Publications by authors named "Yanxun Xu"

In applications such as biomedical studies, epidemiology, and social sciences, recurrent events often co-occur with longitudinal measurements and a terminal event, such as death. Therefore, jointly modeling longitudinal measurements, recurrent events, and survival data while accounting for their dependencies is critical. While joint models for the three components exist in statistical literature, many of these approaches are limited by heavy parametric assumptions and scalability issues.

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Globally, people with HIV (PWH) experience a broad spectrum of cognitive impairment that can be noted both before and after initiation of antiretroviral therapy (ART). Sex differences in immune function have been implicated in differential cognitive outcomes. Here, we report sex differences in cerebrospinal fluid (CSF) markers in relation to cognitive performance in a subset of ART-naïve PWH participating in the Rakai Neurology Cohort Study.

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Article Synopsis
  • - The study aimed to create a refined method for harmonizing cognitive data from various large-scale studies involving people with HIV (PWH), addressing the inconsistencies in cognitive test assessments across different studies.
  • - A new harmonization technique was developed using a second-order factor model, which helped overcome challenges posed by the absence of common cognitive tests, ensuring reliable comparison across studies like WIHS, MACS, and others.
  • - The results showed that the harmonized cognitive scores were consistent across diverse demographics and accurately reflected variations due to factors like age and education while maintaining the integrity of participants' cognitive development over time.
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Study Design: Retrospective cohort study.

Objective: To characterize variation in dexamethasone and remdesivir use over time among hospitals.

Background: Little is known about hospital-level variation in COVID-19 drug treatments in a large and diverse network in the United States.

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Numerous adverse effects (e.g., depression) have been reported for combination antiretroviral therapy (cART) despite its remarkable success in viral suppression in people with HIV (PWH).

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It has become consensus that mild cognitive impairment (MCI), one of the early symptoms onset of Alzheimer's disease (AD), may appear 10 or more years after the emergence of neuropathological abnormalities. Therefore, understanding the progression of AD biomarkers and uncovering when brain alterations begin in the preclinical stage, while patients are still cognitively normal, are crucial for effective early detection and therapeutic development. In this paper, we develop a Bayesian semiparametric framework that jointly models the longitudinal trajectory of the AD biomarker with a changepoint relative to the occurrence of symptoms onset, which is subject to left truncation and right censoring, in a heterogeneous population.

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Introduction: In the USA, minoritised communities (racial and ethnic) have suffered disproportionately from COVID-19 compared with non-Hispanic white communities. In a large cohort of patients hospitalised for COVID-19 in a healthcare system spanning five adult hospitals, we analysed outcomes of patients based on race and ethnicity.

Methods: This was a retrospective cohort analysis of patients 18 years or older admitted to five hospitals in the mid-Atlantic area between 4 March 2020 and 27 May 2022 with confirmed COVID-19.

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We propose a Bayesian tensor-on-tensor regression approach to predict a multidimensional array (tensor) of arbitrary dimensions from another tensor of arbitrary dimensions, building upon the Tucker decomposition of the regression coefficient tensor. Traditional tensor regression methods making use of the Tucker decomposition either assume the dimension of the core tensor to be known or estimate it via cross-validation or some model selection criteria. However, no existing method can simultaneously estimate the model dimension (the dimension of the core tensor) and other model parameters.

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Offline reinforcement learning (RL) is a promising approach for training intelligent medical agents to learn treatment policies and assist decision making in many healthcare applications, such as scheduling clinical visits and assigning dosages for patients with chronic conditions. In this paper, we investigate the potential usefulness of Decision Transformer (Chen et al., 2021)-a new offline RL paradigm-in medical domains where decision making in continuous time is desired.

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Combination antiretroviral therapy (ART) with at least three different drugs has become the standard of care for people with HIV (PWH) due to its exceptional effectiveness in viral suppression. However, many ART drugs have been reported to associate with neuropsychiatric adverse effects including depression, especially when certain genetic polymorphisms exist. Pharmacogenetics is an important consideration for administering combination ART as it may influence drug efficacy and increase risk for neuropsychiatric conditions.

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Article Synopsis
  • The study investigates the link between antiretroviral therapy (ART) and depressive symptoms in women with HIV, focusing on both somatic and nonsomatic symptoms.
  • It analyzes data from the Women's Interagency HIV Study, categorizing participants into groups based on their depression screening results and utilizing advanced Bayesian machine learning methods to evaluate ART's impact.
  • Results show that certain ART combinations are linked to higher somatic depressive symptoms in women with chronic depression, while no associations were found in those with infrequent or no depression, highlighting the need for future research on specific symptoms and drug combinations.
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Multivariate functional data arise in a wide range of applications. One fundamental task is to understand the causal relationships among these functional objects of interest. In this paper, we develop a novel Bayesian network (BN) model for multivariate functional data where conditional independencies and causal structure are encoded by a directed acyclic graph.

