Search results for "Linear Model"
showing 10 items of 598 documents
Changes of QTc interval after opioid switching to oral methadone.
2013
Abstract A consecutive sample of patients who were switched from strong opioids to methadone in a period of 1 year was surveyed. QTc was assessed before switching (T0) and after achieving adequate analgesia and an acceptable level of adverse effects (Ts). Twenty-eight of 33 patients were switched to methadone successfully. The mean initial methadone doses at T0 were 67.1 mg/day (SD ±80.2, range 12-390). The mean QTc interval at T0 was 400 ms (SD ±30, range 330-450). The mean QTc interval at Ts (median 5 days) was 430 ms (SD ±26, range 390-500). The difference (7.7 %) was significant (p < 0.0005). Only two patients had a QTc of 500 ms. No serious arrhythmia was observed. At the linear regres…
Small animal tumour imaging with MRI and the ECAT EXACT scanner: application of partial volume correction and comparison with microPET data.
2010
Objective Partial volume effects caused by limited spatial resolution of conventional positron emission tomography (PET) scanners result in an underestimation of the activity concentration in small tumours. The aim of the study was to evaluate the feasibility of small animal tumour imaging with the clinical PET scanner ECAT EXACT after partial volume correction based on MRI calculations. The same tumour model was examined additionally with the small animal PET system, microPET focus 120. Methods Before the ECAT EXACT studies recovery coefficients for different sphere volumes were generated with phantom experiments. For the following in-vivo study DS-sarcoma cells were implanted on both hind…
Relation between physical activity and academic performance in 3rd-year secondary education students
2011
The main aim of this study was to analyze the relationship between the amount of physical activity and academic performance in 3rd-year secondary education students. The sample was taken from three secondary schools in the area of Barcelona. 284 students (158 girls, 126 boys) with an average age of 14.7 yr. participated. The International Physical Activity Questionnaire was used by students to self-report their amount of physical activity. Students’ academic records were obtained for comparisons. Results showed that there was a linear relationship between academic performance and physical activity; nevertheless, there was a trend to stronger correlation when modeling the relationship betwee…
Gentamicin alters nitric oxide production in semicircular canals and otolith organs.
2010
Objectives/Hypothesis: Intratympanic application of gentamicin is an important therapeutic option to control vertigo spells in Meniere's disease. Low doses eliminate the function of semicircular canal ampullae (SCCA) and saccule in most patients, although utricular function is maintained in many cases. Local alteration in free radical production might be responsible for these differences. Therefore, the gentamicin-induced nitric oxide (NO) production was determined in an animal model using separate organ cultures of SCCA, saccule, and utricle. Study Design: Prospective pilot study in male guinea pigs. Methods: SCCA, saccule, and utricle of 28 guinea pigs were isolated and incubated separate…
Serum uric acid is not independently associated with plasma renin activity and plasma aldosterone in hypertensive adults
2017
Background and Aims In experimental investigations conducted in rats, raising serum uric acid (SUA) levels resulted in the stimulation of intrarenal renin expression. Studies in humans exploring the association of SUA with plasma renin activity (PRA) yielded conflicting results. Moreover, little is known about the relationship of SUA with plasma aldosterone concentration (PAC). The study aimed to assess the relationship between SUA levels, PRA, and PAC and the influence of age, gender, body mass index (BMI), and hyperuricemia on these relationships in subjects with essential hypertension (EH). Methods and Results We enrolled 372 hypertensive patients (mean age 45 ± 12 years, men 67%) with u…
Protective role of the Mediterranean diet on several cardiovascular risk factors: Evidence from Sicily, southern Italy
2014
Background and aims: Epidemiological studies conducted in European countries demonstrated that the adoption of a Mediterranean diet protect against clustered risk factors but those evaluating such benefits specifically in southern Italy are scarce. Thus, the aim of this study was to assess the association between the adherence to the Mediterranean diet and cardiovascular risk factors obesity, diabetes, and hypertension. Methods and results: A cross-sectional population-based survey including 3090 subjects was conducted in Sicily, southern Italy. Food intake was evaluated through a validated food frequency questionnaire and adherence to the dietary pattern was assessed using the MedDietScore…
Polypharmacy, length of hospital stay, and in-hospital mortality among elderly patients in internal medicine wards. The REPOSI study
2011
PURPOSES: We evaluated the prevalence and factors associated with polypharmacy and investigated the role of polypharmacy as a predictor of length of hospital stay and in-hospital mortality. METHODS: Thirty-eight internal medicine wards in Italy participated in the Registro Politerapie SIMI (REPOSI) study during 2008. One thousand three hundred and thirty-two in-patients aged ≥65 years were enrolled. Polypharmacy was defined as the concomitant use of five or more medications. Linear regression analyses were used to evaluate predictors of length of hospital stay and logistic regression models for predictors of in-hospital mortality. Age, sex, Charlson comorbidity index, polypharmacy, and numb…
Opposites detract: Middle school peer group antipathies
2009
This study examines variability in patterns of peer group antipathy. Same-grade adolescent peer groups were identified from sociometric nominations of preferred affiliates in a community sample of 600 Finnish ninth-grade middle school students (mean age = 15.0 years). Hierarchical linear modeling determined characteristics of youths in actor groups (nominators) that predicted antipathy for youths in target groups (nominatees) on the basis of target group characteristics. Most antipathies were based on dissimilarity between groups representing the mainstream culture and groups opposed to it. The higher a peer group’s school burnout, the more its members disliked students in peer groups with …
Empirical study of the dependence of the results of multivariable flexible survival analyses on model selection strategy
2008
Flexible survival models, which avoid assumptions about hazards proportionality (PH) or linearity of continuous covariates effects, bring the issues of model selection to a new level of complexity. Each ‘candidate covariate’ requires inter-dependent decisions regarding (i) its inclusion in the model, and representation of its effects on the log hazard as (ii) either constant over time or time-dependent (TD) and, for continuous covariates, (iii) either loglinear or non-loglinear (NL). Moreover, ‘optimal’ decisions for one covariate depend on the decisions regarding others. Thus, some efficient model-building strategy is necessary. We carried out an empirical study of the impact of the model …
Spatial Interaction between Neighbouring Counties: Cancer Mortality Data in Valencia (Spain)
1995
The statistical analysis of geographical mortality data has usually been approached via regression models that include appropriate covariates. These models assume stochastic independence of mortality counts for neighbouring sites, a questionable assumption that spatial automodels (Besag, 1974, Journal of the Royal Statistical Society, Series B 36, 192-236) make unnecessary. This paper presents the use of the autopoisson distribution in order to detect spatial interaction between neighbouring sites. If this interaction results in being nonsignificant, the auto-Poisson distribution reduces to a usual Poisson regression model, a particular case of generalized linear models (McCullagh and Nelde…