Research

Below is some information about different research projects I’ve worked on. An * indicates a project that I contributed to as a non-authored statistician.

WHO Functioning and Disability Disaggregation (FDD11) tool: a reliable approach for disaggregating data by disability

World Health Organization, Geneva, Switzerland

Citation: LEE, Lindsay et al. (2022), WHO Functioning and Disability Disaggregation (FDD11) tool: a reliable approach for disaggregating data by disability, Archives of Public Health 80(249), doi: 10.1186/s13690-022-01001-2

Abstract

Background: There is a global scarcity of good quality disability data, which has contributed to a lack of political will to address the challenges that persons with disabilities face. The current paper proposes a way forward to overcome this gap by demonstrating the psychometric properties of the World Health Organization Functioning and Disability Disaggregation Tool (FDD11) - a brief disability disaggregation instrument that countries can use. Results: The study demonstrated that FDD11 is a valid and reliable tool. Unidimensionality of the scale produced by each calibration was supported by the factor analysis performed. The analysis indicated good fit of the items, and targeting of the items was deemed to be sufficient. The person separation index was 0.82, indicating good reliability of the final scale. Conclusion: FDD11 provides a good opportunity to researchers and governments to capture good quality disability data and to disaggregate existing data by disability. The tool can facilitate low- and middle-income countries in their efforts to develop evidenced-based policies to address any barriers faced by persons with disabilities, to monitor the implementation of the Convention on the Rights of Persons with Disabilities and the Sustainable Development Goals, and to take stock of the challenges that still remain.

Demographic and environmental factors associated with disability in India, Laos, and Tajikistan: a population-based cross-sectional study

World Health Organization, Geneva, Switzerland

Citation: Chen, Michael Zhu et al. (2022), Demographic and environmental factors associated with disability in India, Laos, and Tajikistan: a population-based cross-sectional study, BMC Public Health, 22(607). doi: 10.1186/s12889-022-12846-1

Abstract

Background: The number of people experiencing functional limitations due to health conditions (capacity) is expected to increase in low and middle-income countries as populations age and rates of non-communicable disease rise. This trend could raise the prevalence and levels of disability worldwide. Understanding the demographic and environmental factors associated with disability can inform the design of policy interventions to make societies more accessible and inclusive for all. Methods: Approximately 2,500–3,000 participants in each of India, Laos, and Tajikistan responded to the Gallup World Poll and the World Health Organization’s Brief Model Disability Survey through face-to-face interviews. For each country, random forest regression was performed to explore the associations of demographic and environmental factors with disability while controlling for capacity. Using the variable importance measures generated by the random forest models, linear regression models were built in a stepwise manner for each country to predict disability level based on these contextual factors. Results: Capacity was strongly associated with disability in all three countries. Most of the variance in disability was explained by minimally adjusted linear models that included only capacity, sex, and age. Inclusion of additional demographic factors and environmental factors explained slightly more of the variance in disability score. Across all three countries, the level of basic infrastructure, public services, and financial stability were moderately associated with disability. Age, sex, employment status, the use of assistive technologies, and other factors had associations with disability that were highly variable across countries. Conclusion: While capacity was the main determinant of disability, individual demographic and environmental factors were associated with disability in a country-specific manner while controlling for the effects of capacity.

Generating comprehensive functioning and disability data worldwide: development process, data analyses strategy and reliability of the WHO and World Bank Model Disability Survey

World Health Organization, Geneva, Switzerland

Citation: Sabariego, Carla et al. (2022), Generating comprehensive functioning and disability data worldwide: development process, data analyses strategy and reliability of the WHO and World Bank Model Disability Survey, Archives of Public Health, 80(6). doi: 10.1186/s13690-021-00769-z

Abstract

Background: Data on functioning and disability collected at population level is essential to complement mortality and morbidity, to estimate rehabilitation needs of countries and regions and to monitor the Convention on the Rights of Persons with Disabilities (CRPD) and the Sustainable Development Goals (SDGs). The objective of this paper is to briefly report the development process of the WHO Model Disability Survey, its data analysis strategy as well as its reliability and ability to measure low to high levels of functioning and disability across countries. Methods: The development process is described in detail, and a secondary analysis using Rasch methods is conducted to report reliability and targeting using data from eight national and two regional implementations of the survey. Results: The currently available versions of the Model Disability Survey are presented. The survey has good to very good internal reliability and good targeting in all included countries. Conclusion: The participatory and evidence-based development, consideration of the expertise of stakeholders, the availability of previously developed ICF-based surveys, and WHO tools targeting functioning and disability are reflected in its good to very good psychometric properties. The survey has been implemented to date in Afghanistan, Cameroon, Chile, Costa Rica, India, Laos, Pakistan, Philippines, Sri Lanka, and Tajikistan, and is used to inform policy-making, to monitor the CRPD and SDGs and to plan the delivery of rehabilitation services.

