Christoffer Dharma

University of Toronto | U of T

Objectives This study examined how six Canadian provinces (Alberta, British Columbia, Manitoba, Nova Scotia, Ontario, Quebec) adapted guidelines from the National Advisory Committee on Immunization to prioritize COVID-19 vaccines equitably for five key populations at high risk: Black communities; First Nations, Inuit, and Métis populations; non-med...

Sexual minority populations experience a higher burden of mental health and substance use/misuse conditions than heterosexual comparators—a health inequality that has predominantly been attributed to forms of minority stress experienced by the former group. Sexual minority-affirming legislative and policy advances, as well as improvements in social...

The prevalence and relative disparities of mental health outcomes and well-being indicators are often inconsistent across studies of sexual minority men (SMM) due to selection biases in community-based surveys (nonprobability sample), as well as misclassification biases in population-based surveys where some SMM often conceal their sexual orientati...

Transgender women of color (TWOC) experience high rates of police violence and victimization compared to other sexual and gender minority groups, as well as compared to other White transgender and cisgender women. While past studies have demonstrated how frequent police harassment is associated with higher psychological distress, the effect of neig...

Background Adverse childhood experiences (ACE) are important predictors of mental health outcomes in adulthood. However, commonly used ACE measures such as the Behavioural Risk Factor Surveillance System (BRFSS) have not been validated among Black sexually minoritized men (SMM) nor transgender women (TW), whom are known to have higher rates of ACE...

Introduction: There is a need to reflect on the COVID-19 vaccine distribution across Canada and the extent to which they considered equity-deserving populations. This paper examined and compared strategies implemented by six Canadian provinces to increase access and promote the uptake of COVID-19 vaccines among selected priority populations. We als...

Background Substance use is increasing among sexual and gender minority youth (SGMY). This increase may be due to changes in social norms and socialisation, or due to SGMY exploring the potential therapeutic value of drugs such as psychedelics. We identified predictors of psychedelics, MDMA and ketamine use. Methods Data were obtained from 1414 SG...

When the COVID-19 virus rapidly spread across Canada in 2020, provinces and territories implemented various vaccine rollout plans. This commentary shares the experience of an implementation science research group conducting an equity-focused evaluation of the vaccine rollout plans of six Canadian provinces through a literature review and key inform...

There is a lack of rigorous methodological development for descriptive epidemiology, where the goal is to describe and identify the most important associations with an outcome given a large set of potential predictors. This has often led to the Table 2 fallacy, where one presents the coefficient estimates for all covariates from a single multivaria...

Background: Patients with thrombophilia are underrepresented in studies evaluating outcomes after closure of patent foramen ovale (PFO). Real-world data on long term outcomes in this population are very limited. Objectives: This study compared outcomes in patients with and without thrombophilia undergoing PFO closure, using data from a large, cl...

External stressors can erode relationship quality, though little is known about what can mitigate these effects. We examined whether COVID-related stressors were associated with lower relationship quality, and whether perceived partner responsiveness—the extent to which people believe their partner understands, validates, and cares for them—buffers...

Background: Social geography plays an important role in transmission of sexually transmitted infections (STIs) among men who have sex with men (MSMs). Previous qualitative work had identified seven "geosexual archetypes", each with distinct travel patterns for sex and potentially important differences in STI rates. The objective of this paper was...

Background: Systemic administration of heparin is widely used in patients undergoing open elective abdominal aortic aneurysm (AAA) repair. However, no clear consensus exists in the use of intraoperative heparin during open ruptured AAA (rAAA) repair. In this study, we assessed the safety of intravenous heparin administration in patients undergoing...

Purpose: There is a lack of longitudinal studies that examine changes in mental health among 2SLGBTQ+ youth during the COVID-19 pandemic. Hence, using a Canadian cohort of young 2SLGBTQ+ (16-29 years old), weidentified the factors that predicted increases in self-reported depressive symptoms scores (n = 882) and those that predicted incidence in di...

Importance Despite advances in asthma therapeutics, the burden remains highest in preschool children; therefore, it is critical to identify primary care tools that distinguish preschool children at high risk for burdensome disease for further evaluation. Current asthma prediction tools, such as the modified Asthma Predictive Index (mAPI), require i...

Background Patent foramen ovale (PFO) is a congenital heart defect associated with an increased risk of cryptogenic stroke. We aimed to evaluate real-world outcomes of adult patients undergoing transcatheter PFO closure with the Amplatzer PFO Occluder. Methods In this single centre, retrospective cohort study, we linked a detailed clinical registr...

e18840 Background: This Canadian study analyzes real-world data to estimate phase-specific costs and health care resource utilization for patients with diffuse large B-cell lymphoma (DLBCL). Methods: A cohort of adult patients diagnosed with DLBCL were identified between 2003-2014 from the Ontario Cancer Registry (OCR) and linked to treatment data...

