Health Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

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Using latent profile analysis to examine associations between gestational chemical mixtures and child neurodevelopment

Author: 
Date created: 
2021-08-03
Abstract: 

In this study, we introduced Latent Profile Analysis (LPA) as a novel technique for studying gestational chemical mixtures. Using data from the Maternal-Infant Research on Environmental Chemicals Study, a longitudinal birth cohort study of pregnant Canadian women and their children, we examined the relationship between 30 gestational biomarkers and Verbal IQ, Performance IQ, and Full-Scale IQ. We generated five latent profiles: A Reference profile, a High Level profile, a Low Level profile, a High Organophosphate Pesticides profile, and a Smoking Chemicals profile. Multiple regression analysis showed strong negative associations between the Smoking Chemicals profile and IQ scores. We also found positive associations between the Low Level profile and IQ, and a negative association between the High Level profile and Verbal IQ. However, all 95% confidence intervals spanned the null. After conducting sensitivity analysis comparing LPA with k-means clustering, we concluded that LPA is a promising alternative to other clustering methods.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Lawrence McCandless
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) M.Sc.

Causal mediation analysis with a partially missing mediator: exploring the effect of portable air purifier use during pregnancy on infant birth weight

Author: 
Date created: 
2021-08-26
Abstract: 

Mediation analysis examines the exposure-outcome association that acts through an intermediate variable. However, mediation analysis becomes challenging when data have missing values. Although methods exist to deal with missing data and mediation analysis independently, few studies have examined how to combine the approaches, specifically, how to pool the mediation analysis results across a series of imputed datasets and compute confidence intervals for target parameters. We propose a new technique that combines multiple imputation with maximum likelihood estimation. Using computer simulations, we compare the performance of our proposed approach with a traditional bootstrap approach. Our method performs well and is more computationally efficient than other resampling methods. We apply the new method to randomized trial data on the role of cadmium exposure in mediating the effects of an environmental health intervention on birth weight.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Lawrence McCandless
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) M.Sc.

Immigration, sex/gender, and patterns of access to primary care in Canada

Date created: 
2021-04-19
Abstract: 

Background: Primary care provides entry to the Canadian health care system, subsequent coordination, and integration of all levels of care. People who have immigrated to Canada may experience difficulties accessing primary care, but gaps in conceptualization and operationalization of “access” has resulted in conflicting results and uncertain policy implications. How the interaction of immigration and sex/gender impacts patterns of access to primary care has also been understudied. Objectives: The study examines how patterns of access to primary care differ between immigration groups and how sex/gender and immigration interact to shape patterns of access. Methods: I used 2015-2018 Canadian Community Health Survey Data to describe patterns of access to primary care among adult residents of Canada (age 18+), categorizing variables related to primary care access by stages of the Levesque framework including perception and desire for care, healthcare seeking, reaching and utilization. I compared patterns of access between recent immigrants (people in Canada for less than 10 years, including both temporary migrants and permanent immigrants), long-term immigrants (in Canada 10+ years), and non-immigrants (people who were born in Canada). I used logistic regression models to calculate adjusted and unadjusted odds estimates for each variable related to primary care, and to explore interaction effects of sex/gender and immigration. Results: Patterns of access among recent immigrants significantly differed from long-term and non-immigrants with respect to perception and desire for care, seeking and utilization. Similar patterns were observed between long-term and non-immigrants except at the utilization stage. Interaction effects of gender and immigration were more pronounced in earlier stages of health care seeking but not reaching nor utilization. Conclusion: The Lévesque framework of health services use was important in highlighting differences among immigration groups along the whole process of obtaining care. Interventions focused on improving approachability and acceptability of services and addressing gendered barriers, especially among recent male immigrants, are important to improve access to primary care.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Ruth Lavergne
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) M.Sc.

