Epidemiology & Biostatistics

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End date: 2019Subject: search.filters.subject.Public health

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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.
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    The Health Implications of Stress among Asian Americans in the US and Chinese In China: the Effects of Perceived Stress and Caregiving Stress on Cardiovascular Risk Factors
    (2018) Lu, Xiaoxiao; Lee, Sunmin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Prior research suggests that stress plays a role in the etiology and progression of cardiovascular disease (CVD). To lend a more accurate depiction of the associations between stress and CVD risk factors, this dissertation used a comprehensive approach to conceptualizing stress by assessing two dimensions of stress: perceived stress and caregiving stress. The objective of this dissertation was to investigate the associations between multiple dimensions of stress and the risk factors of CVD. This dissertation also explored the potential mechanisms that underlie the relationships between stress and CVD risk factors. In Paper 1 (Chapter 3), we assessed the associations between perceived stress and hypertension across varying levels of social support and social network among 530 Chinese, Korean and Vietnamese Americans. Results indicated that individuals with high perceived stress were 61% more likely to have hypertension compared to those with low levels of perceived stress (Odds Ratio (OR): 1.61, 95% Confidence interval (CI): 1.15, 2.46). Social support had a direct beneficial effect on hypertension, irrespective of whether individuals were under stress. In Paper 2 (Chapter 4), we used five waves of longitudinal data from the China Health and Nutrition Survey to examine the association between parental caregiving and blood pressure among 2,586 Chinese women. We found that parental caregivers were associated with higher systolic (β-coefficient (β) = 1.16; p ≤ 0.01) and diastolic blood pressure (β = 0.75; p ≤ 0.01) compared with non-caregivers across multiple waves. In Paper 3 (Chapter 5), we investigated the relationship between caregiving trajectory and Metabolic Syndrome (MetS) among 1,636 Chinese women. Three caregiving trajectories were identified by using group-based trajectory analysis. Results showed that ‘rising to high-intense’ caregivers (OR = 1.90; 95% CI: 0.90, 4.00) and ‘stable low-intense’ caregivers (OR = 1.56; 95% CI: 1.06, 2.29) were associated with higher risk of MetS compared with non-caregivers. This dissertation is innovative in its examining the associations of multiple dimensions of stress with CVD risk factors among Asian subgroups. Findings from the proposed study will be used to develop future stress management interventions, and incorporating culturally and linguistically appropriate strategies into community outreach and education to decrease cardiovascular disease risk within the Asian population.
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    ASSOCIATIONS BETWEEN AMBIENT PARTICULATE MATTER EXPOSURES, STROKE, AND MARKERS OF CARDIOVASCULAR INFLAMMATION
    (2017) Fisher, Jared A.; Puett, Robin C; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Stroke is a leading cause of morbidity and mortality in the United States with 795,000 people experiencing a new or recurrent stroke every year. Identifying modifiable risk factors for stroke should therefore be considered a research priority. While associations between ambient exposure to air pollution and other cardiovascular diseases are well established in the literature, the evidence linking particulate matter (PM) air pollution exposures to the risk of ischemic or hemorrhagic stroke remains equivocal. Furthermore, the exact pathophysiologic mechanisms by which exposure to PM may lead to cerebrovascular events are not yet fully understood. Hypothesized pathways include the mediation of effects through a combination of inflammatory responses, autonomic dysregulation, and/or vascular endothelial disturbances. This dissertation addresses existing gaps in the literature in three separate studies. Two time-stratified case-crossover studies examined the association between short-term PM exposures and stroke risk, one in the Health Professionals Follow-up Study (HPFS) and the other among a large database of Maryland stroke hospitalizations. Conditional logistic regression models were used to examine associations by stroke subtype, population subgroups, and clinically-relevant variables. Our third study took place within the Nurses’ Health Study cohort. Multivariable linear regression models were used to examine the associations between PM and residential distance to road exposures and four inflammatory biomarkers (CRP, IL-6, fibrinogen, and ICAM-1). We found positive significant associations between PM10 and ischemic stroke events in the HPFS cohort, and associations were elevated for nonsmokers, aspirin nonusers, and those without a history of high cholesterol. Concentrations were elevated for both CRP and IL-6 among participants who lived close to a major roadway, but no significant results were found by estimated PM exposure. This work provides additional evidence that PM exposure is associated with ischemic stroke and adds to the current literature that those not currently taking aspirin and those without a history of high cholesterol may be at elevated risk. Although the direct role of inflammatory processes requires more investigation, this work does provide additional evidence that proximity to traffic may influence cardiovascular-related inflammation.