Measuring functioning and disability using household surveys: metric properties of the brief version of the WHO and World Bank model disability surveys

World Health Organization, Geneva, Switzerland

Citation: Sabariego, Carla et al. (2021), Measuring functioning and disability using household surveys: metric properties of the brief version of the WHO and World Bank model disability survey. Archives of Public Health, 79(1):128. doi: 10.1186/s13690-021-00654-9

Abstract

Background: The Model Disability Survey (MDS) is the current standard recommended by WHO to collect functioning and disability data. Answering calls from countries requesting a version to be implemented as a module that could be integrated into existing surveys and be used for monitoring disability trends and for data disaggregation, WHO developed the brief MDS. The objectives of this paper are to evaluate the metric properties of the disability metrics generated with the Brief MDS and the precision of the Brief MDS in comparison with the full MDS. Results: The partial credit model, a unidimensional model for polytomous data from the Rasch family, was applied to evaluate psychometric properties using data from national MDS implementations in Chile (N = 12,265) and in Sri Lanka (N = 3000). The Brief MDS generates valid metrics for measuring disability, from the perspectives of capacity and performance, thereby achieving good levels of measurement precision in comparison with its full counterpart. Conclusion: Given the scarcity of valid functioning and disability modules for household surveys, the Brief MDS represents a milestone in disability measurement. The Brief MDS is currently used by countries to monitor disability trends over time, which is especially important to evaluate the impact of health policies and public health interventions, to disaggregate indicators of the Sustainable Development Goals, and to monitor the implementation of the UN Convention on the Rights of Persons with Disabilities (CRPD).

Identifying key environmental barriers experienced by persons with mild, moderate, or severe disability in Bankim Health District, Cameroon: a policy-targeted secondary analysis of data obtained with the World Bank and WHO model disability survey

World Health Organization, Geneva, Switzerland

Citation: Lee, Lindsay et al. (2021), Identifying key environmental barriers experienced by persons with mild, moderate, or severe disability in Bankim Health District, Cameroon: a policy-targeted secondary analysis of data obtained with the World Bank and WHO model disability survey. Archives of Public Health, 79(95). doi: 10.1186/s13690-021-00619-y

Abstract

Background: Comprehensive data is key for evidence-informed policy aiming to improve the lives of persons experiencing different levels of disability. The objective of this paper was to identify the environmental barriers — including physical, social, attitudinal, and political barriers — that might become priorities for cross-cutting policies and policies tailored to the needs of persons experiencing severe disability in Cameroon. Methods: A secondary analysis of data obtained with the WHO Model Disability Survey was completed in the Bankim Health District (N = 559) using random forest regression to determine and compare the impact of the environmental factors on the experience of disability. Results: The physical environment had by far the highest influence on disability, with transportation, toilet of the dwelling, and the dwelling itself being the most important factors. Factors inside one’s own home (toilet of the dwelling, and the dwelling itself) were the most important for persons with moderate and severe disability, followed by attitudes of others and issues with accessing health care. Conclusion: Our study provides country policy makers with evidence for setting priorities and for the development of evidence-informed policies for the Bankim Health District in Cameroon.

Response to “Commentary on: The First Global Physical Activity and Sedentary Behavior Guidelines for People Living With Disability”

World Health Organization, Geneva, Switzerland

Citation: Carty, Catherine et al. (2021), Response to “Commentary on: The First Global Physical Activity and Sedentary Behavior Guidelines for People Living With Disability”. Journal of Physical Activity and Health. doi: 10.1123/jpah.2021-0137

Measurement of violence against women and disability: protocol for a scoping review

World Health Organization, Geneva, Switzerland

Citation: Meyer, Sarah et al. (2020), Measurement of violence against women and disability: protocol for a scoping review. BMJ Open. doi: 10.1136/bmjopen-2020-040104