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Importance: Many pulse oximeters have been shown to overestimate oxygen saturation in persons of color, and this phenomenon has potential clinical implications. The relationship between overestimation of oxygen saturation with timing of COVID-19 medication delivery and clinical outcomes remains unknown.

Objective: To investigate the association between overestimation of oxygen saturation by pulse oximetry and delay in administration of COVID-19 therapy, hospital length of stay, risk of hospital readmission, and in-hospital mortality.

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Introduction: High-inflammation subgroups of patients with psychosis demonstrate cognitive deficits and neuroanatomical alterations. Systemic inflammation assessed using IL-6 and C-reactive protein may alter functional connectivity within and between resting-state networks, but the cognitive and clinical implications of these alterations remain unknown. We aim to determine the relationships of elevated peripheral inflammation subgroups with resting-state functional networks and cognition in psychosis spectrum disorders.

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Elevated markers of peripheral inflammation are common in psychosis spectrum disorders and have been associated with brain anatomy, pathology, and physiology as well as clinical outcomes. Preliminary evidence suggests a link between inflammatory cytokines and C-reactive protein (CRP) with generalized cognitive impairments in a subgroup of individuals with psychosis. Whether these patients with elevated peripheral inflammation demonstrate deficits in specific cognitive domains remains unclear.

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Objective: Sexual and physical abuse are highly prevalent among women living with HIV (WLWH) and are risk factors for the development of mental health and substance use disorders (MHDs, SUDs), and cognitive and medical comorbidities. We examined empirically derived patterns of trauma, MHD, and SUD, and associations with later cognitive and health outcomes.

Methods: A total of 1027 WLWH (average age = 48.

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Federated learning is becoming increasingly more popular as the concern of privacy breaches rises across disciplines including the biological and biomedical fields. The main idea is to train models locally on each server using data that are only available to that server and aggregate the model (not data) information at the global level. While federated learning has made significant advancements for machine learning methods such as deep neural networks, to the best of our knowledge, its development in sparse Bayesian models is still lacking.

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Article Synopsis
  • * In a study with 369 women, various T-cell conditions were correlated with cognitive performance and mental health, showing that certain T-cell states impacted attention, memory, stress, and depression levels.
  • * Findings highlight that CD4 and CD8 T-cell activation and exhaustion can influence neuropsychological health, suggesting immune system status plays a role in mental health challenges faced by women living with HIV.
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Background And Objectives: Current clinical guidelines recommend thromboprophylaxis for adults hospitalized with coronavirus disease 2019 (COVID-19), yet it is unknown whether higher doses of thromboprophylaxis offer benefits beyond standard doses.

Methods: We studied electronic health records from 50 091 adults hospitalized with COVID-19 in the United States between February 2020 and February 2021. We compared standard (enoxaparin 30 or 40 mg/day, fondaparinux 2.

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Access and adherence to antiretroviral therapy (ART) has transformed the face of HIV infection from a fatal to a chronic disease. However, ART is also known for its side effects. Studies have reported that ART is associated with depressive symptomatology.

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Background: HIV infection results in immunometabolic reprogramming. While we are beginning to understand how this metabolic reprogramming regulates the immune response to HIV infection, we do not currently understand the impact of ART on immunometabolism in people with HIV (PWH).

Methods: Serum obtained from HIV-infected ( = 278) and geographically matched HIV seronegative control subjects ( = 300) from Rakai Uganda were used in this study.

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Importance: Pulse oximetry guides triage and therapy decisions for COVID-19. Whether reported racial inaccuracies in oxygen saturation measured by pulse oximetry are present in patients with COVID-19 and associated with treatment decisions is unknown.

Objective: To determine whether there is differential inaccuracy of pulse oximetry by race or ethnicity among patients with COVID-19 and estimate the association of such inaccuracies with time to recognition of eligibility for oxygen threshold-specific COVID-19 therapies.

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Cardiometabolic disorders have known inflammatory implications, and peripheral measures of inflammation and cardiometabolic disorders are common in persons with psychotic disorders. Inflammatory signatures are also related to neurobiological and behavioral changes in psychosis. Relationships between systemic inflammation and cardiometabolic genetic risk in persons with psychosis have not been examined.

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