Theses and Dissertations from UMD
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Item EXPLORING ENVIRONMENTAL INJUSTICE AND AIR POLLUTION-RELATED HEALTH EFFECTS IN PRINCE GEORGE'S COUNTY, MARYLAND(2024) Ravichandran, Vivek; Wilson, Sacoby M; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polluting facilities have been historically sited in disadvantaged communities of color, known as environmental justice (EJ) communities, due to limited perceived community resistance and mobilization. There is a plethora of air quality disparity research but a gap persists in ascertaining the health inequities associated with community exposure to air pollutants, such as particulate matter (PM) and black carbon (BC), at the neighborhood resolution. To address this gap in EJ science, this dissertation has four specific aims: (1) Implement the community-based participatory research (CBPR) framework to expand and enhance the community-engaged infrastructure to ensure the success of Aims 2-4; (2) Identify spatiotemporal pollution patterns across the Route 50-Sheriff Road-Kenilworth Ave Quadrant; (3) Determine short-term health impacts associated with community exposure to PM and BC via a panel study involving pulse oximeters to correlate elevated PM and BC levels to blood oxygen saturation (SpO2 levels); and (4) Conduct semi-structured interviews and use NVivo to perform thematic analysis on barriers and motivating factors towards passing EJ legislation. My findings demonstrated that a more diverse and representative community advisory board (CAB) allowed us to successfully conduct research while maintaining trust within the community, and bringing in voices from various demographic groups, including different ethnicities, ages, income levels, and geographic locations. This led to a more comprehensive understanding of the community's concerns, priorities, and needs related to air quality. Additionally, my findings revealed that both PM and BC levels were elevated during morning rush periods. PM levels did not exceed the Environmental Protection Agency (EPA) annual standards, but did exceed the more protective World Health Organization (WHO) guidelines. Robert Gray Elementary School exhibited higher PM levels than the other Quadrant sites. Furthermore, BC levels at Fairmount Heights High School were above the threshold defined in the literature above which cognitive inhibition and poor respiratory outcomes have been observed, highlighting the effect of air pollution exposure on vulnerable life stages in the Quadrant. BC peaks were also observed 10-15x these unofficial health-based thresholds. Using a pulse oximetry panel study, we found previous and concurrent day lagged fine particulate matter (PM2.5) was weakly associated with reductions in SpO2. Using NVivo, we identified 18 parent codes and 27 subcategories from our semi-structured interviews with Maryland policymakers/agency staff. Key barriers were: (1) the lack of strategic EJ plans; (2) limited community engagement particularly from those living in communities impacted by environmental injustice; and (3) interagency and policymaker collaboration exacerbated by a clear partisan divide. These findings provide evidence of previous misclassified exposure assessments from sparse existing regulatory monitors, present strategies for overcoming EJ barriers in the state, and underscore the importance of collaboration, community engagement, and policy reform to address environmental disparities and promote environmental justice.Item CLIMATE CHANGE RELATED EXTREME EVENTS AND ADVERSE HEALTH OUTCOMES AMONG HEMODIALYSIS PATIENTS(2024) Song, Hyeonjin; Sapkota, Amir AS; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The increased frequency and intensity of extreme heat events (EHEs) and wildfires due to climate change are posing significant threats to vulnerable communicates including end-stage kidney disease (ESKD) patients. The specific aims of this dissertation are to Aim 1) Examine the association between EHEs exposure and serum concentrations of sodium and potassium among hemodialysis patients in the Western U.S. (2008-2018), Aim 2) Quantify the mortality and hospitalization risk associated with exposure to 2023 Canadian wildfire-related air pollution in the Eastern U.S., and Aim 3) Investigate how EHEs modify the association between wildfire-related air pollution exposure and the risk of mortality and hospitalization among hemodialysis patients in the Western U.S. (2010-2018). We analyzed health records of patients who receiving hemodialysis treatment at Fresenius Kidney Care clinics. We used the 10°C increase in daily average temperature and daily extreme heat events (EHEs) of each county as the primary exposures. The presence of wildfire smoke plume and wildfire fine particulate matter (PM2.5) concentrations for each clinic were measured using satellite-derived smoke polygons (Hazard Mapping System) and ground-based PM2.5 monitors (Air Quality System). We estimated mean serum sodium and potassium change per 10 °C increase in daily average ambient temperature using random intercepts linear mixed-effects models. We employed a time-stratified case-crossover