School of Public Health
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Note: Prior to July 1, 2007, the School of Public Health was named the College of Health & Human Performance.
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Item THE EFFECTS OF AGE, SARCOPENIA, AND RESISTANCE EXERCISE TRAINING ON MITOCHONDRIAL STRUCTURAL DYNAMICS IN SKELETAL MUSCLE(2024) Sapp, Catherine; Prior, Steven J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sarcopenia, the progressive, age-related loss of skeletal muscle mass, contributes to older adults’ risk of falls, hospitalization, and loss of independence. Mitochondrial dysfunction is a hallmark trait of aging and sarcopenia that may be mediated by changes to mitochondrial structure and location through the involvement of mitochondrial fusion, fission, and mitophagy (collectively referred to as mitochondrial quality control). Therefore, the purpose of this dissertation was to investigate whether mitochondrial quality control is altered by age or sarcopenia. The first study performed in a rat model of aging demonstrated that expression of proteins regulating fusion and mitophagy was higher in skeletal and cardiac muscle from old vs. young rats, and this was accompanied by reduced expression of fission proteins in skeletal muscle in the old rats. The second study included older humans and revealed no differences in mitochondrial quality control protein expression in skeletal muscle from sarcopenic vs. non-sarcopenic older adults. Furthermore, twelve weeks of resistance exercise training did not alter the expression of mitochondrial quality control proteins in the sarcopenic individuals. The third study investigated morphological differences in mitochondrial subpopulations and lipid droplets from the sarcopenic individuals from study two, both before and after resistance exercise training. Peripherally located and intermyofibrillar mitochondrial content and morphology did not change significantly after resistance exercise training. Lipid droplets from the intermyofibrillar region were similarly unchanged, but lipid droplets from the peripheral region had minor morphological changes after resistance exercise training. Together, this dissertation indicates that mitochondrial quality control proteins in skeletal and cardiac muscle are altered in response to aging and may contribute to mitochondrial dysfunction, but mitochondrial structural dynamics in skeletal muscle do not appear to be altered in older adults with a moderate degree of sarcopenia. This suggests that other, non-mitochondrial factors may play larger roles in the pathophysiology of sarcopenia. While the sarcopenic participants did improve muscular strength after resistance training, this was not accompanied by changes in mitochondrial content, morphology, or quality control. Therefore, resistance exercise training may not be an effective strategy to enhance mitochondrial structural dynamics in sarcopenia.Item HIPPOCAMPAL GLUCOSE TRANSPORT AND OXIDATION IN RESPONSE TO DISRUPTED BLOOD FLOW IN AN AGING RAT MODEL OF HEART FAILURE(2023) Pena, Gabriel Santiago; Smith, J. Carson; Kuzmiak-Glancy, Sarah; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The primary objective of this dissertation was to investigate, in a rodent model of cardiovascular disease promoted by transverse aortic constriction (TAC), whether cerebral hypoperfusion stemming from chronic high pulsatile blood flow, and cerebral hypoperfusion stemming from low cerebral blood flow differentially affected hippocampal glucose transport and hippocampal mitochondrial function. We first, characterized the changes in right and left carotid hemodynamics and diameter in response to TAC and in a SHAM control group at three different time points (20-, 30-, and 40 weeks) post-surgery. Then, right, and left hippocampal mitochondrial content and substrate oxidation were investigated, and protein expression of glucose transporters and mitochondrial quality control markers were quantified. In this study, both the SHAM and TAC conditions included male and female rats to address possible sex differences. We report that all time points within TAC, right carotid blood flow velocities and pulsatility were greater than the left, but did not worsen over time. No differences in mitochondrial content were found within TAC nor between TAC and SHAM, but within TAC animals there were impairments in right hippocampal coupled and uncoupled respiration when compared to the left. When compared to the SHAM controls, right and left hippocampi of TAC animals had higher protein expression of mitochondrial quality control markers, but no differences in glucose transporter expression were found. Thus, while both high blood flow and/or pulsatility as well as low cerebral blood flow may lead to brain hypoperfusion, the metabolic consequences of the two may not be the same. The results from this dissertation contribute to the expanding literature characterizing the intersection between cardiovascular