Epidemiology & Biostatistics

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Emergency Preparedness: Knowledge and Perceptions of Latin American Immigrants
(1999) Carter-Pokras, Olivia; Zambrana, Ruth E.; Mora, Sonia E.; Aaby, Katherine A.
This paper describes the level of public emergency knowledge and perceptions of risks among Latin American immigrants, and their preferred and actual sources of emergency preparedness information (including warning signals). Five Latino community member focus groups, and one focus group of community health workers, were conducted in a suburban county of Washington D.C. (N51). Participants came from 13 Latin American countries, and 64.7% immigrated during the previous five years. Participants had difficulty defining emergency and reported a wide range of perceived personal emergency risks: immigration problems; crime, personal insecurity, gangs; home/traffic accidents; home fires; environmental problems; and snipers. As in previous studies, few participants had received information on emergency preparedness, and most did not have an emergency plan. Findings regarding key messages and motivating factors can be used to develop clear, prioritized messages for communication regarding emergencies and emergency preparedness for Latin American immigrant communities in the U.S.
Assessing Health Concerns and Barriers in a Heterogeneous Latino Community
(The Johns Hopkins University Press, 2006) Martinez, Iveris L.; Carter-Pokras, Olivia
Introduction. Major health issues and barriers to health services for Latino immigrants were identified through community-based participatory research in Baltimore city. Methods. In collaboration with community partners, five focus groups were conducted among Latino adults from 10 countries and health service providers. Findings. Priorities across groups included chronic diseases, HIV/AIDS and STDs, mental health, and the need for ancillary services. Community members and providers did not always agree on what health matters were of primary concern. Participants expected to receive health information at the point of service. Barriers to receiving health services and information span linguistic, financial, logistical, legal, and cultural matters. Conclusions. This formative research illustrates the complexity and interrelatedness of health priorities and barriers created by social issues such as employment, legal status, and related stressors.
A method for analyzing censored survival phenotype with gene expression data
(Springer Nature, 2008-10-06) Wu, Tongtong; Sun, Wei; Yuan, Shinsheng; Chen, Chun-Houh; Li, Ker-Chau
Survival time is an important clinical trait for many disease studies. Previous works have shown certain relationship between patients' gene expression profiles and survival time. However, due to the censoring effects of survival time and the high dimensionality of gene expression data, effective and unbiased selection of a gene expression signature to predict survival probabilities requires further study. We propose a method for an integrated study of survival time and gene expression. This method can be summarized as a two-step procedure: in the first step, a moderate number of genes are pre-selected using correlation or liquid association (LA). Imputation and transformation methods are employed for the correlation/LA calculation. In the second step, the dimension of the predictors is further reduced using the modified sliced inverse regression for censored data (censorSIR). The new method is tested via both simulated and real data. For the real data application, we employed a set of 295 breast cancer patients and found a linear combination of 22 gene expression profiles that are significantly correlated with patients' survival rate. By an appropriate combination of feature selection and dimension reduction, we find a method of identifying gene expression signatures which is effective for survival prediction.
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.
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).
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.
Hepatitis B vaccinations among Koreans: Results from 2005 Korea National Cancer Screening Survey
(Springer Nature, 2009-11-25) Juon, Hee-Soon; Choi, Kui Son; Park, Eun-Cheol; Kwak, Min-Son; Lee, Sunmin
Liver cancer is one of most commonly diagnosed cancers among Koreans. Chronic hepatitis B virus (HBV) infection is a major risk factor for liver cancer. HBV infection can be prevented by effective screening and vaccination programs. The purpose of this study is to examine the status of HBV infection and the predictors associated with HBV vaccination. The study population was derived from the 2005 Korea National Cancer Screening Survey (KNCSS). The KNCSS is an annual cross-sectional survey that uses a nationally-representative random sampling to investigate cancer screening rates. A total of 1,786 Koreans over 40 years of age participated in this study. Of all the participants, 5.9% reported HBV positive (HBsAg+, HBsAb-), 41.8% were HBV negative but protected (HBsAg-, HBsAb+), and 52.3% were unprotected (HBsAg-, HBsAb-). Among unprotected individuals (n = 934), 23.1% reported to have received the vaccination. About half of those who had vaccinations completed the 3-shot vaccine series. In multiple analyses, education, having private cancer insurance, alcohol use, having regular check-up, and doing regular exercise were associated with completed HBV vaccination. This study result suggests that we need a liver cancer education program to increase HBV awareness and to increase the liver cancer prevention message among low educated populations.