Introduction: Several androgen deprivation therapy (ADT) medications are available for treating advanced prostate cancer with roughly equivalent oncological efficacy and tolerability. We investigated the proportion of physicians who predominantly prescribe one type of ADT drug ("mono-prescriber") and assessed characteristics associated with prescr...

The COVID-19 pandemic has touched many aspects of people’s lives around the world, including their romantic relationships. While media outlets have reported that the pandemic is difficult for couples, empirical evidence is needed to test these claims and understand why this may be. In two highly powered studies ( N = 3271) using repeated measure an...

External stressors can erode relationship quality, though little is known about what can mitigate these effects. We examined whether COVID-related stressors were associated with lower relationship quality, and whether perceived partner responsiveness—the extent to which people believe their partner understands, validates, and cares for them—buffers...

The COVID-19 pandemic has touched many aspects of people’s lives around the world, including their romantic relationships. While media outlets have reported that the pandemic is difficult for couples, empirical evidence is needed to test these claims and understand why this may be. In two highly powered studies (N = 3,271) using repeated measure an...

Centre for Vaccine Preventable Diseases (Dalla Lana School of Public Health, University of Toronto) seminar series presentation

Background Functional tricuspid regurgitation (TR) is a common pathophysiological condition in adults with secundum atrial septal defect (ASD). The aim of this study was to evaluate long-term outcomes following transcatheter ASD closure, which have not been well studied among patients with significant TR. Methods We reviewed consecutive adult pati...

Purpose: Phase-III RCT evidence suggests intermittent ADT (IADT) is not significantly inferior to continuous ADT for prostate cancer (PC) patients. However, clinical practice and guidelines differ in their recommendations. We evaluate real-world utilization and practice patterns of IADT. Materials and methods: Ontario men ≥65 years with PC who i...

Importance Intraoperative anesthesiology care is crucial to high-quality surgical care. The clinical expertise and experience of anesthesiologists may decrease the risk of adverse outcomes. Objective To examine the association between anesthesiologist volume and short-term postoperative outcomes for complex gastrointestinal (GI) cancer surgery. D...

Objectives: The long-term outcomes after transcatheter closure of atrial septal defects (ASD) in adults are reported and compared between age groups and against population control patients. Background: ASD is the second most common lesion in congenital heart disease. Comprehensive data on long-term outcomes after ASD closure are limited. Method...

New guidelines for peanut allergy prevention in high-risk infants recommend introducing peanut during infancy but do not address breastfeeding or maternal peanut consumption. We assessed the independent and combined association of these factors with peanut sensitization in the general population CHILD birth cohort ( N = 2759 mother–child dyads). Mo...

Background While randomized clinical trials have demonstrated the superiority of coronary artery bypass grafting (CABG) over percutaneous coronary intervention (PCI) in patients with diabetes and multivessel coronary artery disease (CAD), there remains a paucity of observational evidence comparing these two modalities. Methods Clinical and adminis...

Background There remains a paucity of real-world observational evidence comparing percutaneous coronary intervention (PCI) with coronary artery bypass grafting (CABG) in patients with diabetes and multivessel coronary artery disease (CAD). Objectives This study compared early and long-term outcomes of PCI versus CABG in patients with diabetes. Me...

Objectives: Cholinesterase inhibitors (ChEIs) and memantine are approved for Alzheimer disease in Canada. Regional drug reimbursement policies are associated with cross-provincial variation in ChEI use, but it is unclear how these policies influence predictors of use. Using standardized data from two provinces with differing policies, we compared r...

Background: Comprehensive longitudinal studies are important for understanding the complex risk factors, pathways, exposures and interactions that lead to the development and persistence of asthma. We aimed to examine associations between use of household cleaning products in early life and childhood respiratory and allergic disease using data fro...

Objectives: The aim of this study was to compare early and late outcomes between redo surgical aortic valve replacement (AVR) and valve-in-valve (ViV) transcatheter AVR. Background: Published studies to date comparing redo surgical AVR (RS) with ViV transcatheter AVR for failed biological prostheses have been small and limited to early outcomes....

Background While the gold standard for the management of failed previous biological prosthesis was redo surgical aortic valve replacement (SAVR), valve-in-valve (ViV) transcatheter AVR (TAVR) has emerged as a less invasive option. Published studies comparing the two techniques have been small and limited to early outcomes. Herein, we compare early...