analysis with conditional quasi-Poisson model to investigate the risks of mortality and hospitalization associated with exposure to wildfire-related air pollution and EHEs. In the first study, a 10°C increase in daily average temperature was associated with 0.43 mEq/L (95% Confidence Interval [CI]: 0.47, 0.59) increase in serum sodium during July-August. The serum sodium was 0.15 mEq/L (95% CI: 0.10, 0.20) higher during EHE days compared to non-EHE days. The serum potassium level did not show a significant change. In the second study, during June-July 2023, the presence of wildfire smoke plume was associated with an 18% increase in all-cause mortality risk (Rate Ratio [RR]:1.18; 95% CI: 1.13, 1.24) and a 3% increase in all-cause hospitalization risk (RR:1.03; 95% CI: 1.00, 1.07). A 10-μg/m3 increase in wildfire-related PM2.5 was associated with a 139% increase in all-cause mortality (RR: 2.39; 95% CI: 1.79, 3.18) and a 33% increase in all-cause hospitalization (RR:1.33; 95% CI: 1.10, 1.62). In the third study, we observed significant interactions between EHEs and wildfire smoke plume for mortality RRs among the hemodialysis patients in the Western U.S. Mortality risk was considerably higher when hemodialysis patients were simultaneously exposed to wildfire smoke plume and EHE compared to wildfire smoke plume alone (RR: 1.52; 95% CI: 1.25, 1.86 vs. RR: 1.15; 95% CI: 1.08, 1.23). We did not observe a significant interaction for all-cause hospitalization. Our findings underscore the need to revise operational and care protocols to prepare for such potential join exposures to extreme events that are exacerbated by ongoing climate change. Future work should focus on developing early warning systems to enhance resilience against such threats.Item Second Wave Mechanics(2024) Fabbri, Anthony; Herrmann, Jeffrey W; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The COVID-19 pandemic experienced very well-documented "waves" of the virus's progression, which can be analyzed to predict future wave behavior. This thesis describes a data analysis algorithm for analyzing pandemic behavior and other, similar problems. This involves splitting the linear and sinusoidal elements of a pandemic in order to predict the behavior of future "waves" of infection from previous "waves" of infection, creating a very long-term prediction of a pandemic. Common wave shape patterns can also be identified, to predict the pattern of mutations that have recently occurred, but have not become popularly known as yet, to predict the remaining future outcome of the wave. By only considering the patterns in the data that could possibly have acted in tandem to generate the observed results, many false patterns can be eliminated, and, therefore, hidden variables can be estimated to a very high degree of probability. Similar mathematical relationships can reveal hidden variables in other underlying differential equations.Item COVID-19 Vaccine Hesitancy and Uptake in the United States Considered Through the Lens of Health Behavior Theory(2024) Kauffman, Lauren Emily; Nguyen, Quynh; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Given the low COVID-19 vaccine uptake rates in many areas of the United States despite their demonstrated safety and effectiveness, COVID-19 vaccine hesitancy and vaccination barriers continue to be critical areas of research in epidemiology and behavioral health science. This series of studies focuses on COVID-19 vaccine hesitancy and vaccination barriers, as they relate to vaccination intention and vaccine uptake, considered in the context of established health behavior theories. The first study is a systematic review of existing research on COVID-19 vaccine hesitancy using one or more health behavior theories as key components of the design or analysis. This study examined the types of theories that are most often used, how they are used, and where research gaps exist. The remaining two studies use data from the U.S. COVID-19 Trends and Impact Survey, a national cross-sectional survey. The second study investigates the association between recent feelings of anxiety or depression and vaccination intention, as well as between these feelings and identifying with specific vaccine hesitancy reasons. The third study examines vaccine hesitancy and barriers among those with chronic illness or disease, a particularly vulnerable population. Factor analysis was conducted using constructs from the Theory of Planned Behavior as a framework, and the results were used in a regression model to investigate the association between these underlying factors and vaccination intention. This research demonstrated the usefulness of the Theory of Planned Behavior, the Health Belief Model, and the 3 Cs Model in existing and future COVID-19 vaccine hesitancy research, as well as identified Protection Motivation Theory as a promising area for future research. Additionally, psychological states were demonstrated to be significantly associated with vaccine hesitancy, adjusting for demographic, socioeconomic, and time factors. Lastly, the Theory of Planned Behavior was found to be applicable to those unvaccinated and with chronic illness, as