Priority setting for the overdose crisis: Challenges and opportunities for peer engagement in British Columbia

Author: 
Date created: 
2020-08-25
Abstract: 

In recent years, decision-makers in BC have engaged people who use(d) drugs (PWUD) and the general public for their input on strategic directions regarding the overdose crisis. Given the oft-politicized nature of substance use, it is important for the response to centre around people with lived experience and to be grounded by the best available evidence. By engaging PWUD or “peers” as essential partners, the resulting policies and services may better reflect the community’s needs. Meaningful engagement can be challenging due to stigma and a multitude of systemic barriers. Special considerations must be taken to ensure participatory processes are inclusive and ethical. BC’s worsening overdose crisis demands that we reevaluate our drug policies and spending priorities across health and other social sectors. PWUD have identified several key priority areas, including expansion of harm reduction, controlled pharmaceutical prescribing, and drug decriminalization, some of which have ignited considerable debate among stakeholders.

Document type: 
Graduating extended essay / Research project
File(s): 
Supervisor(s): 
Kanna Hayashi
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Project) M.P.H.

Increased risk of severe infections and mortality in patients with newly diagnosed systemic lupus erythematosus: A population-based study

Author: 
Date created: 
2021-01-25
Abstract: 

Systemic lupus erythematosus (SLE) is a chronic disease with a broad spectrum of clinical manifestations and infections are a leading cause of morbidity and premature mortality in patients with SLE. Findings from previous studies may be limited because of small sample sizes and using prevalent cohorts. To evaluate the risk of severe infection and infection-related mortality among patients with newly diagnosed SLE. We conducted an age- and gender- matched cohort study of all patients with incident SLE using administrative health data from British Columbia, Canada. Primary outcome was the first severe infection after SLE onset. Secondary outcomes were total number of severe infections and infection-related mortality. Multivariable Cox proportional hazard and Poisson models were used to evaluate the association of SLE with the outcomes, adjusting for confounders. The findings suggest SLE is associated with increased risks of first severe infection, a greater total number of severe infections and infection-related mortality.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Hui Xie
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) M.Sc.

Patterns of health service use among people experiencing homelessness and mental illness in British Columbia

Author: 
Date created: 
2021-04-16
Abstract: 

Background: The burden of illness faced by people experiencing both homelessness and mental illness is staggering. When the needs of this population go unmet, it is often the healthcare system that is criticized. The aim of this thesis was to examine patterns of medical service use among people experiencing homelessness and mental illness, and to identify factors associated with high-levels of use, health outcomes and opportunities for intervention. It was hypothesized that people with the highest objective needs would access more medical services and that those who access care in a timely and continuous fashion would have better outcomes, including lower risk of hospitalization. Methods: Data were drawn from both the baseline interviews of Vancouver At Home (VAH) study participants and the Inter-Ministry Research Initiative database. All analyses were retrospective using both self-report and administrative data to examine factors associated with low vs. high health service use, continuity of care following hospitalization, and timeliness of community-based medical service use following detention in provincial custody. Results: Among VAH participants, we found that those with lower assessed need were accessing more health services that those with higher needs (i.e., schizophrenia). When continuity of care was examined, we found that our sample was accessing community-based outpatient services in both a timely and ongoing manner, however, it was not conferring a protective benefit against rehospitalization. Finally, when studying the impact of timely community medical service use following release from provincial custody, we found that those who accessed services in both a timely and continuous manner were more likely to be hospitalized than those not using services in this manner. Discussion: These findings highlighted the overwhelming burden of illness among people experiencing homelessness and mental illness. Contrary to our hypotheses, those with the greatest needs were not accessing the most health services, and for those who did access services frequently, these contacts did not offer protection against further negative health outcomes including hospitalization. Collectively these findings suggest looking beyond the healthcare system and underscore the importance of structural and systemic failings within our social, justice and healthcare systems as perpetuating the morbidity within this population.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Julian Somers
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) Ph.D.

