clinical prediction models. Methods for assessing the calibration of prognostic models for use with competing risk data have received little attention. Methods We propose a method for graphically asses...
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Importance Self-harm and deaths among adolescents and young adults are notably related to drug poisonings and suicide. With the emergence of the COVID-19 pandemic, there are projections about a greater likelihood of such events arising among adolescents and young adults. Objective To evaluate the risk of self-harm, overdose, and all-cause mortalit...
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IMPORTANCE Persons with dementia and Parkinson disease (PD) are vulnerable to disruptions in health care and services. OBJECTIVE To examine changes in health service use among community-dwelling persons with dementia, persons with PD, and older adults without neurodegenerative disease during the first wave of the COVID-19 pandemic. DESIGN, SETTING,...
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Importance Individuals with cancer often have an elevated platelet count at the time of diagnosis. The extent to which an elevated platelet count is an indicator of cancer is unclear. Objective To evaluate the association of an elevated platelet count with a cancer diagnosis. Design, Setting, and Participants This nested case-control study includ...
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Background Evidence on the cardiovascular health effects of cannabis use is limited. We designed a prospective cohort study of older Veterans (66 to 68 years) with coronary artery disease (CAD) to understand the cardiovascular consequences of cannabis use. We describe the cohort construction, baseline characteristics, and health behaviors that were...
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Importance Deferred diabetic foot screening and delays in timely care of acute foot complications during the COVID-19 pandemic may have contributed to an increase in limb loss. Objective To evaluate the association of the COVID-19 pandemic with diabetes-related care measures, foot complications, and amputation. Design, Setting, and Participants T...
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Objectives During the COVID-19 pandemic wearing a mask in public has been recommended in some settings and mandated in others. How often this advice is followed, how well, and whether it inadvertently leads to more disease transmission opportunities due to a combination of improper use and physical distancing lapses is unknown. Design Cross-sectio...
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Introduction Anticoagulation may improve outcomes in patients with COVID-19 when started early in the course of illness. Materials and methods This was a population-based cohort study using linked administrative datasets of outpatients aged ≥65 years old testing positive for SARS-CoV-2 between January 1 and December 31, 2020 in Ontario, Canada. Th...
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Objective We sought to compare the long-term outcomes of multi-arterial graft (MAG) coronary artery bypass grafting (CABG) vs percutaneous coronary intervention (PCI) with second generation drug-eluting stents (DES) to treat stable multivessel coronary artery disease. Methods Multicenter population-based retrospective analysis of all residents of...
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Abstract Background Neurological disorders and mental health conditions, including mood/anxiety disorders, are a leading cause of disability and healthcare use. These disorders have shared risk factors and commonly co-occur in older adults. Mood/anxiety disorders are often under-diagnosed and under-treated among those with neurological disorders, p...
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Little has been quantified, at a population‐level, about the magnitude of heath service disruption to persons living with dementia in community settings during the COVID‐19 pandemic. Sustained access to health care services is particularly important for persons with dementia and other neurodegenerative diseases as they are vulnerable to decline. He...
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Background: Coronary artery bypass grafting (CABG) and surgical aortic valve replacement (AVR) are the 2 most common cardiac surgery procedures in North America. We derived and externally validated clinical models to estimate the likelihood of death within 30 days of CABG, AVR or combined CABG + AVR. Methods: We obtained data from the CorHealth...
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The Cox proportional hazards model is used extensively in clinical and epidemiological research. A key assumption of this model is that of proportional hazards. A variable satisfies the proportional hazards assumption if the effect of that variable on the hazard function is constant over time. When the proportional hazards assumption is violated fo...
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Introduction: Dual antiplatelet therapy with P2Y12 inhibitors (P2Y12i) and ASA reduce cardiac events after acute coronary syndrome (ACS). Use has shifted from clopidogrel to ticagrelor, a more potent P2Y12i with higher bleeding risk, dosed twice rather than once daily. As these factors may impact adherence, a better understanding of adherence patte...
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Introduction: The association between CAD severity and long-term outcomes in patients admitted with acute HF has not been determined. We characterized the angiographic burden of CAD in patients with acute HF and determined the association between CAD severity and mortality and readmission outcomes. Methods: In a multicenter registry of 70 hospitals...
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Introduction: While sodium glucose cotransporter 2 inhibitors (SGLT2i) improve cardiovascular outcomes in type 2 diabetes (T2D) and cardiovascular disease (CVD), their uptake in clinical practice in this population is unclear. Therefore, we evaluated trends in SGLT2i use and identified predictors of use in patients with concomitant T2D and CVD. Met...