the construct factor scores developed were significantly associated with vaccine hesitancy (adjusting for the presence of specific chronic conditions and demographic, socioeconomic, and time factors). These associations were also consistently demonstrated in subgroup analyses of participants with specific chronic conditions.Item EVALUATING THE EFFECTS OF MODIFIABLE LIFESTYLE AND CARDIOVASCULAR HEALTH FACTORS ON DIABETES LIFE EXPECTANCY IN NHANES AND BRAIN AGING IN UK BIOBANK(2024) Feng, Li; Lei, David K.Y. DL; Ma, Tianzhou TM; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation explored the impact of lifestyle and cardiovascular health factors on aging, particularly focusing on individuals with diabetes, the effects of blood pressure on brain aging, and the influence of cardiovascular health and genetic predispositions on brain white matter aging.The first study examined the trends in lifestyle quality among US adults with type 2 diabetes from 1999 to 2018 using NHANES data, involving 7,410 participants. A healthy lifestyle score encompassing smoking, drinking, physical activity, and diet showed a slight increased over the years. Notably, disparities remained significant by socioeconomic groups. The study found that adherence to low-risk lifestyle factors was associated with a 55%-57% lower risk of all-cause mortality, emphasizing the importance of lifestyle modification in diabetes management, and it was independent of cardiovascular risk control. The second study investigated the causal effect of elevated blood pressure on white matter brain aging in a cohort of 228,473 European ancestries aged 40-69 from the UK Biobank by using two-sample Mendelian randomization. Our result revealed that high blood pressure, particularly diastolic, accelerated the machine-learning-derived white matter brain age gap, based on white matter microstructure integrity measured by fractional anisotropy derived from diffusion tensor imaging data, with a causal effect evidence found in late middle-aged women. This underscores the importance of blood pressure control in preventing brain aging, especially in post-menopausal women. Lastly, the impact of Life's Essential 8 (LE8), a comprehensive measure of cardiovascular health (lifestyle part: diet, smoke, physical activity, sleep; health part: BMI, blood sugar, blood pressure, blood lipid), on white matter brain aging was assessed, with a particular focus on how the APOE4 genotype modifies the relationship. Analyzing data from 18,817 European ancestries aged 40-60 from the UK Biobank, the study revealed that higher LE8 scores correlated with a younger brain age. Interestingly, the effect varied significantly with APOE4 status, highlighting the need for personalized health strategies based on genetic profiles. In conclusion, these studies collectively highlight the crucial role of modifiable lifestyle and health factors in managing chronic diseases, controlling blood pressure, and maintaining brain health, with an emphasis on the integration of genetic profiles for personalized healthcare.Item Social Determinants of Cardiovascular Disease Across the Life Course(2023) Ng, Amanda Erin; Dyer, Typhanye; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)According to data from the National Center for Health Statistics, cardiovascular disease is one of the leading causes of death in the United States, contributing to about 697,000 (or 1 in 5) deaths in 2020 alone. Given the public health burden of this disease, it is imperative that research identifies and continues to investigate population factors that may contribute to or alleviate this burden in the United States. The proposed study aimed to analyze such factors across the life course. Study 1 examined associations between an expanded set of Adverse Childhood Experiences (ACEs) and childhood obesity among 10-17 year olds using the National Survey of Children’s Health, as well as sex and age differences within these associations. Study 2 investigated high optimism as a modifier and mediator of the association between childhood socioeconomic disadvantage and CVD in midlife, using the Midlife in the United States Study, a U.S. prospective cohort. Study 3 examined temporal trends in the associations between adult socioeconomic status and CVD mortality using nationally-representative data from the 1997-2018 National Health Interview Survey.Item Development of a Multilocus Sequence Typing Scheme for Avibacterium paragallinarum(2023) Harris, Alyssa Meihua; Ghanem, Mostafa; Veterinary Medical Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Avibacterium paragallinarum (A. paragallinarum), the causative agent of the respiratory disease Infectious Coryza (IC) in chickens, has seen a rising incidence in the United States. Current strain differentiation is inadequate for detailed epidemiological analysis. The objective of this study was to develop a Multilocus sequence typing (MLST) scheme for A. paragallinarum for outbreak investigations and to offer a better tool for strain differentiation. By evaluating whole genome sequences and clinical samples, we designed PCR amplicons for eighteen gene segments, selected six genes