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Multivariable Regression Models (multivariable + regression_models)
Selected AbstractsEvaluation of factors influencing membrane performanceENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 4 2005Weihua Peng Abstract Three commercial water treatment membranes, TFC-S (Koch membranes, San Diego, CA), ESPA1, and NTR7450 (Hydranautics, San Diego, CA), were tested under various physical and chemical conditions to investigate their fouling behaviors. It was found that TFC-S always displayed the greatest rate of flux decline, ESPA1 displayed a mild trend in flux decline, and NTR7450 presented a nearly stable flux. Multivariable regression models showed that the flux decline rates for TFC-S and ESPA1 were controlled by the initial permeate flux, whereas their initial (that is, instantaneous) foulings were controlled by the interaction between permeate drag and electrostatic repulsions. Feed bacteria concentration also contributed to the initial fouling of ESPA1 as a result of cell deposition on the membrane surface. NTR7450 showed an initial decline in flux followed by a steady flux, and its initial fouling was significantly affected by feed water total organic carbon (TOC) arising from the initial accumulation of colloidal organic particles on the surface. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Mothers without Companionship During Childbirth: An Analysis within the Millennium Cohort StudyBIRTH, Issue 4 2008Holly N. Essex MSc ABSTRACT: Background: Studies have highlighted the benefits of social support during labor but no studies focused on women who choose to be unaccompanied or who have no companion available at birth. Our goals were, first, to identify characteristics of women who are unaccompanied at birth and compare these to those who had support and, second, to establish whether or not being unaccompanied at birth is a risk marker for adverse maternal and infant health outcomes. Methods: The sample comprised 16,610 natural mother-infant pairs, excluding women with planned cesarean sections in the Millennium Cohort Study. Multivariable regression models were used to examine, first, sociodemographic, cultural, socioeconomic, and pregnancy characteristics in relation to being unaccompanied and, second, being unaccompanied at birth in relation to labor and delivery outcomes, maternal health and health-related behaviors, parenting, and infant health and development. Results: Mothers who were single (vs not single), multiparous (vs primiparous), of black or Pakistani ethnicity (vs white), from poor households (vs nonpoor), with low levels of education (vs high levels), and who did not attend antenatal classes (vs attenders) were at significantly higher risk of being unaccompanied at birth. Mothers unaccompanied at birth were more likely to have a preterm birth (vs term), an emergency cesarean section (vs spontaneous vaginal delivery) and spinal pain relief or a general anesthetic (vs no pain relief), a shorter labor, and lower satisfaction with life (vs high satisfaction) at 9 months postpartum. Their infants had significantly lower birthweight and were at higher risk of delayed gross motor development (vs normal development). Conclusions: Being unaccompanied at birth may be a useful marker of high-risk mothers and infants in need of additional support in the postpartum period and beyond. (BIRTH 35:4 December 2008) [source] Association between quality of life scores and short-term outcome after surgery for cancer of the oesophagus or gastric cardiaBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 12 2005J. M. Blazeby Background: Evidence suggests that baseline quality of life (QOL) scores are independently prognostic for survival in patients with cancer, but the role of QOL data in predicting short-term outcome after surgery is uncertain. This study assessed the association between QOL scores and short-term outcomes after surgery for oesophageal and gastric cancer. Methods: Consecutive patients selected for oesophagectomy or total gastrectomy between November 2000 and May 2003 completed the European Organization for Research and Treatment of Cancer's quality of life questionnaire, QLQ-C30. Multivariable regression models, adjusting for known clinical risk factors, were used to investigate relationships between QOL scores, major morbidity, hospital stay and survival status at 6 months. Results: Of 130 patients, 121 completed the questionnaire (response rate 93·1 per cent). There were 29 major complications (24·0 per cent) and 22 patients (18·2 per cent) died within 6 months of operation. QOL scores were not associated with major morbidity but were significantly related to survival status at 6 months after adjusting for known clinical risk factors. A worse fatigue score of 10 points (scale 0,100) corresponded to