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Background We evaluated whether immigration status modified the association between sex and the quality of primary cardiovascular disease prevention in Ontario, Canada. Methods and Results We used a population‐based administrative database‐derived cohort of community‐dwelling adults (aged ≥40 years) without prior cardiovascular disease residing in...
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Study Objective To evaluate the opioid prescribing practices of resident trainees compared to academic and community staff surgeons following elective hysterectomy. We also sought to identify surgeon characteristics associated with high-dose opioid prescriptions. Design A retrospective population-based cohort study. Setting We used linked adminis...
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Objectives To evaluate the association between immigration status and all-cause mortality in different disease cohorts, and the impact of loss to follow-up on the observed associations. Design Population-based retrospective cohort study using linked administrative health data in Ontario, Canada. Setting We followed adults with a first-ever diagno...
Article
Background This study aimed to assess whether surgical case volume for lateral neck dissection has an impact on the survival of patients who have well-differentiated thyroid cancer (WDTC) with lateral cervical node metastases. The authors used a population-based cohort study design.Methods The study cohort consisted of WDTC patients in Ontario Cana...
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Background The relationship between health care utilization and outcomes in patients with atrial fibrillation is unknown. The objective of this study was to investigate whether cardiologists’ billing amounts in a fee‐for‐service environment are associated with better patient‐level clinical outcomes. Methods and Results A retrospective cohort study...
Article
Background: Intracranial hemorrhage (ICH) after head injury is a concern among older adult patients on anticoagulation. We evaluated the risk of ICH after an emergency department visit for head injury among patients 65 years and older taking warfarin or a direct oral anticoagulant (DOAC) compared with patients not taking anticoagulants. We also ev...
Article
Background There are limited data on the association between cholesterol levels and stroke risk in atrial fibrillation (AF). Objective To quantify the association of stroke rate in AF with low-density lipoprotein (LDL) levels and statin use. Methods Using linked administrative databases in Ontario, Canada, we conducted a population-based retrospe...
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PurposeCanadian breast cancer screening guidelines state that mammography screening for women 40–49 should be individualized based on risk assessment and preferences. This retrospective cohort study describes the frequency of screening in women aged 40–49 and identifies patient and provider-level associations with screening.Methods Administrative d...
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Objective To determine the risk factors associated with late mortality or complications (Thoracoabdominal aortic Aneurysm Life-altering Events (TALE): composite of mortality, permanent paraplegia, permanent dialysis, and stroke) in patients undergoing endovascular or open thoracoabdominal aortic aneurysm (TAAA) repair. Methods Population-based stu...
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BACKGROUND Anthracycline and trastuzumab are important systemic therapies for early breast cancer (EBC) but are associated with an increased incidence of heart failure (HF). However, the prognosis of HF associated with anthracyclines and/or trastuzumab for EBC is not well-elucidated. Our objective was to describe the characteristics and prognosis o...
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BACKGROUND Cardiovascular disease is a leading cause of death and disability globally. Cardiovascular disease incidence varies by immigration status and sex. Sex differences in the quality of primary cardiovascular preventive care have been described, but whether these differences vary by immigration status is less understood. Intersectionality the...
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BACKGROUND The gender pay gap in medicine is well documented. Frequently cited drivers of gender-based billings disparities are women entering lower-remunerated specialties and fewer hours worked. To date, there has not been a population-based analysis of the gender pay gap and gender-based practice differences in a highly remunerated specialty lik...
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Background It is not known if initial reductions in hospitalization for stroke and myocardial infarction early during the coronavirus disease–2019 pandemic were followed by subsequent increases. We describe the rates of emergency department visits for stroke and myocardial infarction through the pandemic phases. Methods We used linked administrati...
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Purpose: Randomized trials from Africa demonstrate that circumcision reduces the risk of acquiring HIV among males. However, few studies have examined this association in Western populations. We sought to evaluate the association between circumcision and the risk of acquiring HIV among males from Ontario, Canada. Materials and methods: We conduc...
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Propensity score weighting is increasingly being used in observational studies to estimate the effects of treatments. The use of such weights induces a within-person homogeneity in outcomes that must be accounted for when estimating the variance of the estimated treatment effect. Knowledge of the variance inflation factor (VIF), which describes the...
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Propensity score-based analysis is increasingly being used in observational studies to estimate the effects of treatments, interventions, and exposures. We introduce the concept of the propensity score and how it can be used in observational research. We describe four different ways of using the propensity score: matching on the propensity score, i...