for their nucleotide diversity and discrimination potential. The MLST was used to differentiate seventy-five samples. Our MLST showed greater discriminatory power than existing HPG2-based methods, aligning closely with adhoc core genome MLST in 75 tested sample. Our newly developed MLST scheme enables more accurate strain differentiation, allowing for better understanding of A. paragallinarum epidemiology and population structure to help prevention and control efforts worldwide.Item EXHALED BREATH AEROSOL TRANSMISSION OF ACUTE RESPIRATORY INFECTIONS(2023) Lai, Jianyu; Milton, Donald K; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Acute respiratory infections (ARIs), which usually appear in the form of common colds and influenza, as well as outbreak brought on by emerging viruses such as SARS-CoV-2, result in millions of deaths and hospitalizations each year. Aerosols being exhaled by infected population and inhaled by susceptible population has been identified as an important transmission route for ARIs; yet few studies have compared the viral load in exhaled breath aerosol (EBA) in naturally and experimentally infected cases, as well as among various infections. The specific aims of this dissertation were: 1) examine the comparability of EBA viral shedding between experimentally and a full range of natural ambulatory influenza cases; 2) compare seasonal coronavirus, influenza, SARS-CoV-2 Omicron, and other SARS-CoV-2 variants in terms of viral loads in exhaled breath aerosols; and 3) examine the relative efficacy of face masks, KN95, and N95 respirators as source control for SARS-CoV-2. We analyzed data from four studies that collected 30-minute fine (≤5 μm) and coarse (>5 μm) EBA samples using a Gesundheit-II sampler. Viral RNA load in EBA was quantified using real-time RT-PCR. Nasal inoculation of influenza virus A/Wisconsin/67/2005 showed lower EBA viral shedding compared to the natural influenza A H3 infections. Among the viruses studied, SARS-CoV-2 Omicron variants demonstrated the highest viral RNA loads in both EBA size fractions, emphasizing its superior spread capability via inhalation. Furthermore, while all masks and respirators showed significant reductions in viral RNA load in exhaled aerosols, the duckbill N95 respirators stood out, providing reductions of up to 99% and outperforming both surgical and cloth masks, and KN95 respirators. Given the evident transmission risk via inhalation for the studied viruses, measures such as masking and indoor air hygiene are crucial. The pronounced efficacy of N95 respirators highlights their importance in healthcare settings and places with vulnerable populations, especially during periods of heightened respiratory viral infections.Item EPIDEMIOLOGICAL TRANSITION AND SHIFTING MORTALITY INEQUALITY: AN EXTENSION OF FUNDAMENTAL CAUSE THEORY(2023) Ruan, Hangqing; Kahn, Joan JK; Sociology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The dissertation addresses two "public health puzzles" in US mortality inequality trends: (1) SES inequalities in mortality have been growing wider despite declines in overall mortality levels and the expansion of social welfare policies; (2) mortality inequalities present diverging trends across age groups, with declines at younger ages but growth at older ages. These puzzles challenge existing theories in explaining the complex dynamics of mortality disparities. The study aims to bridge this gap by proposing an alternative theoretical framework that combines Fundamental Cause Theory with the concept of epidemiological transition.Previous research has focused primarily on socioeconomic factors as the main drivers of widening mortality disparities. However, this dissertation argues that mortality inequalities can evolve independently of socioeconomic factors due to shifts in disease patterns towards non-communicable diseases and advancements in health-beneficial innovations. By analyzing county-level US mortality rates from 1968 to 2020, this study reveals that mortality inequality related to infectious diseases declined in the early 1970s and remained stable over time. On the other hand, mortality inequality related to non-communicable diseases remained at a low level during the 1970s but saw a significant increase since the 1980s. Further, this study found that mortality inequality from non-communicable diseases is more pronounced in middle-aged and older adults, and the age distribution of mortality inequality progressively shifts towards older ages. This study contributes to the existing literature with a new theoretical perspective to understand the developments of mortality inequalities over time. This framework sheds light on the two "public health puzzles” and emphasizes the crucial role of disease patterns prevailing during specific historical periods in understanding the developments of mortality inequality. Furthermore, the study underlines the interplay of disease patterns, prevention/treatment innovations, and social and economic inequalities in collectively shaping the future of mortality and health disparities. It also sheds light on the social-political circumstances of medical innovation as well