Objective: The safety and efficacy of aortic root enlargement (ARE) at the time of aortic valve replacement (AVR) remains unknown. The objective of this multicenter study was to compare AVR with ARE to AVR for early and late mortality and secondary safety outcomes. Methods: Clinical and administrative databases in Ontario, Canada, were linked to...

Polyamory is the practice of having multiple emotionally close relationships that may or may not be sexual. Research concerning polyamory has just begun to determine how relationships among partners in polyamorous arrangements may vary. Most of the research assessing perceptions of polyamorous partners has focused on primary–secondary configuration...

Randomized clinical trials demonstrate that treating vitamin B12 (cobalamin, or hereinafter B12) deficiency with oral supplementation substantially increases serum B12 levels compared with intramuscular injections, with no difference in hematologic or neuropsychiatric outcomes.¹ Despite this, some primary care physicians still inappropriately admin...

Few sexual health measures have been validated for transgender (trans) populations. Condom/barrier self-efficacy and sexual body image worries are interrelated constructs that may contribute to enhanced and poor sexual health, respectively. We report on the development and initial validation of trans-specific scales designed to measure these constr...

Objectives. To identify trajectory patterns of maternal depressive symptoms and perceived stress from midpregnancy to 2 years postpartum and determine relationships with selected sociodemographic factors including income, education, immigration, and postpartum employment. Methods. Pregnant women (n = 3307) recruited from the general population in 4...

Romantic partners provide both erotic and nurturing experiences, though these may emerge more strongly in different phases of a relationship. Unlike individuals in monogamous relationships, those in polyamorous relationships can pursue multiple romantic relationships simultaneously, potentially allowing them to experience higher levels of eroticism...

Romantic partners provide both erotic and nurturing experiences, though these may emerge more strongly in different phases of a relationship. Unlike individuals in monogamous relationships, those in polyamorous relationships can pursue multiple romantic relationships simultaneously, potentially allowing them to experience higher levels of eroticism...

Introduction B12 deficiency can lead to multiple complications, including severe pancytopenia, spinal cord demyelination, and cognitive dysfunction. Randomized controlled trials have demonstrated oral B12 supplementation is as effective as parenteral B12 administration in improving hematologic abnormalities and raising B12 levels. Despite this evid...

Background Persisting atopic dermatitis (AD) is known to be associated with more serious allergic diseases at later ages; however, making an accurate diagnosis during infancy is challenging. We assessed the diagnostic performance of questionnaire‐based AD measures with criteria‐based in‐person clinical assessments at age 1 year and evaluated the ab...

Polyamory is the practice of having multiple emotionally-close relationships that may or may not be sexual. Research concerning polyamory has just begun to determine how relationships among partners in polyamorous arrangements may vary. Most of the research assessing perceptions of polyamorous partners has focused on primary-secondary configuration...

Objective: Past cross-sectional studies have reported that mothers from ethnic minorities experience higher levels of prenatal and post-partum psychosocial distress compared with mothers from ethnic majorities. However, no studies have examined how the pattern varies longitudinally in a Canadian population of heterogeneous ethnicity. Methods: We...

Research on polyamorous relationships has increased substantially over the past decade. This work has documented how polyamory is practiced and why individuals might pursue such arrangements. However, there is a lack of a systematic investigation of who is in polyamorous relationships and how they might differ from individuals in monogamous relatio...

Background: The atopic march describes the progression from atopic dermatitis during infancy to asthma and allergic rhinitis in later childhood. In a Canadian birth cohort we investigated whether concomitant allergic sensitization enhances subsequent development of these allergic diseases at age 3 years. Methods: Children completed skin prick te...

Background: The effect of infant feeding practices on the development of food allergy remains controversial. We examined the relationship between timing and patterns of food introduction and sensitization to foods at age 1 year in the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort study. Methods: Nutrition questionnaire da...

Given that an estimated 0.6% of the U.S. population is transgender (trans) and that large health disparities for this population have been documented, government and research organizations are increasingly expanding measures of sex/gender to be trans inclusive. Options suggested for trans community surveys, such as expansive check-all-that-apply ge...

SAS coding for multidimensional test measure. (PDF)

SAS coding for two-step test measure. (PDF)

SAS coding for new Multidimensional Sex/Gender Measure. (PDF)

OBJECTIVE: Public health research on inequalities in Canada depends heavily on population data sets such as the Canadian Community Health Survey. While sexual orientation has three dimensions – identity, behaviour and attraction – Statistics Canada and public health agencies assess sexual orientation with a single questionnaire item on identity, de...