Epidemiology & Biostatistics
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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 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.