Epidemiology & Biostatistics

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    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.
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    RACIAL AND ETHNIC DISPARITIES OF BREAST CANCER RISK: THE ROLE OF INDIVIDUAL AND NEIGHBORHOOD-LEVEL CARDIOMETABOLIC FACTORS
    (2023) Ogbenna, Bethany Townsend; Dallal, Cher; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: Observed racial and ethnic disparities in breast cancer are complex, in part, due to biological and behavioral factors at the individual and neighborhood level. Cardiometabolic factors such as the use of cholesterol-lowering drugs and engaging in healthy lifestyle behaviors may reduce breast cancer risk, however, the current understanding of these factors among diverse racial and ethnic populations remains limited. Moreover, at the neighborhood-level, the extent to which neighborhood socioeconomic status (nSES) influences inflammatory profiles among racially and ethnically diverse populations remains unclear. Using data from the Multiethnic Cohort Study (MEC), this dissertation investigates cholesterol-lowering drug use (Aim I) and a Healthy Lifestyle Index (HLI) (Aim II) in relation to postmenopausal breast cancer risk by race and ethnicity; and, assesses associations between nSES and inflammatory biomarkers among adults (Aim III). Methods: Prospective cohort analyses were conducted among postmenopausal women who completed the third MEC follow-up questionnaire in 2003 (Aim 1, n=41,394) or the baseline questionnaire in 1993-1996 (Aim 2, n=65,561) and were followed until 2017 for invasive breast cancer diagnoses (n=1,681 and 4,555 cases, respectively). Multivariable adjusted hazard ratios [HR] and 95% confidence intervals [95% CI] were estimated using Cox proportional hazards regression. For Aim III, multivariable linear regression assessed cross-sectional associations between nSES and inflammatory serum biomarkers (adiponectin, leptin and C-reactive protein) among adults residing in California (n=6,919) and Hawaii (n=6,899) (2000-2017). Results: Cholesterol-lowering drug use (Aim 1) and duration was not associated with breast cancer risk among all women with no statistically significant heterogeneity in associations by race and ethnicity (p-interaction >0.05). In Aim 2 analyses, women with a higher HLI score (Tertile (T)) had a reduced risk of breast cancer (HRT3 vs T1: 0.76; 95% CI: 0.69, 0.84; HRT2 vs T1: 0.88; 95% CI: 0.79, 0.97) compared to women in the lowest HLI tertile with a significant dose-response observed (p-trend <0.01). Similar patterns were observed across all racial and ethnic groups of women. In California and Hawaii, individuals living in low nSES neighborhoods had higher serum levels of CRP (p-trend <0.001; p-trend = 0.02, respectively) and leptin (p-trend <0.001) while adiponectin levels were lower (p-trend <0.01; p-trend = 0.03, respectively) compared to individuals living in neighborhoods with high nSES. Additional adjustment for body mass index attenuated these associations (p-trend >0.05) (Aim III). Public Health Impact: Findings from this dissertation further support engaging in healthy lifestyle behaviors as a preventative strategy for breast cancer reduction among multiethnic populations of postmenopausal women whereas cholesterol-lowering drug use was not associated with reductions in risk. In addition, residing in low nSES neighborhoods was associated with less favorable inflammatory biomarkers levels.
