State-Space Models for Binomial Time Series with Excess Zeros

Count time series with excess zeros are frequently encountered in practice. In characterizing a time series of counts with excess zeros, two types of models are commonplace: models that assume a Poisson mixture distribution, and models that assume a binomial mixture distribution. Extensive work has been published dealing with modeling frameworks based on Poisson-type approaches, yet little has concentrated on binomial-type methods. To handle such data, we propose two general classes of time series models: a class of observation-driven ZIB (ODZIB) models, and a class of parameter-driven ZIB (PDZIB) models. The ODZIB model is formulated in the partial likelihood framework, which facilitates model fitting using standard statistical software for ZIB regression models. The PDZIB model is conveniently formulated in the state-space framework. For parameter estimation, we devise a Monte Carlo Expectation Maximization (MCEM) algorithm, with particle filtering and particle smoothing methods employed to approximate the intractable conditional expectations in the E-step of the algorithm. We investigate the efficacy of the proposed methodology in a simulation study, which compares the performance of the proposed ZIB models to their counterpart zero-inflated Poisson (ZIP) models in characterizing zero-inflated count time series. We also present a practical application pertaining to disease coding

National trends in total hip arthroplasty for traumatic hip fractures: An analysis of a nationwide all-payer database.

BACKGROUND: Hemiarthroplasty (HA) has traditionally been the treatment of choice for elderly patients with displaced femoral neck fractures. Ideal treatment for younger, ambulatory patients is not as clear. Total hip arthroplasty (THA) has been increasingly utilized in this population however the factors associated with undergoing HA or THA have not been fully elucidated. AIM: To examine what patient characteristics are associated with undergoing THA or HA. To determine if outcomes differ between the groups. METHODS: We queried the Nationwide Inpatient Sample (NIS) for patients that underwent HA or THA for a femoral neck fracture between 2005 and 2014. The NIS comprises a large representative sample of inpatient hospitalizations in the United States. International Classifications of Disease, Ninth Edition (ICD-9) codes were used to identify patients in our sample. Demographic variables, hospital characteristics, payer status, medical comorbidities and mortality rates were compared between the two procedures. Multivariate logistic regression analysis was then performed to identify independent risk factors of treatment utilized. RESULTS: Of the total 502060 patients who were treated for femoral neck fracture, 51568 (10.3%) underwent THA and the incidence of THA rose from 8.3% to 13.7%. Private insurance accounted for a higher percentage of THA than hemiarthroplasty. THA increased most in urban teaching hospitals relative to urban non-teaching hospitals. Mean length of stay (LOS) was longer for HA. The mean charges were less for HA, however charges decreased steadily for both groups. HA had a higher mortality rate, however, after adjusting for age and comorbidities HA was not an independent risk factor for mortality. Interestingly, private insurance was an independent predictor for treatment with THA. CONLUSION: There has been an increase in the use of THA for the treatment of femoral neck fractures in the United States, most notably in urban hospitals. HA and THA are decreasing in total charges and LOS

Charting the progression of disability in parkinson disease: study protocol for a prospective longitudinal cohort study

Journal ArticleBackground: People with Parkinson disease (PD), even in the presence of symptomatic relief from medical, surgical, and rehabilitative interventions, face a persistent worsening of disability. This disability is characterized by diminished quality of life, reduced functional mobility, declining performance in activities of daily living and worsening neurological impairments. While evidence has emerged supporting the clinically meaningful benefits of short-term exercise programs on these underlying factors, assertions regarding the effects of sustained programs of exercise and physical activity on the trajectory of disablement in PD are made in the absence of direct evidence. Indeed, the natural decline in quality of life and functional mobility in people diagnosed with PD is poorly understood. Moreover, outcome measures commonly used in clinical exercise trials typically do not capture the full spectrum of disability as defined by the World Health Organization (WHO). Methods/Design: The objective of this multicenter prospective study will be to examine the 2-year trajectory of disablement in a cohort of persons with PD. Two hundred sixty participants will be recruited to produce an expected final sample size of 150 individuals. Participants will be included if they are greater than 40 years of age, have a neurologist confirmed diagnosis of idiopathic PD, and are at Hoehn and Yahr stages 1 through 4. Data will be collected every 6 months during the study period. Primary outcome measures reflecting a broad spectrum of disablement will include, but will not be limited to, MDS-UPDRS, Timed Up and Go, Berg Balance Test, Nine Hole Peg Test, PDQ-39, and directly monitored ambulatory activity. Self-reported exercise and physical activity data also will be recorded. Statistical analyses will be used to characterize the trajectory of disablement and examine the influence of its underlying contributing factors. Discussion: Tertiary prevention is an important component of contemporary healthcare for individuals living with degenerative disease. For individuals with PD, there is growing recognition that exercise and/or physical activity efforts to slow the rate of functional mobility decline, in particular, may be critical for optimizing quality of life. By describing the natural trajectory of disablement, exercise habits, and physical activity in a cohort of persons with PD, this investigation will establish an important foundation for future intervention research. Specifically, through the evaluation of the influence of sustained exercise and physical activity on disablement, the study will serve as a preliminary step toward developing a randomized controlled trial of long-term exercise in persons with PD

