The Use of Propensity Score Methods to Address Confounding by Provider

For research questions regarding the real-world effectiveness and safety of medical therapies and devices, researchers must often rely on observational data. Unlike controlled clinical trials, the assignment of treatment to patients in routine medical practice is not randomized. One class of methods used extensively by researchers to address this selection problem is propensity score methods. The role of the healthcare provider has not typically been accounted for when propensity score methods are employed, despite the fact that provider, by imparting an effect on both patient-level treatment assignment and patient-level outcomes, is a potential confounding factor. When a healthcare provider has measurable impacts on both a patient’s treatment assignment and their downstream outcomes, simulation results demonstrated that not accounting for these provider effects could lead to biased estimates of treatment effect when using propensity score methods. This was true specifically when a provider’s direct effect on treatment was correlated with their effect on outcome; a situation that occurs when providers having better patient outcomes use therapies at higher (or lower) rates than other providers. Propensity score methods that incorporated provider were able to control this error. Even when provider effects on treatment and outcome were uncorrelated, it was still important to account for provider in the propensity score treatment model. Failure to do so resulted in confidence intervals around the estimated treatment effect that were either substantially too wide or too narrow, depending on the estimation methods used. A criticism of typical 1:1 propensity score matching, whether stratified by provider or not, is that the data from many patients are not utilized in the outcomes analysis. Full matching addresses this issue by optimally assigning all treated patients and all comparison patients into variably-sized matched sets. The result is closer matches between study groups than those obtained by other matching methods. Full matching is not currently utilized frequently because it is difficult to implement. A macro to perform full matching by leveraging SAS optimization procedures is presented.Doctor of Public Healt

Long‐Term Outcomes Among Elderly Survivors of Out‐of‐Hospital Cardiac Arrest

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139093/1/jah31396_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139093/2/jah31396.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139093/3/jah31396-sup-0001-SupInfo.pd

Fatigue in HIV-Infected People: A Three-Year Observational Study

HIV-related fatigue remains the most frequent complaint of seropositive patients

Differences in health care use and outcomes by the timing of in-hospital worsening heart failure

BACKGROUND: Patients hospitalized with acute heart failure may experience worsening symptoms requiring escalation of therapy. In-hospital worsening heart failure is associated with worse in-hospital and postdischarge outcomes, but associations between the timing of worsening heart failure and outcomes are unknown. METHODS: Using data from a large clinical registry linked to Medicare claims, we examined characteristics, outcomes, and costs of patients hospitalized for acute heart failure. We defined in-hospital worsening heart failure by the use of inotropes or intravenous vasodilators or initiation of mechanical circulatory support, hemodialysis, or ventilation. The study groups were early worsening heart failure (n = 1,990), late worsening heart failure (n = 4,223), complicated presentation (n = 15,361), and uncomplicated hospital course (n = 41,334). RESULTS: Among 62,908 patients, those with late in-hospital worsening heart failure had higher in-hospital and postdischarge mortality than patients with early worsening heart failure or complicated presentation. Those with early or late worsening heart failure had more frequent all-cause and heart failure readmissions at 30 days and 1 year, with resultant higher costs, compared with patients with an uncomplicated hospital course. CONCLUSION: Although late worsening heart failure was associated with the highest mortality, both early and late worsening heart failures were associated with more frequent readmissions and higher health care costs compared to uncomplicated hospital course. Prevention of worsening heart failure may be an important focus in the care of hospitalized patients with acute heart failure

Physiological and Psychosocial Factors that Predict HIV-Related Fatigue

Fatigue is one of the most common and debilitating symptoms experienced by HIV-infected people. We report the results of our longitudinal analysis of physiological and psychosocial factors that were thought to predict changes in HIV-related fatigue in 128 participants over a 1-year period, in an effort to sort out the complex interplay among a comprehensive set of physiological and psychosocial variables. Physiological measures included hepatic function (aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transpeptidase, alkaline phosphatase, total bilirubin, hepatitis C status), thyroid function (thyroid stimulating hormone, thyroxine), HIV viral load, immunologic function (CD4, CD8, CD4/CD8 ratio, CD16, CD8CD38), gonadal function (testosterone, dehydroepiandrosterone), hematologic function (hemoglobin, hematocrit, serum erythropoietin), and cellular injury (lactic acid). Psychosocial measures included childhood and adult trauma, anxiety, depression, social support, stressful life events, and post-traumatic stress disorder (PTSD). Unemployment, not being on antiretroviral therapy, having fewer years since HIV diagnosis, more childhood trauma, more stressful life events, less social support, and more psychological distress (e.g., PTSD, anxiety and depression) put HIV-infected persons at risk for greater fatigue intensity and fatigue-related impairment in functioning during 1-year follow-up. Physiological variables did not predict greater fatigue. Stressful life events had both direct and indirect effects on fatigue

Food web persistence is enhanced by non-trophic interactions.

The strength of interspecific interactions is often proposed to affect food web stability, with weaker interactions increasing the persistence of species, and food webs as a whole. However, the mechanisms that modify interaction strengths, and their effects on food web persistence are not fully understood. Using food webs containing different combinations of predator, prey, and nonprey species, we investigated how predation risk of susceptible prey is affected by the presence of species not directly trophically linked to either predators or prey. We predicted that indirect alterations to the strength of trophic interactions translate to changes in persistence time of extinction-prone species. We assembled interaction webs of protist consumers and turbellarian predators with eight different combinations of prey, predators and nonprey species, and recorded abundances for over 130 prey generations. Persistence of predation-susceptible species was increased by the presence of nonprey. Furthermore, multiple nonprey species acted synergistically to increase prey persistence, such that persistence was greater than would be predicted from the dynamics of simpler food webs. We also found evidence suggesting increased food web complexity may weaken interspecific competition, increasing persistence of poorer competitors. Our results demonstrate that persistence times in complex food webs cannot be predicted from the dynamics of simplified systems, and that species not directly involved in consumptive interactions likely play key roles in maintaining persistence. Global species diversity is currently declining at an unprecedented rate and our findings reveal that concurrent loss of species that modify trophic interactions may have unpredictable consequences for food web stability

Learning difficulties : a portuguese perspective of a universal issue

In this article we present findings of a study that was conducted with the purpose of deepening the knowledge about the field of learning difficulties in Portugal. Therefore, within these findings we will discuss across several cultural boundaries, themes related with the existence of learning difficulties as a construct, the terminology, the political, social and scientific influences on the field, and the models of identification and of ongoing school support for students. While addressing the above-mentioned themes we will draw attention to the different, yet converging, international understandings of learning difficulties

Visual-motor integration and reading Chinese in children with/without dyslexia

This is a post-peer-review, pre-copyedit version of an article published in Reading and Writing. The final authenticated version is available online at: https://link.springer.com/article/10.1007/s11145-018-9876-zNational Natural Science Foundation of China; Beijing Advanced Innovation Center for Imaging Technology; Scientific Foundation of Institute of Psychology; Chinese Academy of Sciences