an increase in the odds of death within 6 months of surgery of 37·4 (95 per cent confidence interval (c.i.) 12·4 to 67·8) per cent (P = 0·002). Pretreatment social function scores were moderately associated with hospital stay (P = 0·021); a reduction in social function by 10 points corresponded to an increase in hospital stay of 0·93 (95 per cent c.i. 0·12 to 1·74) days. Conclusion: QOL scores supplement standard staging procedures for oesophageal and gastric cancer by providing prognostic information, but they do not contribute to perioperative risk assessment. Copyright © 2005 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Racial and Gender Trends in the Use of Implantable Cardioverter-Defibrillators Among Medicare Beneficiaries Between 1997 and 2003CONGESTIVE HEART FAILURE, Issue 2 2009Paul S. Chan MD Differences in the use of implantable cardioverter-defibrillators (ICDs) have been reported, but the extent to which they have widened after the publication of major clinical trials supporting their use is unclear. Using data on Medicare beneficiaries, the authors determined annual age-standardized population-based utilization rates of ICDs for white men, black men, white women, and black women from 1997 to 2003. During the study period, overall use of ICDs increased most for white men (81.7,254.7 procedures per 100,000 from 1997 to 2003) and black men (38.0,151.7 procedures per 100,000), with white women (28.9,98.4 procedures per 100,000) and black women (18.2,77.3 procedures per 100,000) showing smaller increases in comparison. After adjustment with multivariable regression models, differences in utilization rates between whites and men widened compared with blacks and women between 1997 and 2003, a period when indications for ICD therapy have expanded. [source] Impact of Provider Self-Management Education, Patient Self-Efficacy, and Health Status on Patient Adherence in Heart Failure in a Veterans Administration PopulationCONGESTIVE HEART FAILURE, Issue 1 2008Usha Subramanian MD To address the need for more information on predictors of adherence to heart failure (HF) self-management regimens, this study analyzed surveys completed by 259 HF patients receiving care at 2 Veterans Affairs hospitals in 2003. Linear multivariable regression models were used to examine general health status, HF-specific health status (Kansas City Cardiomyopathy Questionnaire) self-management education, and self-efficacy as predictors of self-reported adherence to salt intake and exercise regimens. Self-management education was provided most often for salt restriction (87%) followed by exercise (78%). In multivariable regression analyses, education about salt restriction (P=.01), weight reduction (P=.0004), self-efficacy (P=.03), and health status (P=.003) were significantly associated with patient-reported adherence to salt restriction. In a similar model, self-efficacy (P=.006) and health status (P,.0001), but not exercise education, were significantly associated with patient-reported exercise adherence. Findings suggest that provider interventions may lead to improved adherence with HF self-management and thus improvements in patients' health. [source] Effect of Prescription Drug Coverage on Health of the ElderlyHEALTH SERVICES RESEARCH, Issue 5p1 2008Nasreen Khan Objective. To estimate the effect of prescription drug insurance on health, as measured by self-reported poor health status, functional disability, and hospitalization among the elderly. Data. Analyses are based on a nationally representative sample of noninstitutionalized elderly (,65 years of age) from the Medicare Current Beneficiary Survey (MCBS) for years 1992,2000. Study Design. Estimates are obtained using multivariable regression models that control for observed characteristics and unmeasured person-specific effects (i.e., fixed effects). Principal Findings. In general, prescription drug insurance was not associated with significant changes in self-reported health, functional disability, and hospitalization. The lone exception was for prescription drug coverage obtained through a Medicare HMO. In this case, prescription drug insurance decreased functional disability slightly. Among those elderly with chronic illness and older (71 years or more) elderly, prescription drug insurance was associated with slightly improved functional disability. Conclusions. Findings suggest that prescription drug coverage had little effect on health or hospitalization for the general population of elderly, but may have some health benefits for chronically ill or older elderly. [source] Early wheeze as reported by mothers and lung function in 4-year-olds.PEDIATRIC PULMONOLOGY, Issue 9 2010Prospective cohort study in Krakow Abstract The purpose of the study was to check the hypothesis that early wheezing as reported by mothers would be associated