A New Bootstrap Goodness-of-Fit Test for Normal Linear Regression Models

In this work, the distributional properties of the goodness-of-fit term in likelihood-based information criteria are explored. These properties are then leveraged to construct a novel goodness-of-fit test for normal linear regression models that relies on a non-parametric bootstrap. Several simulation studies are performed to investigate the properties and efficacy of the developed procedure, with these studies demonstrating that the bootstrap test offers distinct advantages as compared to other methods of assessing the goodness-of-fit of a normal linear regression model

Toward understanding ambulatory activity decline in Parkinson disease

BACKGROUND: Declining ambulatory activity represents an important facet of disablement in Parkinson disease (PD). OBJECTIVE: The primary study aim was to compare the 2-year trajectory of ambulatory activity decline with concurrently evolving facets of disability in a small cohort of people with PD. The secondary aim was to identify baseline variables associated with ambulatory activity at 1- and 2-year follow-up assessments. DESIGN: This was a prospective, longitudinal cohort study. METHODS: Seventeen people with PD (Hoehn and Yahr stages 1-3) were recruited from 2 outpatient settings. Ambulatory activity data were collected at baseline and at 1- and 2-year annual assessments. Motor, mood, balance, gait, upper extremity function, quality of life, self-efficacy, and levodopa equivalent daily dose data and data on activities of daily living also were collected. RESULTS: Participants displayed significant 1- and 2-year declines in the amount and intensity of ambulatory activity concurrently with increasing levodopa equivalent daily dose. Worsening motor symptoms and slowing of gait were apparent only after 2 years. Concurrent changes in the remaining clinical variables were not observed. Baseline ambulatory activity and physical performance variables had the strongest relationships with 1- and 2-year mean daily steps. LIMITATIONS: The sample was small and homogeneous. CONCLUSIONS: Future research that combines ambulatory activity monitoring with a broader and more balanced array of measures would further illuminate the dynamic interactions among evolving facets of disablement and help determine the extent to which sustained patterns of recommended daily physical activity might slow the rate of disablement in PD.This study was funded primarily by the Davis Phinney Foundation and the Parkinson Disease Foundation. Additional funding was provided by Boston University Building Interdisciplinary Research Careers in Women's Health (K12 HD043444), the National Institutes of Health (R01NS077959), the Utah Chapter of the American Parkinson Disease Association (APDA), the Greater St Louis Chapter of the APDA, and the APDA Center for Advanced PD Research at Washington University. (Davis Phinney Foundation; Parkinson Disease Foundation; K12 HD043444 - Boston University Building Interdisciplinary Research Careers in Women's Health; R01NS077959 - National Institutes of Health; Utah Chapter of the American Parkinson Disease Association (APDA); Greater St Louis Chapter of the APDA; APDA Center for Advanced PD Research at Washington University

Obituary: In Memory of Michael Jonathan Zigmond, Ph.D., September 1, 1941–August 28, 2023

Producción CientíficaNo abstract availabl

Rethinking What is Necessary in a Democratic Society: Militant Democracy and the Turkish State

Questions relating to contemporary understandings of democracy continue to preoccupy the academic landscape, from politics to law—how does one define democracy; is it necessary to recalibrate the concept of democracy to meet the exigencies of the current global security "crisis" and, following from this, how does one understand (and control) the democratic relationship of representation and accountability between citizen and state? Although those writing on the recalibration of democratic theory come from different points of departure, they often arrive at a similar conclusion; namely that this global era poses significant challenges to contemporary understandings of democracy. This article identifies and focuses on one challenge posed by the concept of “militant” democracy against the backdrop of the Turkish case

Animal Research for Alzheimer Disease: Failures of Science and Ethics

This chapter addresses the epidemiology and current understanding of AD as a scientific and societal challenge, reviews the uses and results of animal research in basic science and drug development, and discusses risk factors and funding. Important follow-up topics, including current and in-development, human-relevant approaches for replacement of the failed animal research paradigm, deserve comparable treatment and hence are not addressed here. The reader is referred to the list of recommended readings at the end of the chapter for further discussion of these topics

Gender-specific profiles of adverse childhood experiences, past year mental and substance use disorders, and their associations among a national sample of adults in the United States

Purpose: This study examined profiles of adverse childhood experiences (ACEs) and mental and substance use disorders (MSUDs), and associations between distinct profiles of ACEs and MSUDs. Methods: Participants were adults (N = 34, 652) involved in the National Epidemiologic Survey on Alcohol and Related Conditions. Latent class analysis was used to examine both profiles of ten ACEs and ten past year MSUDs. Dual latent class analysis regression was used to examine associations between profiles of ACEs and MSUDs. Given gender differences in ACEs and MSUDs, analyses were conducted separately for females and males. Results: Four profiles of ACEs and three profiles of MSUDs were selected for both genders. The four profiles of ACEs were characterized by the following probabilities: high multiple ACEs, high parental substance abuse, high childhood physical abuse, and low ACEs. The three profiles of MSUDs were characterized by the following probabilities: high multiple MSUDs for females and low MSUDs except alcohol use disorders for males, moderate-to-high major depressive episode, and low MSUDs. When compared to the low ACEs and MSUDs profiles, members in the higher ACEs profiles had 3.71–89.75 times greater odds of also being members in the higher MSUDs profiles. However, more than one-third of members in the high multiple ACEs profiles were also in the low MSUDs profiles. Conclusions: Study findings suggest four profiles of the ACEs widely studied as part of the Adverse Childhood Experiences study and risk and resilience for recent MSUDs among men and women nationally affected by ACEs