disease and neurodegeneration.Item ASSESSING THE IMPACT OF POLYPHARMACY ON THE ELDERLY USING NATIONALLY REPRESENTATIVE SURVEY DATA(2023) Eschenlauer, Adam; Franzini, Luisa; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Polypharmacy is a growing issue that affects individuals of all ages yet is most prevalent among patients aged 65 and older with chronic comorbidities. Although integral to most treatment plans, pharmaceutical intervention may negatively impact one’s health when five or more medications are taken daily. Given the concurrent rise in elderly population and polypharmacy prevalence, it is vital that we better understand the impact that concomitant medication use has on this vulnerable segment of population.Purpose: This research examines the factors leading to polypharmacy among the elderly population and explores its various impacts on healthcare utilization. Data and Methods: This study uses Medical Expenditure Panel Survey (MEPS) Data. Fixed-Effects regression analyses examine relationships between predictive factors and polypharmacy, polypharmacy and expenditures, and polypharmacy and utilization. Classification models assess the ability of machine learning to correctly predict utilization within the sample population. Key Results: Aside from clinical indicators, demographic and socio-economic factors play a role in determining polypharmacy status. Polypharmacy risk is higher for women (1.088, p < 0.001), high income individuals (1.107, p < 0.01), and those covered by Medicaid (1.110, p < 0.001). Conversely, married individuals (0.930, p < 0.001) and non-Hispanic Blacks (0.864, p < 0.001) have reduced risks of polypharmacy. We find polypharmacy to be associated with higher total (p < 0.001), inpatient (p < 0.01), outpatient (p < 0.01), and prescription medical expenditures (p < 0.001) when holding other predictors constant. We find the risk of hospitalization to be higher for polypharmacy patients (RR: 1.592, p < 0.001) than nonpolypharmacy patients after controlling for multimorbidity and medication class. Lastly, machine learning algorithms classify admissions with an overall accuracy of 84.9%; however, a low true positive rate (TPR) of 41.7% and high true negative rate (TNR) of 96.5% indicate best performance is achieved in predicting non-admissions. Conclusion: Polypharmacy is associated with several non-clinical factors and has a statistically significant impact on medical expenditures and admissions. Though imperfect, predictive analysis methods improve our ability to identify patients at risk for admissions and present a potential opportunity for future applications aimed at reducing utilization and costs.Item ASSESSING IMPACT OF CANCER AND DEPRESSION ON THE FINANCIAL HEALTH OF MIDDLE AGED AND OLDER AMERICANS(2023) Omeaku, Nina; Boudreaux, Michel; Health Services Administration; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation examines the impact of cancer on financial outcomes for individuals aged 50 and older and documents how this relationship varies by sex and race/ethnicity. I then turn to the impact of depression on out-of-pocket medical spending among those with a history of cancer. Findings suggest cancer can have a deleterious effect on the financial outcomes of those who are diagnosed with cancer. Out-of-pocket spending rises in the year of diagnosis, reduced earnings persist beyond diagnosis, and depression increases out-of-pocket spending. I fail to find evidence that the relationship between cancer and financial outcomes is moderated by sex or race-ethnicity.Item FUNCTIONAL CONNECTIVITY PATTERNS ASSOCIATED WITH AGING, PHYSICAL ACTIVITY, AND GENETIC RISK FOR ALZHEIMER’S DISEASE IN HEALTHY HUMAN BRAIN NETWORKS.(2017) Chirles, Theresa Jeanne; Smith, Carson J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Leisure time physical activity (PA) and exercise training help to improve and maintain cognitive function in healthy older adults and in adults with the APOE-ε4 allele, a genetic risk for Alzheimer’s Disease (AD). Earlier work finding increased functional connectivity in the Default Mode Network (DMN) after a 12-week walking intervention in 16 older adults with mild cognitive impairment is presented in Chapter 3. The primary dissertation study investigating differences in brain function depending on PA level and genetic risk for AD prior to changes in cognition is presented in Chapters 4-6. Useable resting state and anatomical MRI scans were collected from 69 healthy adults (22-51 years) as well as saliva for APOE genotyping (carriers defined as homozygotes or heterozygotes of the ɛ4 allele) and responses to the Paffenbarger Physical Activity Questionnaire (High PA >1500 kcal, Low PA <1500 kcal per week). The following network measures of functional connectivity were calculated: global efficiency; node strength of Default Mode Network (DMN) and Fronto-Parietal Network (FPN) hubs and hippocampal subsections; and long-range connectivity of the medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) in