Papers by Georgiy Bobashev
Objective. In this methodological paper, we use a novel, predictive approach to examine how demog... more Objective. In this methodological paper, we use a novel, predictive approach to examine how demographics, substance use, mental and other health indicators predict multiple visits (≥3) to emergency departments (ED) within a year. Methods. State-of-the-art predictive methods were used to evaluate predictive ability and factors predicting multiple visits to ED within a year and to identify factors that influenced the strength of the prediction. The analysis used public-use datasets from the 2015-2018 National Surveys on Drug Use and Health (NSDUH), which used the same questionnaire on the variables of interest. Analysis focused on adults aged ≥18 years. Several predictive models (regressions, trees, and random forests) were validated and compared on independent datasets. Predictive ability on a test set for multiple ED visits (≥3 times within a year) measured as the area under the receiver operating characteristic (ROC) was 0.79, which is good for a national survey. Models revealed consistency in predictive factors across the 4 survey years. The most influential variables for predicting ≥3 ED visits per year were fair/poor self-rated health, having a lower income, asthma, heart condition/disease, having chronic obstructive pulmonary disease (COPD), African-American race, female sex, having diabetes, being restless/fidgety, and being of younger age (18-25). The findings reveal the need to address behavioral and mental health contributors to ED visits and reinforce the importance of developing integrated care models in primary care settings to improve mental health for medically vulnerable patients. Presented modeling approach can be broadly applied to national and other large surveys. * Marital status was changed to ACASI in 2015 then, because of data quality issues, was moved back to CAPI in 2016-2018. Education also was administered with ACASI.
BMC Medical Research Methodology, Dec 1, 2017
Background: Summary of findings tables in systematic reviews are highly informative but require e... more Background: Summary of findings tables in systematic reviews are highly informative but require epidemiological training to be interpreted correctly. The usage of fishbone diagrams as graphical displays could offer researchers an effective approach to simplify content for readers with limited epidemiological training. In this paper we demonstrate how fishbone diagrams can be applied to systematic reviews and present the results of an initial user testing. Methods: Findings from two systematic reviews were graphically depicted in the form of the fishbone diagram. To test the utility of fishbone diagrams compared with summary of findings tables, we developed and pilot-tested an online survey using Qualtrics. Respondents were randomized to the fishbone diagram or a summary of findings table presenting the same body of evidence. They answered questions in both open-ended and closed-answer formats; all responses were anonymous. Measures of interest focused on first and second impressions, the ability to find and interpret critical information, as well as user experience with both displays. We asked respondents about the perceived utility of fishbone diagrams compared to summary of findings tables. We analyzed quantitative data by conducting ttests and comparing descriptive statistics. Results: Based on real world systematic reviews, we provide two different fishbone diagrams to show how they might be used to display complex information in a clear and succinct manner. User testing on 77 students with basic epidemiological training revealed that participants preferred summary of findings tables over fishbone diagrams. Significantly more participants liked the summary of findings table than the fishbone diagram (71.8% vs. 44.8%; p < .01); significantly more participants found the fishbone diagram confusing (63.2% vs. 35.9%, p < .05) or indicated that it was difficult to find information (65.8% vs. 45%; p < .01). However, more than half of the participants in both groups were unable to find critical information and answer three respective questions correctly (52.6% in the fishbone group; 51.3% in the summary of findings group). Conclusions: Fishbone diagrams are compact visualizations that, theoretically, may prove useful for summarizing the findings of systematic reviews. Initial user testing, however, did not support the utility of such graphical displays.
Modeling the impact of thermal effects on luminous flux maintenance for SSL luminaires
2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)
Meeting the longevity requirements of solid-state lighting (SSL) devices places extreme demands o... more Meeting the longevity requirements of solid-state lighting (SSL) devices places extreme demands on the materials and designs that are used in SSL luminaires. Therefore, understanding the aging characteristics of lens, reflectors, and other materials is essential to projecting the long-term performance of LED-based lighting systems. Overlooking these factors at either the design or product specification stage can result in premature failure of the device due to poor luminous flux maintenance and/or excessive chromaticity shifts. This paper describes a methodology for performing accelerated stress testing (AST) on materials intended for use in SSL luminaires. This test methodology, which consists of elevated temperature and humidity conditions, produces accelerated aging data that can be correlated to expected performance under normal luminaire operating conditions. The correlations can then be leveraged to produce models of the changes in the optical properties of key materials including transmittance versus wavelength of lenses and reflectance versus wavelength for housings and other reflectors. This information has been collected into a lumen maintenance decision support tool (LM-DST) and together with user supplied inputs (e.g., expected operation conditions) can provide guidance on lifetime expectations of SSL luminaires. This approach has been applied to a variety of materials commonly found in SSL luminaires including acrylics, polycarbonates, and silicones used for lenses and paints, coatings, films, and composites used for reflectors.
