Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
12 results
Search Results
Item IS THE CURRENT DEFINITION OF THE METABOLIC SYNDROME A USEFUL TOOL FOR THE DETECTION OF CARDIOVASCULAR DISEASE IN NON-HISPANIC BLACKS?(2010) Rodriguez, Omayra Isabel; Song, Jiuzhou; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Blacks in the country suffer from higher prevalences of obesity, diabetes, hypertension and cardiovascular disease compared to whites. Paradoxically, they have the lowest prevalence of the Metabolic Syndrome (MS) compared to whites and Mexican Americans. This is likely due to the fact that blacks tend to have lower triglycerides (TG) and higher high density cholesterol (HDL) levels. We challenged the current lipid criteria established by the Adult Treatment Panel III for the detection of the MS and set out to find more appropriate TG and HDL cutoffs to detect the MS in blacks. Using data from the National Health and Nutrition Examination Survey from 1999-2006, we identified that a more appropriate TG cutoff for blacks to detect the MS is 110 mg/dL but were not able to identify more suitable HDL cutoffs. Our results confirm that race/ethnic-specific criteria should be established for the detection of the MS across racial/ethnic groups.Item Investigating Neighborhood Walkability and its Association with Physical Activity Levels and Body Composition of a Sample of Maryland Adolescent Girls(2010) Jones, Lindsey Irene; Young, Deborah R; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recent ecologic studies have begun to focus on characteristics of the built environment that influence physical activity (PA). Specifically, neighborhood walkability is emerging as an important determinant of PA in adults. At this point in time, there is conflicting evidence on how neighborhood walkability influences the PA levels of adolescents. The aim of this study was to investigate the relationship between individual's neighborhood walk score and individual's body mass index, body fat percentage, weight status, PA levels and meeting PA guidelines in a sample of adolescent girls. Additional analysis investigated the correlation between two objective measures of neighborhood walkability. This analysis was unable to show an association between PA levels or body composition of adolescent girls from the TAAG Maryland field site. Neighborhood walkability as assessed by the website walkscore.com was positively correlated with a GIS derived walkability index (r=.63 p<.0001).Item Association between Allostatic Load and Arthritis in NHANES Adults(2010) Scully, Lynn; Lee, Sunmin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Objective: To examine the cross-sectional association between allostatic load and arthritis using data from the National Health and Nutrition Examination Survey (NHANES). Methods: Complete data on 7,714 adults were included in the analysis. An allostatic load (AL) index, comprising of multiple regulatory systems, was calculated from 11 biomarkers. Multivariate logistic regression was used to estimate the odds ratio (OR) for the association between allostatic load and arthritis, while accounting for confounders. Results: Significant positive associations were found between both continuous allostatic load (OR=1.12, 95% CI= 1.08-1.17) and the two highest quartile categories of AL and arthritis compared to the lowest quartile (quartile 3: OR=1.73, 95% CI=1.38-2.17, quartile 4: OR=1.79, 95% CI=1.41-2.26), after adjusting for confounders. The subscales of the inflammatory (OR=1.27, 95% CI=1.15-1.40) and metabolic system (OR=1.20, 95% CI=1.13-1.28) were also significant predictors. Conclusions: Cumulative biological risk is a plausible mechanism that is associated with arthritis.Item Identification of Factors That Relate to Gestational Age in Term and Preterm Babies Using 2002 National Birth Data(2009) Hammad, Hoda Tarek; Zhang, Guangyu; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Infant mortality and other subsequent handicaps have been found to be correlated with preterm births. The purpose of this study is to investigate which factors relate to gestational age in term and preterm babies using the 2002 Public-Use Natality data file. Using this data, an exploratory data analysis of both the important discrete and continuous variables will be conducted to obtain a general idea of the data set. This will be followed by the use of regression models to determine which explanatory variables best relate to gestational age. The results can be used to establish guidelines for monitoring and treatment plans for expectant mothers who are most susceptible to preterm labor.Item TIME TRENDS IN OVERALL DAILY PHYSICAL ACTIVITY AND CARDIOVASCULAR DISEASE RISK FACTORS BY ORGANIZED PHYSICAL ACTIVITY PARTICIPATION IN ADOLESCENT GIRLS(2009) Phillips, Jennifer; Young, Deborah Rohm; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Many youth are involved in organized physical activity (PA); however, the impact of these activities on daily PA, body fat, and cardiovascular disease (CVD) risk factors is not well understood. Purpose: To compare the overall daily PA and CVD risk factors of girls who participate in organized activities to non-participants throughout adolescence. Methods: Data from the National Heart, Lung, and Blood Institute Growth and Health Study, a 10-year observational study of Black and White girls (N=2379), were analyzed. Organized PA was defined as participation in classes/lessons and sports (0, <4, 4-19.99, ≥20 MET times/wk). Outcomes included daily PA (3-day diary), body