SEARCH · PubMed Health

Results for “multiple linear regression”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 721 records · Page 40Linked to original sources

PubMed2000

Cost analysis of neuromuscular blocking agents in the operating room: cisatracurium, atracurium, vecuronium and rocuronium.

Cisatracurium (C), Atracurium (A), Rocuronium (R) and Vecuronium (V) are four neuromuscular blockers (NMB) used in the operating room with similar efficacy, defined as adequate muscle relaxation, but different pharmacokinetics. C and A have organ-independent elimination, A is associated with histamine release and R has a shorter onset time. The objective of this study was to economically compare these four NMB from the hospital point of view in order to facilitate drug selection. A cost analysis was performed. Only direct costs were considered and data were collected through a retrospective chart review. A total of 151 patient charts were randomly selected. Differences between patients receiving one of the four NMB were evaluated by ANOVA or Kruskal-Wallis tests. Then a multiple linear regression analysis was conducted. In the chart review, no significant difference was observed between the four groups of patients in age, weight or surgery duration (p > 0.05). Multiple regression analysis revealed that atracurium was on average PTA 237 (1 Euro = PTA 166) cheaper per surgery than any other NMB after adjusting for other factors (p < 0.01) and there is no significant difference in cost between the other three NMBs (p > 0.1). We recommend the use of rocuronium when a quick onset is needed and the patient does not have hepatic failure, cisatracurium when a haemodynamic instability is possible and atracurium in the remaining cases. If just one NMB can be included in the drug formulary we would select cisatracurium due to its pharmacological advantages over atracurium with a small increment in cost.

Adult↗

PubMed1986

Determination of an optimal forecast model for ambulance demand using goal programming.

A multistep approach to determining the optimal parameters of an exponential smoothing model was used to forecast emergency medical service (E.M.S.) demand for four counties of South Carolina. Daily emergency and routine (non-emergency) demand data were obtained and forecast statistics generated for each county sampled, using Winters' exponential smoothing model. A goal programme was formulated to combine forecast results for emergency calls with routine call forecasts. The goal programme gave a higher priority to accurate forecasting of emergency demand. The forecast model generated implicitly weights demand by severity and provides a reliable estimate of demand overall. The optimal parameter values for the smoothing model were obtained by minimizing the objective function value of the goal programming problem. The parameter values obtained were used to forecast demand for E.M.S. in the selected counties. The results of the model were compared to those using a multiple linear regression model and a single-objective-based exponential smoothing model for 2 months of data. When compared with two single-objective forecast models, the multiple-objective approach yielded more accurate forecasts and, therefore, was more cost-effective for the planner. The model presents and demonstrates a theoretical approach to improving the accuracy of ambulance demand forecasts. The possible impact of this approach on planning efficiency is discussed.

Ambulances↗

PubMed2006

Quantitative morphologic evaluation of white matter in survivors of childhood medulloblastoma.

In survivors of pediatric brain tumors, cranial radiation therapy can cause a debilitating cognitive decline associated with decreased volume in normal-appearing white matter (NAWM). We applied fractal geometry to quantify white matter (WM) integrity in the brain of medulloblastoma survivors. Fractal features of WM were evaluated by indices of fractal dimensions (FDs) of WM intensity and boundary on T1-weighted magnetic resonance images. The FD index of WM intensity was calculated by using a fractional Brownian motion model, and the FD index of WM boundary was calculated by using a box-counting method. Fractal features of WM on 116 magnetic resonance images of 58 patients with medulloblastoma were investigated at the start of therapy (Start TX) and approximately 2 years later (After TX). Patients were assigned to one of two groups based on change in NAWM volumes. Fractal features in patients with decreased NAWM volume were significantly greater After TX, whereas those in patients with increased NAWM volumes were not. Multiple linear regression analysis showed that fractal features were strongly correlated with NAWM volumes After TX in patients with decreased NAWM volume. These results demonstrated significant deficit in NAWM integrity and WM density changes in children treated for medulloblastoma. Multiple regression analysis illustrated that deficits in NAWM integrity in these children may partly explain the decrease in NAWM volume. We conclude that fractal geometry can be used to monitor the morphologic effects of neurotoxicity in brain tumor survivors.

Adolescent↗

PubMed1995

Binary regression with continuous outcomes.