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    Intersectional stigma, self-efficacy, depression, and resilience: a Rasch analysis
    (2022) Reuben, Jacqueline; Liu, Hongjie; Turpin, Rodman; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: Black men who have sex with men (BMSM) are disproportionally affected by negative health outcomes associated with stigma related to both their racial and sexual minority status. Foundational to understanding stigma is the ability to correctly measure this latent construct. The Rasch model is a probabilistic model for analyzing categorical data that was developed to improve the measurement of latent traits. This study, grounded in intersectional minority stress theory, reviewed the application of Rasch analysis in the HIV/AIDS literature (Aim 1) and used the Rasch model to calibrate person measures to assess the interrelationships among internalized stigma, resilience, self-efficacy, and psychologic well-being among BMSM (Aims 2 and 3). Methods: For Aim 1, we conducted a systematic review of the literature following PRISMA guidelines. Aims 2 and 3 used data from a cross-sectional online survey of 151 HIV-negative BMSM in 2020. For Aim 2, we conducted Rasch analysis to assess the psychometric properties of the internalized racism (IR), internalized homophobia (IH), self-efficacy, and resilience scales. For Aim 3, we used linear regression and path analysis of the Rasch-calibrated person measures to examine the mediating and modifying effects of self-efficacy and resilience on the relationship between intersectional stigma and depressive symptoms. Results: For Aim 1, after screening 183 articles, 45 articles were included in the analysis. Strengths and weaknesses of using the Rasch approach were summarized. For Aim 2, the final IR scale had a person reliability and separation of 0.91 and 3.13, respectively, and an item reliability and separation of 0.94 and 4.01, respectively. The final IH scale had a person reliability and separation of 0.88 and 2.72, respectively, and an item reliability and separation of 0.79 and 1.95, respectively. For Aim 3, IR (β=0.296, 95% CI [0.133, 0.458]) and IH (β=0.414, 95% CI [0.204,0.623]) were independently and positively associated with depression in multivariable models controlling for age, income, and relationship status. Resilience and self-efficacy modified the relationship between IH and depression (βIHxRES=-0.034, 95% CI [-0.060, -0.008] and βIHxSE=-.056, 95% CI [-0.113, 0.00], respectively), but there was no evidence of effect modification by resilience or self-efficacy on the association between IR and depression. Public health implications: Our findings suggest that interventions targeting multiply marginalized groups such as BMSM that address co-occurring forms of stigma and foster positive self-evaluation and coping skills may reduce the negative consequences of internalized stigma on mental health outcomes.
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    The effects of HIV criminalization laws (and their enforcement) on HIV risk among Black and Hispanic populations
    (2022) Keralis, Jessica Maciel; Nguyen, Quynh C; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: In the U.S., 25 states have laws that explicitly criminalize the transmission or exposure of HIV. This study, grounded in Nancy Krieger's ecosocial theory, estimated the association between HIV criminalization laws and state- (Aim 1) and county-level (Aim 2) HIV incidence rates, as well as individual HIV testing history (Aim 3), and assessed effect modification by overpolicing, using incarceration rates as a proxy. Methods: The study uses data from state- and county-level HIV incidence data from AIDSVu (2010-2019), incarceration data from the Vera Institute of Justice (2010-2018), and HIV testing data from BRFSS (2016-2019). For Aim 1, a longitudinal analysis was conducted using multivariate marginal Poisson GEE models to estimate rate ratios. For Aim 2, count-rate hierarchical (multilevel) models were fitted to estimate rate ratios. For Aim 3, logistic regression models were fitted to estimate odds ratios. Results: The presence of a state HIV testing law was associated with a higher state HIV incidence in the general and Hispanic populations (aRR=1.48 and 1.68, respectively), but higher incarceration at the state level did not significantly modify the relationship between the law and HIV incidence. At the county level, being in a state with an HIV-specific criminalization statute was associated with a higher county-wide HIV incidence rate for all three populations (aRR=1.14, 1.30, and 1.32 for the general, Black, and Hispanic populations, respectively). Unlike the state-level analysis, this association was attenuated by a higher jailed population rate for the general and Black populations. The effect modification was statistically significant for the general population (p=0.01) and marginally significant for the Black population (p=0.06). Finally, the presence of a state HIV testing law (aOR=1.06) was associated with a greater likelihood of HIV testing history in the general population. However, in HIV criminalization states, heavier policing negatively modified the effect of the law on the likelihood of having ever received an HIV test (p<0.01). Public health implications: This study contributes to a gap in the literature by using recent data to estimate the association of HIV criminalization laws and their enforcement with HIV incidence rates and HIV testing behavior.
