104 research outputs found
A comparison of mixed-models for the analysis of non-linear longitudinal data: application to late-life cognitive trajectories
Several mixed-effects models for longitudinal data have been proposed to
accommodate the non-linearity of late-life cognitive trajectories and assess
the putative influence of covariates on it. No prior research provides a
side-by-side examination of these models to offer guidance on their proper
application and interpretation. In this work, we examined five statistical
approaches previously used to answer research questions related to non-linear
changes in cognitive aging: the linear mixed model (LMM) with a quadratic term,
LMM with splines, the functional mixed model, the piecewise linear mixed model,
and the sigmoidal mixed model. We first theoretically describe the models.
Next, using data from two prospective cohorts with annual cognitive testing, we
compared the interpretation of the models by investigating associations of
education on cognitive change before death. Lastly, we performed a simulation
study to empirically evaluate the models and provide practical recommendations.
Except for the LMM-quadratic, the fit of all models was generally adequate to
capture non-linearity of cognitive change and models were relatively robust.
Although spline-based models have no interpretable nonlinearity parameters,
their convergence was easier to achieve, and they allow graphical
interpretation. In contrast, piecewise and sigmoidal models, with interpretable
non-linear parameters, may require more data to achieve convergence.Comment: 34 pages, 7 Figures, 1 Tabl
Preventing Zoonotic Influenza Virus Infection
We evaluated 49 swine industry workers and 79 nonexposed controls for antibodies to swine influenza viruses. Multivariate modeling showed that workers who seldom used gloves (odds ratio [OR] 30.3) or who smoked (OR 18.7) most frequently had evidence of previous H1N1 swine virus. These findings may be valuable in planning for pandemic influenza
Occupational Exposure to Streptococcus suis among US Swine Workers
Despite numerous cases of human infection with Streptococcus suis worldwide, human disease is rarely diagnosed in North America. We studied 73 swine-exposed and 67 non–swine-exposed US adults for antibodies to S. suis serotype 2. Serologic data suggest that human infection with S. suis occurs more frequently than currently documented
Human Metapneumovirus, Peru
We retrospectively studied 420 pharyngeal swab specimens collected from Peruvian and Argentinean patients with influenzalike illness in 2002 and 2003 for evidence of human metapneumovirus (HMPV). Twelve specimens (2.3%) were positive by multiple assays. Six specimens yielded HMPV isolates. Four of the 6 isolates were of the uncommon B1 genotype
Methicillin-Resistant Staphylococcus aureus (MRSA) Strain ST398 Is Present in Midwestern U.S. Swine and Swine Workers
BACKGROUND: Recent research has demonstrated that many swine and swine farmers in the Netherlands and Canada are colonized with MRSA. However, no studies to date have investigated carriage of MRSA among swine and swine farmers in the United States (U.S.). METHODS: We sampled the nares of 299 swine and 20 workers from two different production systems in Iowa and Illinois, comprising approximately 87,000 live animals. MRSA isolates were typed by pulsed field gel electrophoresis (PFGE) using SmaI and EagI restriction enzymes, and by multi locus sequence typing (MLST). PCR was used to determine SCCmec type and presence of the pvl gene. RESULTS: In this pilot study, overall MRSA prevalence in swine was 49% (147/299) and 45% (9/20) in workers. The prevalence of MRSA carriage among production system A's swine varied by age, ranging from 36% (11/30) in adult swine to 100% (60/60) of animals aged 9 and 12 weeks. The prevalence among production system A's workers was 64% (9/14). MRSA was not isolated from production system B's swine or workers. Isolates examined were not typeable by PFGE when SmaI was used, but digestion with EagI revealed that the isolates were clonal and were not related to common human types in Iowa (USA100, USA300, and USA400). MLST documented that the isolates were ST398. CONCLUSIONS: These results show that colonization of swine by MRSA was very common on one swine production system in the midwestern U.S., suggesting that agricultural animals could become an important reservoir for this bacterium. MRSA strain ST398 was the only strain documented on this farm. Further studies are examining carriage rates on additional farms
Genotype Prevalence and Risk Factors for Severe Clinical Adenovirus Infection, United States 2004-2006
Recently, epidemiological and clinical data have revealed important changes with regard to clinical adenovirus infection, including alterations in antigenic presentation, geographical distribution, and virulence of the virus
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