with reduced lung function in 4-year olds. Study participants were recruited prenatally, as part of a prospective cohort study on the respiratory health of young children exposed to various ambient air pollutants. After delivery, infants were followed over 4 years and the interviewers visited participants at their home to record respiratory symptoms every 3 months in the child's first 2 years of life and every 6 months in the 3rd and 4th years. In the 4th year of follow-up, children were invited for standard lung function testing by spirometry quantified by forced vital capacity (FVC), forced expiratory volume in 1,sec (FEV1), and forced expiratory volume in 0.5,sec (FEV0.5) levels. Out of 258 children attending spirometry testing 139 performed at least two acceptable exhalation efforts. Cohort children with acceptable spirometric measurements did not differ with respect to wheezing experience and exposure characteristics from those without. The study shows that episodic wheeze was reported in 28.1% of 4-year olds, 6.5% had transient wheeze, and 4.3% had recurrent wheeze. There was an increased frequency of wheezing symptoms and their duration in transient and recurrent wheezers. Adjusted multivariable regression models for gender and height showed that children who reported more than two episodes of wheezing at any point over the follow-up had FVC values lower by 120.5,ml (P,=,0.016) and FEV1 values lower by 98.3,ml (P,=,0.034) compared to those who did not report any wheezing; children experiencing more than 10 wheezing days by age 4 showed FVC deficit of 87.4,ml (P,=,0.034) and FEV1 values of 65.7,ml (P,=,0.066). The ratios of FEV1/FVC%, and FEV0.5/FVC% were neither associated with wheezing episodes nor wheezing days. In recurrent wheezers, lung function decrement amounted to 207,ml of FVC, 175,ml of FEV1, and 104,ml of FEV0.5. In conclusion, our findings show that wheezing experience during early postnatal life may be associated with lung function deficit of restrictive character in preschool children and detailed history of wheeze in early postnatal life, even though not physician-confirmed, may help define the high risk group of children for poor lung function testing. Pediatr. Pulmonol. 2010; 45:919,926. © 2010 Wiley-Liss, Inc. [source] The Performance of Risk Prediction ModelsBIOMETRICAL JOURNAL, Issue 4 2008Thomas A. Gerds Abstract For medical decision making and patient information, predictions of future status variables play an important role. Risk prediction models can be derived with many different statistical approaches. To compare them, measures of predictive performance are derived from ROC methodology and from probability forecasting theory. These tools can be applied to assess single markers, multivariable regression models and complex model selection algorithms. This article provides a systematic review of the modern way of assessing risk prediction models. Particular attention is put on proper benchmarks and resampling techniques that are important for the interpretation of measured performance. All methods are illustrated with data from a clinical study in head and neck cancer patients. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impact of renal dysfunction on operative mortality following endovascular abdominal aortic aneurysm surgery,BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 2 2007R. G. Statius van Eps Background: Preoperative renal dysfunction is a significant risk factor for death after open abdominal aortic aneurysm repair. The aim of this study was to determine whether renal dysfunction also affected mortality after endovascular aneurysm repair. Methods: Patients from the EUROSTAR registry were stratified into two groups: 4198 with normal renal function (creatinine less than 133 µmol/ml) and 969 with renal dysfunction (serum creatinine more than 133 µmol/ml). Patient characteristics and postoperative complications in the two groups were compared and the effect of renal dysfunction on operative mortality was analysed by multivariable regression models. Results: Patients with renal dysfunction had significantly more co-morbidities, including cardiac and pulmonary impairment. Thirty-day mortality was significantly higher in the group with renal dysfunction (6·2 versus 2·0 per cent; P < 0·001). A significant increase in mortality (5·5 per cent) was also seen in patients with moderate renal dysfunction (serum creatinine 133,265 µmol/ml). After adjustment for age and other risk factors, renal dysfunction was still an independent risk factor for 30-day mortality (odds ratio 2·3, 95 per cent confidence interval 1·6 to 3·3; P < 0·001). Conclusion: Renal dysfunction was a significant and independent risk factor for death after endovascular aneurysm repair. Copyright © 2006 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] | ||||||||||