Browsing by Author "Steele, Gregory K."

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    Advanced Modeling of Longitudinal Spectroscopy Data
    (2014) Kundu, Madan Gopal; Harezlak, Jaroslaw; Randolph, Timothy W.; Sarkar, Jyotirmoy; Steele, Gregory K.; Yiannoutsos, Constantin T.
    Magnetic resonance (MR) spectroscopy is a neuroimaging technique. It is widely used to quantify the concentration of important metabolites in a brain tissue. Imbalance in concentration of brain metabolites has been found to be associated with development of neurological impairment. There has been increasing trend of using MR spectroscopy as a diagnosis tool for neurological disorders. We established statistical methodology to analyze data obtained from the MR spectroscopy in the context of the HIV associated neurological disorder. First, we have developed novel methodology to study the association of marker of neurological disorder with MR spectrum from brain and how this association evolves with time. The entire problem fits into the framework of scalar-on-function regression model with individual spectrum being the functional predictor. We have extended one of the existing cross-sectional scalar-on-function regression techniques to longitudinal set-up. Advantage of proposed method includes: 1) ability to model flexible time-varying association between response and functional predictor and (2) ability to incorporate prior information. Second part of research attempts to study the influence of the clinical and demographic factors on the progression of brain metabolites over time. In order to understand the influence of these factors in fully non-parametric way, we proposed LongCART algorithm to construct regression tree with longitudinal data. Such a regression tree helps to identify smaller subpopulations (characterized by baseline factors) with differential longitudinal profile and hence helps us to identify influence of baseline factors. Advantage of LongCART algorithm includes: (1) it maintains of type-I error in determining best split, (2) substantially reduces computation time and (2) applicable even observations are taken at subject-specific time-points. Finally, we carried out an in-depth analysis of longitudinal changes in the brain metabolite concentrations in three brain regions, namely, white matter, gray matter and basal ganglia in chronically infected HIV patients enrolled in HIV Neuroimaging Consortium study. We studied the influence of important baseline factors (clinical and demographic) on these longitudinal profiles of brain metabolites using LongCART algorithm in order to identify subgroup of patients at higher risk of neurological impairment.
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    Assessment of Risk Behaviors in Patients With Opioid Prescriptions: A Study of Indiana’s Inspect Data
    (Wiley, 2017-12) Greene, Marion S.; Chambers, Robert Andrew; Yiannoutsos, Constantin T.; Wright, Eric R.; Steele, Gregory K.; Zollinger, Terrell W.; Health Policy and Management, School of Public Health
    Background and Objectives Prescription Drug Monitoring Programs (PDMPs) can serve as screening tools and support the clinical decision‐making process in patients receiving opioids. The objective of the study was to utilize 2014 INSPECT (Indiana's PDMP) data to identify factors that increase patients’ likelihood to engage in opioid‐related risk behaviors. Methods Based on a literature review, four risk behaviors were identified: Receiving >90 morphine milligram equivalents (MME), having >4 opioid prescribers, obtaining opioids from >4 pharmacies, and concurrent use of opioids and benzodiazepines. Two binary logistic regression analyses (engaging in at least one risk behaviors; engaging in all four risk behaviors) and an ordinal regression analysis (engaging in 0–4 risk behaviors) were conducted to identify factors associated with these opioid‐related risk behaviors. Results Of the 1,538,120 unique opioid patients included in the study, 18.4% engaged in one, 5.3% in two, 1.6% in three, and .4% in all four risk behaviors. Depending on the model, prescribing a second monthly opioid increased patients’ odds to engage in risk behaviors by a factor of 10 or more and prescribing two or more benzodiazepines annually increased the odds at least 13‐fold. Conclusions and Scientific Significance About one‐fourth of all patients consuming opioids engaged in one or more risk behaviors; higher number of opioid prescriptions and addition of even a small number of benzodiazepine prescriptions dramatically increased these odds. PDMPs can be helpful in identifying opioid users at high‐risk for misuse. This information could be used to target efforts to reduce the prescription drug epidemic.
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    The effect of cigarette smoking on the virulence of streptococcus mutans caries and cardiovascular diseases-epidemiological analysis and in vitro studies
    (2010) Zheng, Cunge; Gregory, Richard L.; Windsor, L. Jack; Kowolik, Michael J.; Steele, Gregory K.; Holt, Robert G.