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    Metformin and statins in relation to ovarian cancer: implications for risk and potential etiologic pathways
    (2022) Irvin, Sarah Renee; Dallal, Cher; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: Metabolic factors, including obesity, diabetes, and circulating lipids are associated with increased risk of ovarian cancer, the most fatal gynecologic malignancy. Drugs targeting these conditions have drawn interest as potential chemopreventive agents, but limited studies have examined relationships with ovarian cancer overall, by possible benefit groups or with regards to related etiologic pathways. This dissertation examined medications that target metabolic abnormalities with risk of ovarian cancer, and expression of a pro-tumorigenic lipid pathway in ovarian cancer tissue.Methods: Nested case-control studies of metformin (Aim 1) and statin (Aim 2) use in relation to ovarian cancer (cases n=9,207 and 10:1 frequency-matched controls n=92,070) were conducted in Clinical Practice Research Datalink (CPRD) (1987-2020), a primary care database in the United Kingdom. Aim 3 was a case-only analysis from The Polish Ovarian Cancer Study (POCS) (2001-2003, n=166) determining expression of sphingosine-1-phosphate receptors S1PR1 and S1PR3 in ovarian cancer tissue. Multivariable logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CI) for associations between medication use and ovarian cancer in CPRD (Aims 1 and 2), and cancer characteristics with marker expression in POCS (Aim 3). Results: Within the CPRD analyses, metabolic conditions such as obesity (OR 1.19, 95% CI 1.11-1.28) and polycystic ovarian syndrome (OR 1.66, 95% CI 1.17-2.35) were significantly associated with increased ovarian cancer risk. However, neither metformin (OR 1.01, 95% CI 0.91-1.13) nor statin use (OR 1.02, 95% CI 0.96-1.08) was associated with ovarian cancer risk. Associations did not differ by drug indications (pint >0.05), individual statin or class. In Aim 3, strong expression of lipid markers in ovarian cancer tissue significantly differed by histotype (p<0.01). Lower marker expression was observed in non-serous tumors compared to serous, but expression was not associated with cancer risk factors or survival. Conclusion: Findings from this dissertation do not support use of metformin or statins as chemopreventive agents. However, as most CPRD users had an indication, it remains unclear whether findings are generalizable to the at-risk population for ovarian cancer. Strong expression of lipid markers in ovarian cancer tissue suggests involvement in carcinogenesis; additional molecular studies are needed to elucidate their role.
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    Self-reported discrimination among Asian Americans: An examination of its measurement and relationship with health-related quality of life
    (2019) Jung, Mary; Lee, Sunmin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Labeled as a “model minority,” Asian Americans have often been excluded from the dialogue on discrimination. Previous studies frequently used discrimination measures that were initially developed for African Americans and lack items related to language and nativity. Although discrimination adversely affects mental and physical health, its relationship to health-related quality of life (HRQOL) has been understudied in this population. This dissertation evaluated self-reported discrimination among Asian Americans by examining its measurement and relationship with HRQOL. Manuscript 1 assessed the psychometric properties of everyday (ERDS) and major racial discrimination scales (MRDS) that were developed for Asian Americans. In a sample of 569 Asian American immigrant adults, reliability was excellent for ERDS but moderate for MRDS (Cronbach’s α=0.94 and 0.60). The latter is likely low given that MRDS is an inventory of events. For construct validity, weak positive linear correlations with perceived stress and depressive symptoms were observed (r=0.22 and 0.28 for ERDS and r=0.11 and 0.14 for MRDS; p<0.001). Factor analysis confirmed the unidimensionality of both measures. Manuscript 2 cross-sectionally examined the association between the racial discrimination measures from Manuscript 1 and HRQOL among 524 foreign-born Asian American adults. Multivariable logistic regression and negative binomial regression were performed to examine self-rated health (poor vs. good) and days of poor physical health, mental health, and activity limitation. ERDS (IRR range: 1.04-1.08) and MRDS scores (IRR range: 1.19-1.61) were significantly and positively associated with worse HRQOL for all measures, except for self-rated health. Manuscript 3 examined discrimination trajectories and assessed their relationship with self-rated health in a longitudinal, multi-ethnic sample of 2,004 middle-aged women in the Study of Women’s Health Across the Nation (SWAN). Group-based trajectory analysis identified three distinct discrimination groups. The “high and decreasing” but not “moderate and decreasing” group was significantly associated with poor self-rated health compared to the “low and decreasing” group (OR=1.61; 95% CI: 1.12-2.31). This dissertation provides insight into discrimination measures and their relationships with HRQOL among Asian Americans. Proper measurement and health impact assessment of discrimination in this population can contribute to better monitoring and provide improved accountability and support for interventions and public policies.