Clinical research often involves continuous outcome measures, such as blood cholesterol, that are amenable to statistical techniques of analysis based on the mean, such as the t-test or multiple linear regression. Clinical interest, however, frequently focuses on the proportion of subjects who fall below or above a clinically relevant cut-off value, as a measure of the risk of disease. The customary approach to analyse such data is to dichotomize the continuous outcome measure and use statistical techniques based on binary data and the binomial distribution. In this paper, we use a parametric approach and the framework of generalized linear models to fit various regression models, including the logistic, on the basis of the original continuous outcome. We consider the Gaussian and the three-parameter log-normal distributions for the continuous outcome, assessing both precision and bias under various conditions. In simulation analyses, we find that we are unable to fit some of the samples with the 'dichotomous' approach, but we can with the 'continuous' approach, and that the latter yields estimates between 25 and 85 per cent more efficient than the former. We illustrate the method, programmed using GLIM macros, with data from clinical studies of the risk of hypoxaemia during open thoracic surgery and the risk of nocturnal hypoglycaemia among diabetic children.

Diabetes Mellitus, Type 1↗

PubMed2005

Regional differences of melphalan lung levels after isolated lung perfusion in the rat.

BACKGROUND: Efficacy studies of isolated lung perfusion (ILuP) with melphalan showed superior results compared to intravenous therapy. However, the influence of pharmacokinetic parameters on the final melphalan lung concentration (FMLC) is unknown. In this study, we studied the impact of three different perfusion parameters on the FMLC in different areas of the lung. MATERIAL AND METHODS: Fifty-four rats were randomized into nine groups. Each group underwent ILuP with variation of perfusion duration (15, 30, and 60 min), the flow (0.125, 0.25, and 0.5 ml/min), concentration (8.3, 16.7, 33.3, 66.7, and 133.3 microg/ml) and the resulting dose (maximum 4 mg/kg). Lung samples were taken from the hilum and at the periphery of the lung (apex, base). Additional samples were taken to evaluate wet-to-dry ratio (W/D-ratio). Multiple linear regression and Student's t test were used for analysis. Significance was defined as a P<or=0.05. RESULTS: Experiment 1: The W/D-ratio was not influenced by varying the perfusion parameters (P=0.97). Experiment 2: multiple regression led to an equation that predicts FMLC for each area of the lung studied. FMLC is dependent on concentration, perfusion time, and region. CONCLUSION: The influence of the perfusion parameters on FMLC is dependent on the area of the lung perfused. This should be taken into consideration when pulmonary metastases are treated with ILuP.

Animals↗

PubMed2002

Resource utilization for acute lower gastrointestinal hemorrhage: the Ontario GI bleed study.

OBJECTIVES: Acute lower gastrointestinal hemorrhage (LGIH) is a common indication for hospitalization. However, there are few published studies of related health care resource utilization. Resource utilization, length of stay (LOS) and direct medical costs were characterized in a cohort of patients admitted for nonmalignant LGIH to centres in Ontario. METHODS: Consecutive admissions for LGIH were identified at four Ontario hospitals. Profiles of resource utilization, LOS and estimates of direct medical costs were compiled through detailed chart review and adaptation of an administrative database. All centres were participants in the Ontario Case Cost Project. Linear regression models of log-transformed data were constructed to identify demographic variables predictive of LOS and case cost. RESULTS: Among 124 patients enrolled (mean age 58.8 years) the average case cost was dollars 4832 (SD dollars 7187) for 7.5 days in hospital (SD 12.0). Diverticular disease was the bleeding source most often identified (34.6%), followed by hemorrhoids (13.7%) and ischemic colitis (9.7%). Older age and comorbid illness, specifically coronary artery disease (CAD), were associated with both increased LOS and higher case cost in univariate regression analyses. Age persisted as the lone independent predictor of LOS in the multivariate model (P<0.05, R2=0.076), and age and CAD were both independent predictors of cost (P<0.05, R2=0.109) in a stepwise multiple linear regression analysis. Neither sex nor nonsteroidal anti-inflammatory drug use predicted LOS or cost. CONCLUSIONS: Admissions for acute LGIH are associated with significant resource utilization, particularly among elderly patients with CAD.

Acute Disease↗

PubMed2005

Impact of age and basic heart rate on heart rate turbulence in healthy persons.