the DMN. Multiple linear regression analysis revealed statistically significant results for the long-range connectivity of the left PCC, a prominent hub of the DMN, and left mPFC. The differences in projected trajectories of the connectivity are potentially reflective of the compensatory time-course in our participants based on interactions of PA level and APOE status. The Low PA non-carriers had a positive slope indicating increased connectivity with age while carriers and non-carriers in the High PA category had horizontal aging trajectories. PA is associated with cognitive reserve (CR), a term describing the protection and adaptation of cognitive processes through neural efficiency and compensation mechanisms, and it is possible the Low PA non-carriers exhibited compensatory increases in connectivity of the left mPFC-PCC earlier than High PA study participants due to lower levels of CR. The promising findings that rs-fMRI can be used as an early detection of brain changes sensitive to PA levels and APOE-ɛ4 status are critical to the research and treatment of AD.Item 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.Item Risk prediction models for hip fracture: parametric versus Cox regression(2013) Loo, Geok Yan; Ting Lee, Mei-ling; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hip fracture is a public health burden due to high morbidity, mortality and cost. Risk prediction models can aid clinical decision-making by identifying individuals at risk. Objective: To build risk prediction model for incident hip fracture using Weibull regression and compare this with Cox regression model. Method: The Study of Osteoporosis prospectively collected risk factors were used to build a risk prediction model for first hip fracture using Threshold regression with Wiener process. Similar predictors were fitted using Cox regression for comparison. Results: There were 632 first hip fractures. Age, bone density, maternal and personal prior fractures were significant risk factors for hip fracture. Weibull had better goodness of fit, higher D-statistic and R-squared values than the exponential. Models did not differ in c-index and ten-fold cross validation showed similar areas under the ROC curves. Conclusion: Parametric and Cox models were comparable. External validation of the prediction model is required.Item APPLICATION OF DIFFUSION OF INNOVATIONS: A DESCRIPTIVE PILOT STUDY ON THE PERCEPTIONS OF HOME MONITORING SYSTEMS BY ADULTS 45 TO 64 YEARS OF AGE(2012) Tran, Quynh; Holt, Cheryl L; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)BACKGROUND: Improving the function and quality of life of older adults is a key objective identified in Healthy People 2020. Prevention efforts that address the needs of older adults while respecting their desire to remain independent are critical towards meeting this objective. Home monitoring systems (HMS) are a relatively new consumer health technology product that holds promise in enabling independence among seniors in their homes by delaying admittance into institutionalized settings and yet it struggles with low adoption rates in the consumer market. The purpose of this pilot study was to detect and measure the anticipated innovation attributes of HMSs to inform its positioning and promote faster diffusion rates by describing potential adopters among adults 45 to 64 years of age. METHODS: An existing survey was modified to collect perceptions of three anticipated attributes of innovation as they relate to the intention of adopting an HMS as a preventive health behavior. The survey modification was theoretically based on the Diffusion of Innovations (DOI) piloted among residents of Chevy Chase and Bethesda, Maryland (N=71). Logistic regression and Pearson correlation analyses were used to detect evidence to support whether perceived relative advantage, compatibility and complexity and demographic variables were associated with the intention to adopt an HMS in the future. RESULTS: Majority of participants were highly educated, perceived themselves to be in very good health, were or had been caretakers and intended to adopt an HMS in the future. Evidence was found supporting the DOI variables were positively correlated with the intention to adopt an HMS at statistically significant levels (p < .01 and .05). However, high ORs and wide 95% CIs caution the use of these variables as precise predictors of innovativeness and small sample size inhibits the interpretation that a pure statistical relationship exists. Additional findings included the potential of using caretaker status as a predictive variable and purchasing an HMS directly from the manufacturer emerged as an insight into consumer behavior. CONCLUSION: Findings from this study can help us understand how assistive technologies like HMSs are perceived and describe characteristics of early adopters. These preliminary insights can inform future research and improve efforts to encourage faster rates of adoption, particularly in the