Alcohol and Alcoholism, 2021
Aims We tested the hypothesis that high novelty seeking (NS—an externalizing trait), sweet-liking... more Aims We tested the hypothesis that high novelty seeking (NS—an externalizing trait), sweet-liking (SL—a phenotype that may reflect processing of hedonic stimuli) and initial insensitivity to the impairing effects of alcohol (SRE-A) act independently and synergistically to increase the likelihood of having alcohol-related problems in young adults. Methods A sample of 145 young adults, ages 18–26, balanced for gender and alcohol use disorders identification test (AUDIT) scores <8 or ≥8 were selected from a prior sample. NS, SL and SRE-A were assessed along with AUDIT score and family history of alcoholism (FH). The effect of phenotypes and their interaction on the likelihood of alcohol problems was assessed. Results All three phenotypes contribute to the total AUDIT score. The best-fitting model explaining 35.8% of AUDIT variance includes all three phenotypes and an interaction between NS and SL/sweet-disliking (SDL) status. The addition of FH to the model explains an additional 4%...
Additional file 1 of Predictive model of multiple emergency department visits among adults: analysis of the data from the National Survey of Drug Use and Health (NSDUH)
Additional file 1: Table A1. Sociodemographic characteristics, substance use behaviors, mental he... more Additional file 1: Table A1. Sociodemographic characteristics, substance use behaviors, mental health issues, and prevalence of ED visits in the past 12 months among adults in the national sample of the NSDUH.
Additional file 2: of User testing of an adaptation of fishbone diagrams to depict results of systematic reviews
Survey. Survey Word File (DOCX 29 kb)
Strength of Evidence Assessments
Journal of Computational Science, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Spatial Modeling of Influenza Outbreaks in Saint Petersburg Using Synthetic Populations
Lecture Notes in Computer Science, 2019
In this paper, we model influenza propagation in the Russian setting using a spatially explicit m... more In this paper, we model influenza propagation in the Russian setting using a spatially explicit model and a detailed human agent database as its input. The aim of the research is to assess the applicability of this modeling method using influenza incidence data for 2010–2011 epidemic outbreak in Saint Petersburg and to compare the simulation results with the output of the compartmental SEIR model for the same outbreak. For this purpose, a synthetic population of Saint Petersburg was built and used for the simulation via FRED open source modeling framework. The parameters related to the outbreak (background immunity level and effective contact rate) are assessed by calibrating the compartmental model to incidence data. We show that the current version of synthetic population allows the agent-based model to reproduce real disease incidence.
BMC medical research methodology, Jan 12, 2017
Summary of findings tables in systematic reviews are highly informative but require epidemiologic... more Summary of findings tables in systematic reviews are highly informative but require epidemiological training to be interpreted correctly. The usage of fishbone diagrams as graphical displays could offer researchers an effective approach to simplify content for readers with limited epidemiological training. In this paper we demonstrate how fishbone diagrams can be applied to systematic reviews and present the results of an initial user testing. Findings from two systematic reviews were graphically depicted in the form of the fishbone diagram. To test the utility of fishbone diagrams compared with summary of findings tables, we developed and pilot-tested an online survey using Qualtrics. Respondents were randomized to the fishbone diagram or a summary of findings table presenting the same body of evidence. They answered questions in both open-ended and closed-answer formats; all responses were anonymous. Measures of interest focused on first and second impressions, the ability to find...
System reliability for LED-based products
2014 15th International Conference on Thermal, Mechanical and Mulit-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2014
Results from accelerated life tests (ALT) on mass-produced commercially available 6" downlig... more Results from accelerated life tests (ALT) on mass-produced commercially available 6" downlights are reported along with results from commercial LEDs. The luminaires capture many of the design features found in modern luminaires. In general, a systems perspective is required to understand the reliability of these devices since LED failure is rare. In contrast, components such as drivers, lenses, and reflector are more likely to impact luminaire reliability than LEDs.