Abstract

Introduction: Violence against women is a serious threat to women’s health and human rights globally. Disability has been associated with increased risk of exposure to different forms of violence, however, there are questions concerning how best to measure this association. Research on understanding the association between violence and disability among women has included incorporating short disability measures into violence against women prevalence surveys. The potential to improve understanding of interconnections between violence and disability by measuring violence within disability-focused research is underexplored. The scoping review described here focuses on three areas of measurement of violence against women and disability: (1) measurement of violence within the context of disability-focused research, (2) measurement in research focused on the intersection of disability and violence and (3) measurement of disability in the context of research focused on violence against women. Specifically, we aim to map definitions, measures and methodologies in these areas, globally. Methods and analysis: For our scoping review, we will conduct searches for quantitative studies of disability-focused research which use measures of violence against women, and measures of disability in research focused on violence against women, in 11 online databases. Two authors will independently review titles and abstracts retrieved through the search strategy. We will search for grey literature, search the websites of National Statistics Offices for all countries to identify any national or subnational disability research and consult with experts for input. Data extraction will be conducted independently by one author and reviewed by another author, and data will be analysed and synthesised using a thematic synthesis approach.

The First Global Physical Activity and Sedentary Behavior Guidelines for People Living With Disability

World Health Organization, Geneva, Switzerland

Citation: Carty, Catherine et al. (2020), The First Global Physical Activity and Sedentary Behavior Guidelines for People Living With Disability. Journal of Physical Activity and Health. doi: 10.1123/jpah.2020-0629

Abstract

Background: The World Health Organization has released the first global public health guidelines on physical activity and sedentary behavior for people living with disability. This paper presents the guidelines, related processes, and evidence, and elaborates upon how the guidelines can support inclusive policy, practice, and research. Methods: Methods were consistent with the World Health Organization protocols for developing guidelines. Systematic reviews of the evidence on physical activity for health for people living with disability were appraised, along with a consideration of the evidence used to inform the general 2020 World Health Organization guidelines. Results: Evidence supported the development of recommendations for people living with disability, stressing that there are no major risks to engaging in physical activity appropriate to an individual’s current activity level, health status, and physical function, and that the health benefits accrued generally outweigh the risks. They also emphasize the benefits of limiting sedentary behavior. Conclusions: The guidelines mark a positive step forward for disability inclusion, but considerable effort is needed to advance the agenda. This paper highlights key considerations for the implementation of the new recommendations for people living with disability, in line with the human rights agenda underpinning the Global Action Plan on Physical Activity 2018–2030 and allied policies.

Model disability survey: a pilot study in the North Batinah governorate

World Health Organization, Geneva, Switzerland

Authors: Adhra Al-Mawali, Magdi Morsi, Hilal Al-Kharusi, Waleed Al-Shekaili, Carla Sabariego, and Lindsay Lee

Citation: Al-Mawali, Adhra et al. (2018), Model disability survey: a pilot study in the North Batinah governorate. Journal of Contemporary Medical Sciences, 4(4): 191-194. ISSN 2413-0516. doi: 10.22317/jcms.v4i4.489

Abstract

The continuous shift to non-communicable diseases in Oman require a more consistent inclusion of functioning and disability information in health monitoring and evaluation frameworks. Oman currently relies on the census to generate data on disability which is usually very limited in scope, and provides only rough prevalence estimates of persons with specific impairments. The lack of accurate, comprehensive and up-to-date information on disability is a major obstacle for planning services and allocating resources. Thus, there was a need to conduct a comprehensive population-based survey to fill this information gap. The pilot aimed to examine the feasibility of the Arabic version of the Model Disability Survey (MDS) in the cultural context of Oman, identify potential problems with the survey, and develop strategies to deal with them before a large national implementation is launched. The MDS is the tool recommended by the World Health Organization(WHO) to collect comprehensive data about functioning and disability to quantify both the impact of health conditions or impairments as well as the impact of the environment on disability. To determine the applicability of measuring disability, a pilot study was carried out in the North Batinah governorate of Oman with a convenience sample of 288 adults aged 18 year or older in collaboration with WHO. The overall disability prevalence was estimated to be 14.6% (n = 42) in the MDS pilot study calculated by determining the proportion of people in the population who experience severe performance problems. The overall results corroborated that the Arabic translation of the MDS survey tool works well in the field and is suitable for a large scale implementation, after minor revisions. Since the results of this pilot study in Oman show that the disability measurement survey tool has been successfully tested, we recommend that the MDS be extended and implemented nationally. It should also be integrated to existing routine household surveys to allow continuous monitoring of disability in countries.