    The impact of tobacco smoking on human health is well documented. The influence of smoking on tooth loss and cardiovascular diseases was investigated in the current study via both epidemiology and in vitro studies. From analyzing the 2006 Behavioral Risk Factor Surveillance System (2006 BRFSS) database, we confirmed that smoking was significantly associated with the number of teeth lost in a dose-dependent manner and smoking cessation reduced the risk when compared to those subjects continuing to smoke. In addition, the virulence factors related to caries were compared between Streptococcus mutans and Streptococcus gordonii in response to cigarette smoking condensate (CSC) treatment. We observed that S. gordonii was more susceptible to CSC treatment than S. mutans. CSC significantly enhanced S. mutans sucrose-dependent and independent adherence. Western blot assays revealed that several bacterial surface proteins including glucosyltransferase (GTF), glucan-binding proteins and antigen I/II, were significantly upregulated for the treated S. mutans. These findings suggested that the oral environment with CSC may favor a cariogenic dominant composition, which may increase the risk for smokers to develop caries. We also found that smoking and oral health status modified each other and synergistically increased the risk of CVD and this joint effect was more pronounced among the youngest age group using the 2006 BRFSS database. To further understand the joint effect, we conducted an in vitro study to investigate bacterial attachment to fibronectin and endothelial cells in response to smoking condensate treatment. Our study clearly demonstrated CSC significantly enhanced S. mutans attachment to both soluble and immobilized fibronectin as well as endothelial cells. Furthermore, our data suggested that bacteria possessed several adhesins that bound to host tissues and endothelial cells also had multiple receptors for bacterial attachment. Among these adhesins, antigen I/II seemed essential for bacterial attachment to endothelial cells without CSC. The knowledge of bacterial attachment to host tissues in the presence of CSC may help in developing different preventive or therapeutic strategies against attachment and colonization of the host by S. mutans.
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    The risks and consequences of opioid misuse
    (2018-05-22) Greene, Marion Siegrid; Zollinger, Terrel W.; Steele, Gregory K.; Yiannoutsos, Constantin T.; Chambers, R. Andrew; Vest, Joshua R.; Wright, Eric R.
    Opioid misuse and addiction has been widely identified as a public health problem, contributing substantially to the nation’s morbidity and mortality. Over the past two decades, misuse of prescription opioids pain relievers has substantially increased; heroin use has resurged; and, more recently, abuse of high-potency synthetic opioids such as fentanyl have fueled the epidemic. Nearly 12 million Americans (or 4.4%) aged 12 and older misused some type of opioid (prescribed or illegal) in the past year. Furthermore, the percentage of substance use treatment admissions attributable to opioids nearly doubled in the U.S., from 20.8% in 2000 to 40.5% in 2015. The purpose of this dissertation research was to investigate associations between prescription pain reliever use and subsequent negative health outcomes, including opioid misuse or addiction, and neonatal abstinence syndrome. This research focused on three specific aims: Specific Aim #1: Examine heroin use among Indiana’s substance use treatment population to measure the extent, trends, and patterns of use, as well as to assess the relationship between prescription opioids and subsequent heroin use; Specific Aim #2: Analyze 2014 INSPECT (Indiana’s prescription drug monitoring program) data to identify factors that increase patients’ likelihood to engage in opioidrelated risk behaviors; and Specific Aim #3: Review U.S. trends in neonatal abstinence syndrome (NAS) incidence from 2008-2014, measure regional variability, and identify personal and environmental risk factors associated with NAS.
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    Trends in Depressed Mood and Suicidal Behaviors Among Female High School Students Who Engaged in Physical Fighting
    (Sage, 2019) Ford, Janet H.; Zollinger, Terrell W.; Zhang, Jianjun; O'Neil, Joseph; Nelson, David R.; Steele, Gregory K.; Epidemiology, School of Public Health
    The objective of this article is to identify prevalence changes in depressed mood/suicidal behaviors among female high school students reporting physical fighting. This research analyzed the national combined data set of the Youth Risk Behavior Surveillance (YRBS) cross-sectional surveys from 2001 to 2015. Logistic regression analyzed the time trends. Two multiple logistic regression models were built. A quadratic trend was present with an initial decrease followed by an increase 2009 to 2015 (p < .001). The odds and severity of depressed mood/suicidal behaviors were greater among female youths with four or more fights and for other violent events, which were even greater when accounting for electronic bullying. The odds of depressed mood/suicidal behaviors among female adolescents engaged in physical fighting has been increasing with electronic bullying contributing to polyvictimization.