Insights into accelerated aging of SSL luminaires
SPIE Proceedings, 2013
Although solid-state lighting (SSL) products are often intended to have product lifetimes of 15 y... more Although solid-state lighting (SSL) products are often intended to have product lifetimes of 15 years or more, the rapid change in technology has created a need for accelerated life tests (ALTs) that can be performed in the span of several months. A critical element of interpreting results from any systems-level ALT is understanding of the impact of the test environment on each component. Because of its ubiquity in electronics, the use of temperature-humidity environments as potential ALTs for SSL luminaires was investigated. Results from testing of populations of three commercial 6” downlights in environments of 85°C and 85% relative humidity (RH) and 75°C and 75% RH are reported. These test environments were found to accelerate lumen depreciation of the entire luminaire optical system, including LEDs, lenses, and reflectors. The effects of aging were found to depend strongly on both the optical materials that were used and the design of the luminaire; this shows that the lumen maintenance behavior of SSL luminaires must be addressed at the optical systems level. Temperature-Humidity ALTs can be a useful test in understand lumainaire depreciation provided that proper consideration is given to the different aging rates of various materials. Since the impact of the temperature-humidity environment varies among components of the optical system, uniform aging of all system components in a single test is difficult to achieve.
Drug and Alcohol Dependence, 2007
The science of mathematical modeling aims to describe and evaluate complex phenomena. In epidemio... more The science of mathematical modeling aims to describe and evaluate complex phenomena. In epidemiology, modeling allows scientists to simulate the consequences of various intervention and prevention scenarios. In biology, modeling allows one to describe and simulate complex neurophysiologic processes. Similar modeling techniques apply to both scenarios. At the 2006 College on Problems of Drug Dependence (CPDD) workshop, we presented four types of models: traditional epidemiologic, traditional neurobiological/behavioral, knowledge repository epidemiologic, and knowledge repository neurobiological/behavioral. We discussed commonality and differences in the approaches, interpretations, utility, and limitations. The authors believe that both traditional and knowledge repository models can be very useful in complementary ways to the general scientific community studying substance abuse.
This publication is part of the RTI Press Research Report series. Occasional Papers are scholarly... more This publication is part of the RTI Press Research Report series. Occasional Papers are scholarly essays on policy, methods, or other topics relevant to RTI areas of research or technical focus..
Objective: Dichotomizing clinical trials designs into nomothetic (e.g., randomized clinical trial... more Objective: Dichotomizing clinical trials designs into nomothetic (e.g., randomized clinical trials or RCTs) versus idiographic (e.g., N-of-1 or case studies) precludes use of an array of hybrid designs and potential research questions between these extremes. This paper describes unique clinical evidence that can be garnered using idiographic clinical trials (ICTs) to complement RCT data. Proposed and illustrated herein is that innovative combinations of design features from RCTs and ICTs could provide clinicians with far more comprehensive information for testing treatments, conducting pragmatic trials, and making evidence-based clinical decisions. Method: Mixed model trajectory analysis and unified structural equations modeling were coupled with multiple baseline designs in (a) a true N-of-1 pilot study to improve severe autism-related communication deficits and (b) a small sample preliminary study of two complimentary interventions to relieve wheelchair discomfort. Results: Evidence supported certain mechanisms of treatment outcomes and ruled out others. Effect sizes included mean phase differences (i.e., effectiveness), trajectory slopes, and differences in path coefficients between study phases. Conclusions: ICTs can be analyzed with equivalent rigor as, and generate effect sizes comparable to, RCTs for the purpose of developing hybrid designs to augment RCTs for pilot testing innovative treatment, efficacy research on rare diseases or other small populations, quantifying within-person processes, and conducting clinical trials in many situations when RCTs are not feasible.
Infection Control and Hospital Epidemiology, Oct 1, 2020
Journal of Innovation and Entrepreneurship, Mar 7, 2018
Peer effects in innovation adoption decisions have been extensively studied. However, the underly... more Peer effects in innovation adoption decisions have been extensively studied. However, the underlying mechanisms of peer effects are generally not explicitly accounted for. Gaps in this knowledge could lead to misestimation of peer effects and inefficient interventions. This study examined the role of two mechanisms-sharing experiences (namely, experience effect) and externalities-in the adoption of an agricultural innovation. By referring to the diffusion process of a new crop in Chinese villages, we developed a simulation model that incorporated experience effect and externality effect on a multiplex network. The model allowed us to estimate the influence of each specific effect and to investigate the interplay of the positive and negative directions of the effects. The main results of simulation experiments were the following: (1) a negative externality effect in the system caused the diffusion of innovation to vary around a middle-level rate, which resulted in a fluctuating diffusion curve rather than a commonly found S-shaped one; (2) in the case of full diffusion, experience effect significantly shaped the diffusion process at the early stage, while externality effect mattered more at the late stage; and (3) network properties (i.e. connectivity, transitivity, and network distance) imposed indirect influence on diffusion through specific peer effects. Overall, our study illustrated the need to understand specific causal mechanisms when studying peer effects. Simulation methods such as agent-based modelling provide an effective approach to facilitate such understanding.