Survey on Horse-Related Injuries and Safety Practices in Maryland and Virginia
(2010) Bethune, Lisa Anne; Carter-Pokras, Olivia; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Horseback riding is a leading cause of sports injury. This thesis identifies socio-demographic characteristics of adults sustaining horse-related injuries, and factors associated with receipt of medical treatment and improvement of safety behaviors among those injured. A web-based, cross-sectional survey was conducted in Maryland and Virginia during July 1st - September 1st 2010 (n=908). Ninety-four percent (93.7%) of respondents had ever sustained a horse-related injury. Women and adults with ≥15 years of experience with horses had higher odds of injury than men and adults with <15 years of experience. Roughly half of the injured (48.2%) had received emergency treatment. The odds of receiving medical treatment for injuries occurring at a competition/show were 2.42 (1.08-5.44) times the odds of receiving medical treatment for injuries occurring at home. Provision of informational and emotional support from friends/family, healthcare professionals, or equine industry professionals was significantly associated with improving safety practices among the injured.
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.
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).
DIAGNOSTICS FOR MULTIPLE IMPUTATION BASED ON THE PROPENSITY SCORE
(2010) Wang, Jia; Zhang, Guangyu; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Multiple imputation (MI) is a popular approach to handling missing data, however, there has been limited work on diagnostics of imputation results. We propose two diagnostic techniques for imputations based on the propensity score (1) compare the conditional distributions of observed and imputed values given the propensity score; (2) fit regression models of the imputed data as a function of the propensity score and the missing indicator. Simulation results show these diagnostic methods can identify the problems relating to the imputations given the missing at random assumption. We use 2002 US Natality public-use data to illustrate our method, where missing values in gestational age and in covariates are imputed using Sequential Regression Multiple Imputation method.
Externalizing behavior in early childhood and body mass index from age 2 to 12 years: longitudinal analyses of a prospective cohort study
(2010-07-14) Anderson, Sarah E; He, Xin; Schoppe-Sullivan, Sarah; Must, Aviva
Background: Some evidence suggests that obesity and behavior problems are related in children, but studies have been conflicting and have rarely included children under age 4. An association between behavior problems in early childhood and risk for obesity could suggest that a common set of factors contribute to both. Our research objectives were to determine the extent to which externalizing behavior in early childhood is related to body mass index (BMI) in early childhood and through age 12, and to evaluate whether these associations differ by sex and race. Methods: Data from the NICHD Study of Early Child Care and Youth Development were analyzed. Externalizing behaviors at 24 months were assessed by mothers using the Child Behavior Checklist. BMI was calculated from measured height and weight assessed 7 times between age 2 and 12 years. Linear mixed effects models were used to assess associations between 24 month externalizing behavior and BMI from 2 to 12 years, calculate predicted differences in BMI, and evaluate effect modification. Results: Externalizing behavior at 24 months was associated with a higher BMI at 24 months and through age 12. Results from a linear mixed effects model, controlling for confounding variables and internalizing behavior, predicted a difference in BMI of approximately 3/4 of a unit at 24 months of age comparing children with high levels of externalizing behavior to children with low levels of externalizing behavior. There was some evidence of effect modification by race; among white children, the average BMI difference remained stable through age 12, but it doubled to 1.5 BMI units among children who were black or another race. Conclusions: Our analyses suggest that externalizing behaviors in early childhood are associated with children's weight status early in childhood and throughout the elementary school years, though the magnitude of the effect is modest.
Nitric oxide is negatively correlated to pain during acute inflammation
(Springer Nature, 2010-09-15) Hamza, May; Wang, Xiao-Min; Wu, Tongtong; Brahim, Jaime S; Rowan, Janet S; Dionne, Raymond A
The role that nitric oxide (NO) plays in modulating pain in the periphery is unclear. We show here, the results of two independent clinical studies (microdialysis and gene expression studies) and a pilot dose finding study (glyceryl trinitrate study), to study the role of NO in the early phase of acute inflammatory pain following oral surgery. The effect of ketorolac on NO production and nitric oxide synthase (NOS) gene expression was also studied. Microdialysis samples showed significantly higher levels of NO at the first 100 min compared to the last 80 minutes in the placebo treated group. In the ketorolac group, on the other hand, NO levels gradually decreased over the first 60 min but were similar to placebo over the later 100-180 min, with no significant change in NO level over time. The levels of NO were negatively correlated to pain intensity scores. Local infusion of the NO donor glyceryl trinitrate at the site of surgery, showed a small analgesic effect that did not reach statistical significance in the sample size used. While the gene expression of iNOS and eNOS were not up-regulated, 3 hours after surgery, nNOS was downregulated in both treatment groups and eNOS gene expression was significantly lower in the ketorolac group compared to the placebo group. Further, there was a positive correlation between the change in gene expression of nNOS and eNOS in the placebo goup but not in the ketorolac group. We suggest that at this early stage of inflammatory pain in man, NO is analgesic in the periphery. Further, ketorolac down-regulates eNOS gene expression.