consumer marketplace where rapid diffusion of promising technologies can have the greatest impact on improving health outcomes for a new aging population.Item Examining the role of stressful life events on cognition and determining mediating and moderating pathways among postmenopausal women(2011) Bibeau, Wendy; Young, Deborah R; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)BACKGROUND: Major life events, largely considered to be a source of great stress, are an inevitable process of the life span. Preliminary evidence suggests that the stress arising from major life events may serve as a risk factor for cognitive function decline. Evidence also indicates external (e.g., physical activity) and internal factors (i.e., psychological variables) can attenuate the physiologic effects of stress. Thus, there may be two important pathways through which stress affects health. PURPOSE: The primary aim of this dissertation was to investigate the independent and interactive effects of stressful life events on cognitive function among a sample of postmenopausal women. In addition, the possible moderating and or mediating role of external and internal factors on the relationship between stressful life events and cognitive function were examined. METHODS: Data from the Women's Health Initiative Memory Study, a randomly selected subset of the Women's Health Initiative Hormone Trial, were analyzed. To control for any treatment effects, only data from participants randomized into the placebo groups were pooled and used for all analyses, leaving a total of 3775participants. All participants had five data collections points, including baseline through four years of follow-up. Linear mixed effects models were used to answer all prospective research questions. Moderation and mediation models were used to determine presence of effect modification or mediation of external or internal variables. RESULTS: Our results appear to indicate that there was a negative relationship between stressful life events and cognitive function scores. Reporting an ill spouse/partner was associated with lower cognition scores compared to those without reporting a spouse/partner (B = -0.68, p < 0.0001). Exposure to three or more stressful life events at every data collection period was also associated with lower cognitive function scores (B = -0.61, p = 0.021). External factors did not appear to moderate this negative relationship; however, internal factors such as optimism, hostility, and negative expressiveness did. Specifically, exposure to more stressful life events was associated with less favorable psychological states, which in turn, were associated with lower cognitive function scores. CONCLUSION: Our results appear to lend support that exposure to certain life events and repeated exposure of stressful life events is associated with lower cognitive functioning. In addition, our findings provide modest evidence that psychological mechanisms are an important pathway through which stressful life events affect cognitive functioning over time among a representative sample of post-menopausal women. While stressful life events are largely unavoidable, the associated increased risk of cognitive function decline may be in part offset by various psychological factors.Item Aging Related Differences in Hand Intrinsic and Extrinsic Muscles for Hand Dexterity: An MRI Investigation(2009) Hsu, Jeffrey; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hand dexterity is crucial for humans to interactions with the external environment. Many activities of daily living (ADLs) such as pressing, grasping, writing and typing would be unattainable without a skillfully and proficiently functioning hand. Sexagenarians and older often experience difficulties in hand dexterity, which seriously impair their ability to perform ADLs. This study described the aging-related changes in hand muscle size and dexterity; and addressed the conflicting literature regarding the extent of atrophy to either the intrinsic or extrinsic hand muscles in the elderly. The overall hypotheses for this study were 1) that elderly adults show an aging-related decrease in hand muscle size and strength, especially a greater decrease in the intrinsic hand muscles, 2) elderly adults show an aging-related decrease in hand dexterity and 3) hand muscle size and strength are positively related to hand dexterity. This study examined hand muscle sizes with magnetic resonance imaging (MRI) and examined hand strength and other functional measures. This study found aging-related decreases in muscle size, muscle strength, hand dexterity. Furthermore, intrinsic muscles showed a greater aging-related decrease in volume and strength as compared to the extrinsic muscles. When examining relationships, muscle strength was positively correlated to multi-finger synergy and finger dependence. Also, muscle size was positively related to performance on clinical hand dexterity tests. This supports the strength-dexterity equivalence hypothesis.