An Empirical Study of Punitive Damages*

University of Oxford, United Kingdom

Authors: James Goudkamp and Eleni Katsampouka

Citation: Goudkamp, J. and Katsampouka, E. (2017), An Empirical Study of Punitive Damages. Oxford Journal of Legal Studies: 1-33. doi: 10.1093/ojls/gqx013

Abstract

This article reports and discusses the results of an empirical study of punitive damages. It examines 146 claims that were decided in all parts of the UK (save for Scotland, which does not recognise punitive damages) by first instance courts in the first 16years of the twenty-first century. The study is the first of its kind to be conducted in the UK. In the morass of data, important evidence is uncovered regarding punitive damages. Our most significant findings include (1) that punitive damages (when claimed) are awarded reasonably regularly, (2) that the average award of punitive damages is relatively modest, (3) that there is considerable uniformity in terms of the size of punitive damages awards, and (4) that actions for defamation are unlikely to constitute an important source of punitive damages awards. These (and other) findings cast considerable doubt upon widely held views regarding punitive damages.

Contributory Negligence in the Twenty-First Century: An Empirical Study of First Instance Decisions*

University of Oxford, United Kingdom

Authors: James Goudkamp and Donal Nolan (Faculty of Law)

Citation: Goudkamp, J. and Nolan, D. (2016), Contributory Negligence in the Twenty-First Century: An Empirical Study of First Instance Decisions. The Modern Law Review, 79: 575–622. doi: 10.1111/1468-2230.12202

Abstract

In this article we report the results of an empirical study of 368 first instance decisions on the contributory negligence doctrine handed down in England and Wales between 2000 and 2014. The two central questions at which we looked were: how often a defendant’s plea of contributory negligence was successful; and by how much a claimant’s damages were reduced when a finding of contributory negligence was made. We also considered the extent to which the answers to these questions depended on the following variables: the claimant’s age; the claimant’s gender; the type of damage suffered by the claimant; the contextual setting of the claim; and the year of the decision. Our study uncovered several important truths about the contributory negligence doctrine hidden in this mass of case law, some of which cast significant doubt on the accuracy of widely held views about the doctrine’s operation.

Dynamic time warping for assessment of inter-rater reliability for annotations of wearable camera data

University of Oxford, United Kingdom

Mentor: Órlaith Burke (Nuffield Department of Population Health)

Abstract

Wearable cameras are increasingly being used in research as a means to gather more robust information about people’s daily activity levels. However, the quantity and complexity of the data produced by these cameras requires the development of an image annotation scheme that is sufficiently descriptive yet able to be implemented consistently by multiple researchers. In order to analyze the ability of the image annotation protocol to produce consistent annotations, inter-rater reliability (IRR) needs to be assessed. Traditional methods of assessing IRR like Cohen’s kappa do not utilize the unique features of the image annotation data, so a new method is needed.

In this report we implement a dynamic time warping (DTW) algorithm with the longest common prefix (LCP) distance metric to assess IRR for annotations of images produced by wearable cameras. Two raters each produced image annotations for twelve study participants. We use DTW with four different step patterns to align the two time series and calculate the normalized distance for each warping path. This normalized distance is used as the new metric of inter-rater reliability. We also implement DTW for randomly simulated annotations in order to provide a baseline normalized distance to compare against the normalized distances for our observed data. We conclude that DTW with the LCP distance metric and Rabiner-Juang type 5 step pattern is the most appropriate method to analyze IRR for this type of data. It represents an improvement upon traditional measures of IRR because it utilizes the time series characteristics of the data and the hierarchical nature of the categories in the image annotation protocol.

Modeling feral cat dynamics in Knox County, TN

National Institute of Mathematical and Biological Synthesis, Knoxville, TN

Mentors: Suzanne Lenhart, John C. New (University of Tennessee)

Additional co-authors: Nick Robl, Alice M. Bugman, An T.N. Nguyen, Bridgid Lammers, Teresa L. Fisher, Heidi Weimer

Abstract

Feral cats (Felis catus) are recognized as a problem internationally due to their negative impact on wildlife and potential to spread infectious disease to people and other animals. Trap-neuter-return (TNR) programs are employed in many areas to control feral cat populations as a humane method, and this approach is used on a limited basis in Knox County, Tennessee. Despite the frequent use of TNR as a strategy, its effectiveness remains controversial. The objective of this mathematical model is to predict the impact of selected strategies on the population of feral cats. The model with three age classes predicts the population over a period of 5 years in one month time steps. TNR rates are varied to investigate the effects of targeting spay/neuter programs seasonally, and such targeting predicts a measurable decline in feral cat population growth over a five year period. Targeting TNR intervention at adult females during the time prior to mating season in highly populated feral colonies may further decrease the population. These results suggest a more efficacious strategy than non-targeted TNR programs.