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    ESTIMATING RISK OF AIRBORNE INFLUENZA TRANSMISSION IN A CONTROLLED ENVIRONMENT
    (2019) Bueno de Mesquita, Paul Jacob; Milton, Donald K.; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Pandemic preparedness is weakened by uncertainty about the relative importance of influenza transmission modes, particularly airborne droplet nuclei (aerosols). A human-challenge transmission trial in a controlled environment was conducted to address this uncertainty. Healthy, seronegative volunteer ‘Donors’ (N=52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2) and exposed to seronegative ‘Recipients’ randomized to intervention (N=40) or control (N=35) groups. Intervention recipients wore face shields and hand sanitized frequently to limit large droplet and contact transmission. A transmitted infection, confirmed by serology in a control recipient, yielded a 1.3% SAR overall. This was significantly less than the expected 16% SAR (p <0.001) based on a proof-of-concept study that used half as many Donors and exposure days. The main difference between these studies was mechanical building ventilation in the follow-on study, suggesting a possible role for aerosols. The extent to which Donor viral shedding was similar to that of mild, natural infections and may be useful for studying transmission was investigated. The only available aerosol shedding comparison data comes from a population of adults with influenza A H3 infection enrolled on the basis of febrile illness plus cough or sore throat, or positive Quidel QuickVue rapid test (N=83). Systematic differences in case selection compared with Donors yielded more severe cases and introduced bias. To account for differences in illness severity, propensity score matching, stratification, and inverse weighting ultimately demonstrated that the experimental and naturally infected groups were too different to compare without bias. While acknowledging the uncertainty in the generalizability of the current challenge model, observed aerosol shedding and CO2 were used in the rebreathed-air version of the Wells-Riley equation to compute average quantum generation rates (95% CI) 0.029 (0.027, 0.03) and 0.11 (0.088, 0.12) per hour for infected Donors and fine aerosol shedding Donors, respectively. Donors shed 1.4E+5 (1.0E+5, 1.8E+5) airborne viral RNA copies per quantum (ID63). This dissertation provides evidence for airborne transmission, presents a methodology for estimating an airborne dose, and suggests a role for building ventilation in reducing risk and the need for future observational studies to evaluate transmission modes in non-experimental settings with greater generalizability.
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    THE ASSOCIATION BETWEEN SUBMICROSCOPIC MALARIA INFECTION AND FEVER: FINDINGS FROM A CROSS-SECTIONAL STUDY IN MALAWI
    (2019) Barrall, Angelica Lynne; Dyer, Typhanye V; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Individuals with submicroscopic malaria infection are an important reservoir for transmission, but the clinical consequences of these low-density parasitemia infections are poorly understood. Using cross-sectional data from six household-based surveys conducted during the dry and rainy seasons in Malawi from 2012 to 2014, this study examined the association between submicroscopic infection and fever in children and adults. For each survey, 900 households were recruited from three distinct ecological settings in southern Malawi to participate in the study (N=22,145). Overall prevalence of submicroscopic infection in the analytic sample was 8.1%. In a generalized linear mixed model accounting for clustering at the household and neighborhood levels and controlling for age and survey number, submicroscopic infection predicted fever in the dry season only (OR=1.66; 95% CI: 1.04, 2.66). Therefore, fever might not be a consistent marker of submicroscopic infection, but identification and treatment of low parasitemia infections is necessary to eliminate malaria transmission.
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    Using the Index of Concentration at the Extremes to Examine the Impact of Air Pollution Exposure on Infant Mortality in the United States
    (2019) Ammons, Samantha; Nguyen, Quynh; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: The concentration of privilege in a geographic area can determine how vital resources are distributed among certain groups in that area, thus influencing a community’s health. High air pollutant exposure is often concentrated in deprived neighborhoods with lack of vital resources. Objective: Determine whether states with a high concentration of air pollution exposure have higher infant mortality rates (IMR) than states with lower concentrations of air pollution exposure. Methods: The Index of Concentration of the Extreme was utilized to measure the concentration of air pollution exposure for each state. Incidence Rate Ratios and 95% Confidence Intervals for state infant mortality rate were computed using Poisson regression in Statistical Analysis Software. Results: States with high concentrations of air pollution exposure had 19% lower IMR than states with low air pollution exposure (95%CI:0.70 – 0.94). Conclusions: These findings can enable researchers to conduct census-tract research on adverse health outcomes and societal distributions.
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    THE IMPACT OF SOCIOECONOMIC STATUS ON SERIOUS MENTAL ILLNESS AND CARDIOVASCULAR DISEASE AMONG AFRICAN AMERICANS
    (2017) Wilkerson, Thomas G.; Dyer, Typhanye; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Cardiovascular disease (CVD) tends to be more prevalent in individuals older than 18 years of age with serious mental illness (SMI) and CVD is the leading cause of death of African Americans in the United States. Socioeconomic status (SES) is a major confounder that distorts the association of SMI with CVD in the African American population. The goal of this study is to measure the relationship between SMI and CVD in middle and upper income level African Americans. To accomplish this goal the three specific aims are as follows: Aim 1: To measure the prevalence of CVD in the study population. Aim 2: To measure the prevalence of SMI in the study population. Aim 3: To measure the strength of the association between SMI and CVD in the study population. The study is a cross-sectional study using secondary data analysis from four merged 2015 National Health Interview Survey (NHIS) datasets.