as behavioral factors over the life course in determining future population health and health inequalities.Item EXAMINING THE IMPACT OF PRECONCEPTION AND EARLY PREGNANCY SERUM LEVELS OF MATERNAL VITAMIN D ON CLINICAL MARKERS OF IMPLANTATION AND PREECLAMPSIA(2023) Alkhalaf, Zeina; Thoma, Marie; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Vitamin D is a hormone rather than a vitamin, that is essential for overall health and wellbeing, including but not limited to the reproductive system. Although vitamin D is available through several sources, such as natural ultraviolet sunlight, food, and supplements, low circulating 25-hydroxyvitamin D (25(OH)D) levels of <30 ng/mL are common among pregnant women, with up to 69% of the US population suffering from the condition. Epidemiologic studies have suggested that low maternal serum 25(OH)D levels may be associated with adverse pregnancy outcomes, such as early pregnancy loss and preeclampsia, which may be initiated early in the pregnancy process during implantation and placentation. From a life course perspective, the periconception and early pregnancy period marks a critical time for establishing a healthy pregnancy. Implantation and placentation occur early in pregnancy and involve a complex process that relies on optimal endometrial receptivity and a host of hormonal and immunologic signaling events. Disruptions to this process may be indicated by early clinical markers of pregnancy complications (e.g., vaginal bleeding or subchorionic hemorrhage) and associated with later adverse outcomes (e.g., preeclampsia). In contrast, higher Human Chorionic Gonadotropin (hCG) levels, which have been linked to nausea and vomiting, may be markers of robust implantation and placentation. Therefore, I sought to investigate the preconception and early gestation maternal serum 25(OH)D levels on: (i) vaginal bleeding and subchorionic hemorrhage; (ii) nausea and vomiting; (iii) preeclampsia. In Aim 1, an analysis of medical record documentation of vaginal bleeding and subchorionic hemorrhage found that women who were persistently deficient/insufficient in maternal serum 25(OH)D at both preconception and 8-week gestation had 2.18 times higher (95% CI: 1.13, 4.20) odds of having subchorionic hemorrhage compared to women who remained sufficient across both time periods, even after adjustment for potential confounders. Additionally, an analysis of daily diaries showed women with deficient 25(OH)D levels had a higher odds (OR: 3.02, 95% CI: 1.13, 8.13) of moderate/heavy bleeding versus none compared to women with sufficient 25(OH)D levels based on self-reported daily diaries on vaginal bleeding at the start of pregnancy. In Aim 2, women with persistently deficient 25(OH)D levels at both preconception and early gestation had lower odds (OR: 0.34, 95% CI: 0.20, 0.60) of experiencing nausea and vomiting based on medical records. In comparison, women who increased their 25(OH)D levels early in pregnancy (i.e., were deficient/insufficient at preconception then became sufficient at 8-week gestation) had 1.71 (95% CI: 1.12, 2.61) times higher odds of nausea and vomiting compared to those who were persistently sufficient across both time periods. Based on self-reported nausea and vomiting symptoms from daily diaries, deficient 25(O)D was associated with lower odds (OR 0.65; 95% CI 0.40, 1.06) of both nausea and vomiting when comparing to sufficient 25(OH)D levels. In Aim 3, women who had deficient 25(OH)D at preconception had an increased risk (RR: 1.45, 95% CI: 0.64, 3.29) of preeclampsia (as identified from medical records), although results were insignificant. Linear spline models demonstrated that the risk of preeclampsia declined with each 1 ng/mL increase of 25(OH)D levels up to 40-45 ng/mL (RR: 0.97, 95% CI: (0.93, 1.00), but that levels beyond this threshold show an increase in the risk of preeclampsia for each 1 ng/mL increase in 25(OH)D (RR: 1.03; 95% CI: 1.00, 1.06). This research highlights the importance of exploring the maternal serum levels of 25(OH)D at both preconception and early gestation and how it may affect adverse pregnancy outcomes, such as vaginal bleeding, subchorionic hemorrhage, preeclampsia, and pregnancy outcomes that signify a robust implantation response, such as nausea and or vomiting. It further underscores the importance of assessing maternal serum 25(OH)D levels prior to critical time of implantation and placentation and potential biologic mechanisms that may lead to adverse pregnancy outcomes. Supporting healthy implantation and placentation is of utmost importance as this may guide the remainder of the health of the pregnancy, and any disruption to this process may increase the mother and infant’s risk of maternal morbidity and mortality (e.g., preeclampsia, vaginal bleeding, subchorionic hemorrhage). Future studies are needed with more diverse, larger sample sizes, and both paternal and maternal nutrition to further assess preconception nutritional risk factors on adverse and robust pregnancy outcomes. Accordingly, this research is vital as it may aid in identifying early factors that may reduce adverse maternal and infant health outcomes.