Carolina Digital Repository (University of North Carolina at Chapel Hill), 2013
There is a need for brief HIV prevention interventions that can be disseminated and implemented w... more There is a need for brief HIV prevention interventions that can be disseminated and implemented widely. This article reports the results of a small randomized field experiment that compared the relative effects of a brief 2-session counselor-delivered computer-tailored intervention and a control condition. The intervention is designed for use with African American, non-Hispanic white and Hispanic males and females who may be at risk of HIV through unprotected sex, selling sex, male to male sex, injecting drug use or use of stimulants. Participants (n=120) were recruited using a quota sampling approach and randomized using block randomization, which resulted in 10 male and 10 female participants of each racial/ethnic group (i.e. African-American, non-Hispanic white and Hispanic) being assigned to either the intervention or a control arm. In logistic regression analyses using a generalized estimating equations approach, at 3-month followup, participants in the intervention arm were more likely than participants in the control arm to report condom use at last sex (Odds ratio [OR] = 4.75; 95% Confidence interval [C.I.] = 1.70, 13.26; p = 0.003). The findings suggest that a brief tailored intervention may increase condom use. Larger studies with longer followups are needed to determine if these results can be replicated.
Pediatrics, 2011
Bronchopulmonary dysplasia is a major cause of morbidity in premature infants. Outcomes of most n... more Bronchopulmonary dysplasia is a major cause of morbidity in premature infants. Outcomes of most neonatal disorders, including bronchopulmonary dysplasia, vary in incidence across neonatal centers even after adjustment for demographic and antenatal characteristics. The factors responsible for such variation have not been systematically evaluated. WHAT THIS STUDY ADDS: Bronchopulmonary dysplasia/death rates were found to demonstrate a moderate clustering effect according to center, as did clinical variables associated with the outcome. Persistent center differences after clustered variables were corrected indicated the presence of as-yet unmeasured center variables.
JMIR formative research, Mar 30, 2022
The cessation of opioid use can cause withdrawal symptoms. People often continue opioid misuse to... more The cessation of opioid use can cause withdrawal symptoms. People often continue opioid misuse to avoid these symptoms. Many people who use opioids self-treat withdrawal symptoms with a range of substances. Little is known about the substances that people use or their effects. The aim of this study is to validate a methodology for identifying the substances used to treat symptoms of opioid withdrawal by a community of people who use opioids on the social media site Reddit. We developed a named entity recognition model to extract substances and effects from nearly 4 million comments from the r/opiates and r/OpiatesRecovery subreddits. To identify effects that are symptoms of opioid withdrawal and substances that are potential remedies for these symptoms, we deduplicated substances and effects by using clustering and manual review, then built a network of substance and effect co-occurrence. For each of the 16 effects identified as symptoms of opioid withdrawal in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, we identified the 10 most strongly associated substances. We classified these pairs as follows: substance is a Food and Drug Administration-approved or commonly used treatment for the symptom, substance is not often used to treat the symptom but could be potentially useful given its pharmacological profile, substance is a home or natural remedy for the symptom, substance can cause the symptom, or other or unclear. We developed the Withdrawal Remedy Explorer application to facilitate the further exploration of the data. Our named entity recognition model achieved F 1 scores of 92.1 (substances) and 81.7 (effects) on hold-out data. We identified 458 unique substances and 235 unique effects. Of the 130 potential remedies strongly associated with withdrawal symptoms, 54 (41.5%) were Food and Drug Administration-approved or commonly used treatments for the symptom, 17 (13.1%) were not often used to treat the symptom but could be potentially useful given their pharmacological profile, 13 (10%) were natural or home remedies, 7 (5.4%) were causes of the symptom, and 39 (30%) were other or unclear. We identified both potentially promising remedies (eg, gabapentin for body aches) and potentially common but harmful remedies (eg, antihistamines for restless leg syndrome). Conclusions: Many of the withdrawal remedies discussed by Reddit users are either clinically proven or potentially useful. These results suggest that this methodology is a valid way to study the self-treatment behavior of a web-based community of people who use opioids. Our Withdrawal Remedy Explorer application provides a platform for using these data for pharmacovigilance, the identification of new treatments, and the better understanding of the needs of people undergoing opioid withdrawal. Furthermore, this approach could be applied to many other disease states for which people self-manage their symptoms and discuss their experiences on the web.
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Papers by Georgiy Bobashev