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    STAYING HEALTHY AFTER CANCER: THE HIDDEN INFLUENCE OF SOCIAL NETWORKS
    (2017) Guida, Jennifer Lyn; Liu, Hongjie; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Background: Few rigorous empirical studies have used social network models to investigate changes to the relationships most important to cancer survivors and their effects on health. The objective of this dissertation was to longitudinally examine the associations between egocentric social network change over time and physical, physiological, and mental health among cancer survivors and older adults without a history of cancer. Method: The National Social Life Health and Aging Project (NSHAP) (2004-2011) is a nationally representative cohort of older adults aged 57 and older. Physical functioning was measured with the Activities of Daily Living Scale and inflammation was measured by C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), and vascular endothelial growth factor (VEGF). Depressive symptoms were measured with the 11-item version of the Centers for Epidemiologic Studies Depression (CES-D) Scale. Multiple logistic and linear regression and structural equation modeling were used to assess the relationships of interest. Results: Older cancer survivors and older adults without cancer experienced similar social network changes over time. In the overall NSHAP sample, adding new network members was protective of functional decline [odds ratio (OR): 0.64, 95% confidence interval (CI): 0.41-0.99] and experiencing a change in the frequency of contact was positively associated with functional decline (OR: 1.92, 95% CI: 1.15- 3.20). CRP levels were significantly 26% lower among cancer survivors who added two network members compared to those who added no network members. Experiencing a change in the frequency of contact was associated with a 19% higher level of TNF-α. Social support was directly associated with depressive symptoms and did not vary by cancer status. No mediation effects between social support, inflammation, and depressive symptoms were observed in path models and latent variable models. Conclusion: Together these results suggest that when new relationships form or when stable relationships remain strong over time, their effects on health are positive. Alternatively, negative health effects may emerge when relationships become weaker over time. This study provides significant and timely information to develop effective interventions to improve quality of life for cancer survivors and older adults.
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    REPRODUCTIVE AND HORMONAL FACTORS IN RELATION TO LUNG CANCER AMONG NEPALI WOMEN
    (2015) Vohra, Sanah; Dallal, Cher M; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Over 50% of global lung cancer incidence occurs in less developed regions (LDRs). Despite this, little is known regarding lung cancer risk factors in LDRs such as Nepal. Using data from a hospital-based case-control study conducted in B. P. Koirala Memorial Cancer Hospital (Nepal, 2009-2012), relationships between reproductive and hormonal factors and lung cancer were examined among women aged 23-85 years. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using multivariable logistic regression. Among postmenopausal women, those with a younger age at menopause (<45years; 45-49years) had an increased odds of lung cancer compared to those with an older (¡Ý50years) age at menopause (OR=2.14, 95%CI=1.09, 4.17; OR=1.93, 95%CI=1.07, 3.51, respectively), after adjusting for age and cumulative active smoking. This is the first study to characterize these relationships among Nepali women. Further research is needed to elucidate the role of age at menopause in lung cancer within this understudied population.
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    Association Between C-Reactive Protein and Serum 25-Hydroxyvitamin D: A Negative Acute Phase Reactant
    (2015) Verdin, Kelly; Lee, Sunmin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Objective: The aims of this study were to determine whether serum 25-hydroxyvitamin-D (25-OH-vitamin D) is a negative acute phase reactant and whether class of diagnosis modifies the association between C-Reactive Protein (CRP) and 25-OH-vitamin D. Methods: Multiple linear regression analysis was utilized to assess the association between CRP and 25-OH-vitamin D in 1,043 patients with acute and chronic diseases and normal volunteers. Results: After adjusting for confounding factors, the association between CRP and 25-OH-vitamin D was statistically significant. Class of diagnosis did not modify this association. Conclusions: 25-OH-vitamin D is demonstrated to be a negative acute phase reactant in this group of patients; Therefore, it is not an accurate marker of vitamin D status in the setting of inflammation. These findings support that 25-OH-vitamin D should be interpreted cautiously when CRP is elevated and that evaluating 25-OH-vitamin D in the context of CRP will improve accuracy of 25-OH-vitamin D interpretation.