Factors associated with housing stability and criminal convictions among people experiencing homelessness and serious mental illness: Results from a Housing First study

Date created: 
2021-05-25
Abstract: 

Background: Housing First (HF) facilitates immediate access to independent housing with community-based supports for people experiencing homelessness and serious mental illness (PEHSMI). Despite positive outcomes associated with HF, studies have infrequently investigated factors that are associated with adverse outcomes once in HF. This thesis investigates factors which hinder housing stability following randomization to HF and factors associated with criminal convictions prior to and following randomization to HF. Methods: Three investigations were conducted using data from the Vancouver At Home study, which contains two randomized controlled trials each involving randomization to HF vs. treatment as usual (TAU) among PEHSMI. Using self-reported data, the first investigation examined the effect of experiencing homelessness in childhood or youth on housing stability (≥90% of days stably housed) after receiving HF (TAU excluded). The second investigation retrospectively examined factors associated with criminal convictions during the five-year period preceding baseline. The third investigation examined factors associated with criminal convictions after receiving HF (TAU excluded). Provincial administrative data were combined with self-reported baseline data for the second and third investigations. Results: 1) Among participants randomized to HF (n=297), those who had experienced homelessness in childhood or youth had significantly lower odds of housing stability. 2) Prior to study baseline, seven variables were significantly associated with criminal convictions among participants (n=425), such as drug dependence, psychiatric hospitalization, and irregular frequency of social assistance payments (vs. regular). 3) Following receipt of HF (n=255), five variables were significantly associated with criminal convictions, including daily drug use, daily alcohol use, and having received addictions counselling among others. Conclusions: Results underscore social marginalization as contributing to poorer housing stability in HF and criminal convictions while in HF and prior to enrollment among PEHSMI. Further supports are needed to facilitate improvements for a greater proportion of HF clients. HF providers may be able to identify clients with additional support needs related to housing stability and criminal convictions by asking about the factors found to be significant in analyses.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Julian Somers
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) Ph.D.

Discrimination at work and symptoms of mental disorders among nurses in British Columbia

Date created: 
2020-10-14
Abstract: 

Nurses belonging to equity-seeking groups, including people of colour, Indigenous people, people with disabilities, and people identifying as 2SLGBTQIA+, face barriers to opportunities and resources, and might more frequently experience workplace discrimination. Whether these experiences are associated with adverse mental health outcomes is unknown. This study examines factors associated with workplace discrimination and relationships between discrimination and mental health outcomes, using survey data from nurses in British Columbia, Canada. Using logistic regression, I investigated relationships between workplace discrimination and symptoms of mental disorders, adjusting for personal and work/role characteristics. Of 4545 respondents, 12.5% reported experiencing discrimination, rising to between 19.6% and 24.4% among those who identify with equity-seeking groups. Overall, 45.8% of nurses reported symptoms of post-traumatic stress disorder, 28.1% reported symptoms of anxiety, and 31.1% reported symptoms of depression. Nurses reporting workplace discrimination were more than twice as likely to report symptoms of mental disorders, with similar results across mental disorders. Experiences of discrimination in the workplace are common for nurses in BC, and symptoms of post-traumatic stress disorder, anxiety, and depression are prevalent in this population. Worker psychological health and safety is often treated as an individual issue and responsibility, but we must instead consider how it is related to working conditions both embedded in, and reflecting, societal inequalities.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Ruth Lavergne
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) M.Sc.