Randomized trial of achieving healthy lifestyles in psychiatric rehabilitation: the ACHIEVE trial
(Springer Nature, 2010-12-13) Casagrande, Sarah S; Jerome, Gerald J; Dalcin, Arlene T; Dickerson, Faith B; Anderson, Cheryl A; Appel, Lawrence J; Charleston, Jeanne; Crum, Rosa M; Young, Deborah R; Guallar, Eliseo; Frick, Kevin D; Goldberg, Richard W; Oefinger, Meghan; Finkelstein, Joseph; Oladapo Fred-Omojole; Gennusa, Joseph V III; Fred-Omojole, Oladapo; Campbell, Leslie M; Wang, Nae-Yuh; Daumit, Gail L
Overweight and obesity are highly prevalent among persons with serious mental illness. These conditions likely contribute to premature cardiovascular disease and a 20 to 30 percent shortened life expectancy in this vulnerable population. Persons with serious mental illness need effective, appropriately tailored behavioral interventions to achieve and maintain weight loss. Psychiatric rehabilitation day programs provide logical intervention settings because mental health consumers often attend regularly and exercise can take place on-site. This paper describes the Randomized Trial of Achieving Healthy Lifestyles in Psychiatric Rehabilitation (ACHIEVE). The goal of the study is to determine the effectiveness of a behavioral weight loss intervention among persons with serious mental illness that attend psychiatric rehabilitation programs. Participants randomized to the intervention arm of the study are hypothesized to have greater weight loss than the control group. A targeted 320 men and women with serious mental illness and overweight or obesity (body mass index ≥ 25.0 kg/m2) will be recruited from 10 psychiatric rehabilitation programs across Maryland. The core design is a randomized, two-arm, parallel, multi-site clinical trial to compare the effectiveness of an 18-month behavioral weight loss intervention to usual care. Active intervention participants receive weight management sessions and physical activity classes on-site led by study interventionists. The intervention incorporates cognitive adaptations for persons with serious mental illness attending psychiatric rehabilitation programs. The initial intensive intervention period is six months, followed by a twelve-month maintenance period in which trained rehabilitation program staff assume responsibility for delivering parts of the intervention. Primary outcomes are weight loss at six and 18 months. Evidence-based approaches to the high burden of obesity and cardiovascular disease risk in person with serious mental illness are urgently needed. The ACHIEVE Trial is tailored to persons with serious mental illness in community settings. This multi-site randomized clinical trial will provide a rigorous evaluation of a practical behavioral intervention designed to accomplish and sustain weight loss in persons with serious mental illness.
Acculturation and BMI among Chinese, Korean and Vietnamese Adults in Maryland
(2011) Chen, Lu; Lee, Sunmin; Carter-Pokras, Olivia D; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Objective: To examine the relationship between acculturation and BMI among Asian Americans. Methods: Data of 847 Chinese, Korean and Vietnamese recruited for a health education program in Maryland were included. Acculturation was measured by the short version of Suinn-Lew Asian Self-Identity Acculturation Scale (SL-ASIA) and its individual components. Height and weight were measured by trained staff. Multiple linear regression was used to estimate the parameters of acculturation variables. Results: After adjusting for confounders, SL-ASIA (β=0.71, 95% CI: 0.15, 1.26), having education in the U.S (β=0.56, 95% CI: 0.01, 1.11), younger age of arrival (0-5 years: β=3.32, 95% CI: 1.84, 4.80, 6-10 years: β=1.55, 95% CI: 0.02, 3.07) and equal preference of Asian/American food in restaurants (β=0.92, 95% CI 0.38, 1.46) were associated with BMI. The association between acculturation and BMI was stronger among men than women, and weakest among Vietnamese. Conclusion: Acculturation is moderately associated with BMI among Asian Americans.