fat (bioelectrical impedance analysis), lipids, glucose, insulin, and blood pressure. Longitudinal data were examined for each outcome using a mixed model with repeated measures. Girls were also categorized by the number of years they reported ≥4 MET times/wk of organized PA. Outcomes and risk clustering at 18-19y were evaluated with ANOVA and logistic regression, respectively, by number of participation years. Results: Organized PA and participation*time*race were related to change in daily PA and body fat (p < 0.0001). Although daily PA declined for Black girls, those with ≥20 MET times/wk had higher PA levels than all other girls (p < 0.0001). Change differed by sports participation in White girls (p=0.019); those involved ≥20 MET times/wk demonstrated better maintenance of daily PA. Black girls with ≥20 MET times/wk had significantly lower body fat than non-participants (p=0.002).White non-participants had higher body fat than those with 4-19.99 MET times/wk (p=0.006). Accumulated organized PA was related to daily PA and body fat at 18-19y. Girls who never reported participation had significantly lower daily PA at 18-19y than all other groups (p < 0.02), and significantly higher body fat at 18-19y compared to girls who reported 4y of sports participation (p=0.038). Organized PA was not related to change in other CVD risk factors or risk factor clustering at 18-19y (OR=1.05, 95% CI=0.87-1.27, p=0.59). Conclusion: Organized PA was related to daily PA and body fat for Black and White girls throughout adolescence. Appealing options should be made available and participation encouraged.Item Appropriate Waist Circumference Cutoff Values for the Diagnosis of Metabolic Syndrome in Mexican American Adults(2009) Sarafrazi, Neda; Jackson, Robert T; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Metabolic syndrome increases the risk of cardiovascular disease and diabetes. The International Diabetes Federation (IDF) recently proposed new criteria for the diagnosis of metabolic syndrome, which requires the presence of central obesity as measured by ethnic specific waist circumference (WC) cutoff values. Currently, no specific WC thresholds for diagnosis of central obesity in Hispanics are available. The objectives were to determine the appropriate gender specific WC thresholds for diagnosis of central obesity in Mexican American adults and to estimate the prevalence of metabolic syndrome using IDF definition with and without the modified WC in this population. Data from 3265 Mexican American adults aged 20-80 years who participated in the National Health and Nutrition Examination Survey 1999-2006 were used. The prevalence of metabolic syndrome was compared using IDF criteria with and without the modified waist circumference. Receiver operating characteristic curve analysis suggested that yielding at least 80% sensitivity, the WC value of 90 cm in both genders was more appropriate in predicting the presence of two or more metabolic syndrome risk factors in this population. Based on this cutoff, there was 34% reduction in the prevalence of central obesity in women (82.5% to 54.2%). The age adjusted prevalence of metabolic syndrome decreased from 58.4 to 48.2%. The metabolic syndrome was more common among Mexican American men than women (55.8% in men versus 37.8% in women, P =0.0003). Our findings provided a practical guidance in the assessment and screening of central obesity and metabolic syndrome in Mexican Americans.Item Development and Evaluation of New Accelerometer Cut Points for Adolescent Girls(2009) Kuo, JoAnn; Young, Deborah R; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Current negative trends in adolescent disease risk factors (e.g., overweight) may be related to physical activity. To study these relationships using accelerometers, how to estimate physical activity from accelerometer counts must be better understood. PURPOSES: (1) To develop new accelerometer cut points for estimating physical activity using disease risk factors as criteria. (2) To evaluate how estimates of physical activity using these newly developed cut points agree with comparison measures (i.e., a previously suggested cut point and self-report physical activity recall questionnaires). METHODS: National Health and Nutrition Examination Survey (NHANES) and Trial of Activity for Adolescent Girls (TAAG) data were examined. New cut points were developed using iterative correlations and signal detection and receiver operating characteristic (ROC) curves. To identify new cut points, potential cut points were identified in a development sample and validated in an evaluation sample. Agreement between new cut points and comparison measures was examined using concordance correlation coefficients, Bland-Altman plots, McNemar's tests, and proportions of agreement. RESULTS: Using the correlation method, two new combinations of light, moderate, and vigorous intensity cut points were identified in NHANES (1900, 4300, and 10000 counts/min and 1900, 4000, and 5000 counts/min) and two in TAAG (1450, 1950, and 2450 counts/30 sec and 1050, 1550, and 2050 counts/30 sec). Using the signal detection/ROC curve method, eleven new cut points were identified in NHANES (ranging from 100 to 2300 counts/min) and three in TAAG (ranging from 100 to 200 counts/min). Concordance correlation coefficients for minutes of activity with a previously suggested cut point tended to be stronger (≥ 0.60) with higher cut points (≥ 2300 count/min), while those with questionnaires were less than 0.10 or the 95% confidence intervals included zero. One