Social and structural contexts of the overdose crisis: An ethnography of overdose risk among structurally vulnerable women who use drugs in Vancouver, Canada

Author: 
Date created: 
2020-01-08
Abstract: 

Background: North America’s overdose crisis is driven by illicitly-manufactured fentanyl and fentanyl-adulterated drugs. Vancouver’s Downtown Eastside neighborhood in Canada is one of North America’s overdose epicenters. Notably, the majority of overdose deaths in Vancouver are occurring in indoor environments, including single room accommodations (SRA) housing. While there is an awareness of the role social, structural, and environmental factors in producing harm among people who use drugs (PWUD), we do not fully understand how social-structural forces (e.g. housing models, social norms) shape overdose risk for women who use drugs (WWUD). This dissertation seeks to address this gap by examining how contextual factors operating in a street-based drug scene create variegated overdose risk for WWUD. Methods: This dissertation draws on ethnographic research conducted with WWUD living in SRAs in Vancouver’s Downtown Eastside from May 2017 to December 2018. Data include in-depth baseline and follow-up interviews, and approximately 100 hours of observational fieldwork in SRAs and neighborhood areas. Analysis drew on an intersectional risk environment approach that was developed and then applied to the data to characterize social-structural dynamics shaping overdose risk for WWUD. Results: Findings underscored how normalized violence against WWUD in the drug scene shaped the social and spatial relations of women, and acted as a driver of overdose risk. First, women challenged gendered power dynamics through embodied drug use practices and using drugs alone. Second, WWUD experienced operational and social environmental barriers that minimized their utilization of low-threshold overdose-related interventions in SRAs, thereby increasing risk of fatal overdose. Finally, WWUD experienced burnout related to care-taking and paid labor responsibilities (e.g. peer overdose response), which led them to use drugs alone to cope. Conclusion: These findings demonstrate how gendered power dynamics operating within a drug scene setting overlapped with social (e.g. stigmatization, gender inequities), structural (e.g. prohibition of smoking in overdose-related interventions), and environmental factors to shape fatal overdose risk for WWUD. These findings underscore the need for wider structural transformations to mitigate morbidity and mortality for WWUD. Modifying and scaling up overdose prevention interventions in the community and within SRAs to make them more accessible to women is also imperative.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Kanna Hayashi
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) Ph.D.

The whole systems approach to obesity and non-communicable diseases: Implications for research, policy and practice

Author: 
Date created: 
2019-12-10
Abstract: 

Obesity and non-communicable diseases (NCDs), significant threats to population health, are widely understood to be embedded in complex systems of interdependent causal factors. As such, researchers, policymakers and practitioners have become increasingly interested in systems-wide approaches that have the potential to reduce the burden of these diseases. Outcomes of this trend include the development and application of new systems science methods, and a turn towards multi-sectoral collaborative engagement as a key directive for influencing systems. This dissertation explores these aspects of the whole systems approach to obesity and NCDs through three original research papers. In the first, a novel systems science framework is employed to analyze recommendations drawn from 12 documents aimed at influencing obesity planning. Results show that many of the documents focus on changing the determinants of energy imbalance and lack planning at higher levels of system function, such as interconnections between system elements and goal setting. This paper demonstrates the utility of systems science frameworks for introducing systems thinking into policy-level planning in a manner accessible to public health stakeholders. The second and third papers turn to the subject of multi-sectoral partnerships. The first of these represents a review of the role of public health partnerships with the private sector in addressing obesity and NCDs. Contemporary challenges around working with the food and beverage sector are considered through a systems-informed lens that pushes traditional thinking about conflict of interest and the role of monitoring and evaluation activities related to partnership engagement. The following chapter presents an exploratory qualitative study of federal governmental public health staff’s experiences working to develop co-funded multi-sectoral partnerships. Findings highlight the opportunities and challenges that emerge from government efforts to shift relations with traditional and novel partners in an effort to leverage partnerships for system change. Suggestions for how program implementers can take dynamic system attributes such as capacity, trust, and power relations into account when implementing multi-sectoral partnership programs are also offered. Finally, this dissertation concludes with a critical reflection on the research findings in light of the whole systems imperative and its implications for the public health response to obesity and NCDs.

Document type: 
Thesis
File(s): 
Supervisor(s): 
Diane Finegood
Department: 
Health Sciences: Faculty of Health Sciences
Thesis type: 
(Thesis) Ph.D.