FACTORS ASSOCIATED WITH COMPLETION OF THE HUMAN PAPILLOMAVIRUS VACCINE SERIES AMONG HISPANIC AND NON-HISPANIC WHITE ADOLESCENT GIRLS IN THE UNITED STATES
(2011) Demarco, Maria Teresa; Carter-Pokras, Olivia; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Despite recommendations of three Human Papillomavirus (HPV) vaccine shots for all adolescent girls, only 29.1% of non-Hispanic Whites and 23.4% of Hispanics achieve completion. This study describes factors associated with completion of the HPV vaccine series among Hispanic and non-Hispanic White 13-17 year old girls who initiated the series. A secondary data analysis was performed of the cross-sectional 2009 National Immunization Survey-Teen survey. Despite similar initiation rates (one in five), Hispanic girls who had initiated the series (59.9%) were less likely to complete the series than non-Hispanic Whites (76.4%). After accounting for poverty status and home ownership, Hispanics were less likely to complete the HPV vaccine series. Factors associated with HPV vaccine series initiation were age at interview and age at HPV vaccine series initiation for Hispanics; and continuous health insurance since age of 11, mother's marital status, and number of children in the household for non-Hispanic Whites.
Subtype of depression as a moderator of response in the treatment of major depression with St John's wort
(2011) Ulbricht, Christine Marie; Lee, Sunmin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Objective: To evaluate the effect of the melancholic and anxious subtypes of depression on treatment response in the Hypericum Depression Trial. Methods: 340 adults with depression were classified according to depression subtype at baseline. Linear and logistic regression models examined the effects of depression subtype and treatment assignment on treatment response. Results: 64.41% of participants had melancholic depression and 71.76% had anxious depression. The linear regression model demonstrated that melancholic depression status at baseline and the interaction of treatment assignment and baseline melancholic status had significant effects on depression severity. The linear regression model showed significant effects only for treatment and anxious depression status at baseline on depression severity. Conclusion: While depression subtype appears to be related to certain clinical characteristics, this study was inconclusive and did not find melancholic or anxious depression subtypes to significantly moderate response to treatment with St John's wort, placebo, or sertraline.
COUNTY AND CENSUS TRACT SOCIOECONOMIC ATTRIBUTES OF ESOPHAGEAL ADENOCARCINOMA CASES SEER 15 (2000-2007)
(2011) Ghazarian, Armen Alex; Saksvig, Brit I; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Esophageal adenocarcinoma (EAC) incidence rates have increased among U.S. men. We examined associations between area-level socioeconomic attributes and stage at diagnosis, an important prognostic predictor of survival time. Logistic regression models were developed to estimate odds ratios (OR) adjusted for age, race, gender and year of diagnosis and 95% confidence intervals (CI) for localized and regional versus distant stage by census tract and county level socioeconomic attributes. At the county level, a high percent of foreign born population was associated with distant stage EAC: >15.4%-26.6%, (OR=1.15, 95% CI: 1.04-1.28) and >26.6% (OR 1.16, 95% CI: 1.03-1.31). Median household income from $40.8-$45.6K (OR=1.14, 95% CI: 1.01-1.28) was also associated with distant stage EAC. Conversely, residence in an urban county was associated with localized or regional stage EAC (OR=0.90, 95% CI: 0.82-0.98). Findings regarding area level disparities in EAC stage may inform cancer control efforts.
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.
SEMIPARAMETRIC AND NONPARAMETRIC ANALYSIS FOR LONGITUDINAL DATA ON THE RELATIONSHIP BETWEEN CHILDHOOD EXTERNALIZING BEHAVIOR AND BODY MASS INDEX
(2011) Wang, Kejia; He, Xin; Epidemiology and Biostatistics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
This thesis is an extension of the longitudinal data analysis of the association between externalizing behavior in early childhood and body mass index (BMI) from age 2 to 12 years conducted in Anderson et al. (2010). Externalizing behaviors problems are characterized by aggressive, oppositional, disruptive, or inattentive behaviors beyond those that would be expected given a child's age and development. The aim of the thesis is to estimate the children's BMI trajectory and to evaluate to what extent the externalizing behavior is related to BMI using semiparametric and nonparametric time-varying coefficient models. Some valuable insights into how the externalizing behavior and BMI are associated will be provided.