Event detection using natural language processing

Vanderbilt University Medical Center, Nashville, TN

Mentors: Jesse Ehrenfeld, Paul St. Jacques (VUMC)

Abstract

Integrated into every patient’s chart are check lists that anesthesiologists use to indicate specific events within a surgery, including adverse events. Studies show that in anesthesiology 27% of cases have a non-routine event, but voluntary reporting of such events is low (Weigner et al. 2003). Voluntary incident reporting only detects 1.5% of adverse events and only 6% of adverse drug events (Murff 2003). Anesthesiologists also have fields where they can enter free text on a patient’s chart post-operatively. We hypothesize that we will be able to detect a greater number of adverse events through the use of natural language processing tools in Python that search for specific key phrases and language structures that indicate a certain event has occurred. We aim to discover the real rate of occurrence for a specific adverse event in anesthesiology at Vanderbilt University and to calculate the effectiveness of the checklist. We began this research looking for instances of difficult intubation. We analyzed the comment fields of patient charts at Vanderbilt University retrospectively for two sample weeks in June 2012, totally approximately 5500 case comments. With a sample size of 1800 comments, the Python program finds all the comments discussing difficult intubation. There are 18 total comments in this sample size with difficult intubation. With more sample points, the program misses some comments and outputs some comments that do not include difficult intubation. Our original hypothesis about underreporting of difficult intubation is correct by our analysis. Though the NLP program needs improvements to be accurate for larger sizes of data, the majority of the cases that mentioned difficult intubation in the case comments did not have an explicit reporting of it in the structured checkboxes. Despite 88.9% of these cases explicitly reporting multiple attempts at intubation, only 16.7% were listed as “difficult,” and 44.4% were listed as “easy.” The information from this report could be used to implement a system for the operating room that reminds medical personnel to report difficult intubations in the checkboxes.

Fitting the eigensolution of compartment models

Oak Ridge National Laboratory, Oak Ridge, TN

Mentors: Richard C. Ward, Keith F. Eckerman (ORNL)

Abstract

The radiation dosimetry community uses models to describe the fate of inhaled or ingested radionuclides. Such exposures can result in cell death and cell transformations that depend strongly on the behavior of the radionuclide within the body. In some instances medical attention requires that such analyses can be quickly performed. An example of such software is Integrated Modules for Bioassay (IMBA), developed by the United Kingdom to interpret urine and fecal bioassay samples. The software lacks a differential equation solver and instead uses a function to fit solutions to the equations. Eigenanalysis software produced by Killough and Eckerman can be used to find the exact solution, but solutions often include ten or more exponential terms in linear combination. The IMBA software can only handle up to ten terms, so those solutions with more terms must be reduced for use in IMBA. The purpose of this research is to develop a method to solve compartment models describing physiological and chemical processes and to fit the numerical solution by sums of exponential terms of a reduced number. This will enable the use of the models to be computed faster than the original approach. The exact solution of a plutonium biokinetic compartment model will be reduced to determine the optimum functional fit for the IMBA program. The exact solution contains up to eighteen terms. The ten-term solution set will fit the exact solution curves as nearly as possible. The solution set will be determined by an automated non-linear curve-fitting algorithm in Mathematica. It was found that Mathematica provides a simpler data fitting method than the trial and error method previously used, but many problems were encountered. The difficulty in determining what fitting method is being used leads to bad fits that have yet to be explained. Also, the time to run the fitting algorithm on some compartments is too long to be efficient. These problems may make the program not ideal for its original purpose.

Patterns at the smallest scale: fractal analysis of the lung and modeling of nanoparticle clearance

Oak Ridge National Laboratory, Oak Ridge, TN

Mentor: Richard C. Ward (ORNL)

Abstract

This paper explores the accuracy of a fractal-based model for the airway system of the human lung and the clearance of nanoparticles within the system. The purpose of research is to create realistic lung models based on fractals and inhalation kinetics so nanoparticle deposition and clearance can be visualized and understood. Lung diameter data is analyzed using rules for surface area maximization of previous lung branching models. The diameter data is then displayed on a model of a lung branching tree based on the Lindenmayer system method of producing fractals. The clearance model of particles derived by the International Commission on Radiological Protection is created in compartment form in the program JDesigner from Systems Biology Workbench, and then analyzed for its possible application toward modeling particles on the nano-scale. The research has the potential to aid in the development of nanoparticle drug delivery systems through inhalation. These systems could target diseases as a result of regional deposition modeling and nanoparticles’ natural ability to diffuse through a variety of membranes.s