new cut point (1800 counts/min) was similar (p = 0.6) to a comparison measure for classifying meeting recommendations. CONCLUSIONS: Some cut points may be more strongly associated with disease risk factors than previously suggested cut points developed using oxygen consumption, but associations are not strong. The new cut points and comparison measures may be measuring different aspects of physical activity, as they were in poor agreement.Item Effects of birthplace, language and length of time in the U.S. on receipt of asthma management plans among U.S. adults with current asthma(2009) Williams, Sonja; Carter-Pokras, Olivia; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Approximately 7% of the adult population in the United States suffers from asthma and only 32% of those adults have an asthma management plan, which is an important component in asthma management. Racial/ethnic minorities have higher rates of asthma and lower rates of good asthma management. There is a lack of research in examining how foreign birth and other proxy measures of acculturation may affect long term management of asthma. Using data from both the 2002 and 2003 National Health Interview Survey, this secondary data analysis examined the relationship between the receipt of asthma management plans among 18-64 year old adult asthmatics by birthplace, length of time in the U.S., and language of interview. Hispanic/Latino participants who spoke English during the interview had a 3.43 times greater odds of having an asthma management plan when compared to those who spoke Spanish (95% CI: 1.97-5.98).Item Missing Data Analysis: A Case Study of a Randomized Controlled Trial(2009) Patzer, Shaleah Mary Murphy; Zhang, Guangyu; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Missing data is a pervasive problem in the analysis of many clinical trials. In order for the analysis of a study to produce unbiased estimators, the missing data problem must be addressed. First, the missing data pattern must be established; second, the missingness mechanism must be determined; and third, the most appropriate imputation method for imputing the missing values must be found. The purpose of this paper is to explore the imputation methods best suited for the missing data from the Diet and Exercise for Elevated Risk Trial (DEER) in a secondary analysis of the data. The missingness pattern in the data set is arbitrary and the missingness mechanism is MAR. A simulation study suggests that the two best methods for imputation are subject-specific mean imputation and multiple imputation. I conclude that mean imputation is the best method for handling missing data in the DEER data set.Item Environmental influences on physical activity and obesity in African American adolescents-a multilevel perspective(2009) Yan, Fang Alice; Beck, Kenneth; Public and Community Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Prevalence of obesity among adolescents is increasing at an alarming rate. Currently, 34% of all 12-19 year olds are either at risk for overweight or are overweight. Without a comprehensive understanding of the myriad of environmental factors that influence physical activity, we cannot effectively curb the rising rates. Methods: The objective of this study is to evaluate the direct and indirect effects of individual, built, and psychosocial environmental factors on the body mass index (BMI) of African American adolescents, and to assess how the relationships may be mediated by physical activity (PA) levels in an urban setting. A cross-sectional sample of 350 Students (grades 9-12) was drawn from two urban magnet high schools in Baltimore City. The outcome measurements cover a broad array of variables, including BMI, walking behavior, and overall PA. The independent variables are measures of three environments and individual socio-demographic status. The hierarchical linear model analysis was employed. In addition, the mediation analysis was conducted to examine the mediating effect of PA levels. Results: The majority of the sample was African American (69%) and female (58%) with 40% at risk of overweight or overweight. After adjustment for individual socio-demographic factors, living in more hazardous neighborhoods was positively associated with moderate-to-vigorous physical activity (MVPA) and walking for transportation but not with BMI. Densities and proximities of destinations were not associated with BMI. Access to school and museums within 0.25 mile, and grocery stores, retail and shopping, post offices and mix of destinations within 0.5 mile and beyond was positively associated with participation in walking. In addition, densities of fast food restaurants, parks and recreation within 1 mile and 1.5 mile were associated with increased walking. Closer proximity to schools and museums increased both student's MVPA level and their walking trips. Green space coverage within 0.25 mile distance was associated with decreased BMI. In addition, the percentage of green space coverage around homes was not associated with physical activity. Physical activity did not mediate either the destination densities and proximity or the greenness on BMI. Conclusion: The findings support the importance of focusing on places rather than the individuals who live in those places. Increasing the diversity of walkable destinations may contribute to adolescents doing more transport-related walking and achieving recommended levels of physical activity. In general, ecologic approaches to obesity prevention need to focus on urban design and food availability.