Postextrasystolic acceleration of heart rate (HR), known as HR turbulence (HRT) is attenuated in patients with coronary artery disease at increased risk of adverse events. The influence of age and basic HR on HRT have not been evaluated in a large cohort of persons. In 95 healthy individuals, HRT onset (TO) and slope (TS) were calculated from 24-hour ambulatory electrocardiograms, as well as the turbulence timing (TT). Gender specific differences in TO and TS were compared in simple, linear, weighted regression model. The influence of age and the basic HR preceding ventricular premature contractions on HRT were examined. We found that, in men and women, TO decreases as basic HR increases (P < 0.01). In contrast, in men, TS decreased as basic HR increases, whereas in women, basic HR influenced TS only slightly (P < 0.01). A multiple, linear regression model revealed a decrease in HRT with increasing age in men. In conclusion, physiological acceleration of the HR within the first 11 beats after premature ventricular complex (VPC) was observed in >75% of healthy individuals. An accelerating HR preceding the VPC influenced HRT in men. An increasing age was associated with a decrease in HRT in men and a decrease in TO in women. These results illustrate the importance of physiological modulations of HRT when used for risk stratification, especially in older populations.

Adult↗

PubMed2005

Correlates of perceived autonomy among elders in a senior citizen home: a cross-sectional survey.

BACKGROUND: Researchers have pointed out several factors that correlated with or influenced autonomy in older people. However, these studies covered only a range of socio-demographic or physical factors, while factors from psychosociological and spiritual domains remain ignored. Also, there is lack of quantitative research and publications in this area. OBJECTIVES: To explore factors related to autonomy among elders in a senior citizen home. DESIGN: A cross-sectional design utilizing a correlational approach was adopted. PARTICIPANTS: A stratified random sample of 121 subjects older than 64 years was recruited at a senior citizen home. METHODS: Questionnaires and interviews were used to collect data. The structured questionnaire consisted of five parts, each gauging socio-demographic information, life attitudes, frequency and satisfaction of social support, and autonomy. Descriptive and stepwise multiple linear regression analysis were used to analyze the data. FINDINGS: Subjects had a high autonomy score (mean = 3.63), with the greatest score in independence (mean = 4.39), followed by individuality (mean = 3.74) and freedom (mean = 3.22). Multiple regression analysis showed that satisfaction of social support (beta = .57), functional ability (beta = .25), life attitudes (beta = .20), and level of education (beta = .14) significantly affected autonomy in these elderly subjects and explained 64.2% of the total variance of autonomy in this population. CONCLUSIONS: Findings from this study indicate that perceived autonomy is influenced by social support, functional ability, life attitude, and literacy among institutionalized elders.

Activities of Daily Living↗

PubMed1995

Methodological considerations in estimating speed of cognitive operations.

Individuals infected with Human Immunodeficiency Virus (HIV) and having cognitive impairment have been described as having slow mentation. Data supporting this proposition come from a variety of sources, including Sternberg's (1966) item recognition memory task. The procedure nominally provides an index of speed of mental operations, independent from input/output demands. However, since the original use of this procedure in the 1960s, advances in cognitive psychology have revealed many of its limitations. The purpose of the present study was to examine the psychometric characteristics of this task. Each participant performed the Sternberg item recognition task twice, 6 mo apart. The stability of the estimate of the slope of regression equations and for zero intercept ranged from excellent (r = .87) to poor (r = .30), and the data from many individual subjects could not be reliably modelled using multiple linear regression techniques. These data, as well as those from previous research, demonstrate the limited practical use of this task in clinical samples. Furthermore, as cognitive psychological theory has advanced in the past 30 yr, the conceptual underpinnings of the procedure have essentially evaporated.

AIDS Dementia Complex↗

PubMed1978

Estimation of body fat and lean body mass from anthropometric dimensions in adult Indian women.

Mean values and standard deviations of body fat and lean body mass of 65 young Indian women aged 20-25 years were 9.00 kg, SD 6.14 and 36.02 kg, SD 3.99 respectively. Body fat per cent was 18.72 SD 10.48. On selective stepwise multiple linear regression analysis, the measurements selected for predicting body fat % were maximum thigh girth, chest diameter, height up to gluteal furrow and shoulder diameter, all four together giving a multiple correlation coefficient of 0.88. For predicting lean body mass, the measurements selected were stature, upper arm length, lower thigh girth and chest diameter, all four together giving a multiple correlation coefficient of 0.84.

Adipose Tissue↗

PubMed2001

Association between size at birth, paediatric diarrhoeal incidence and postnatal growth.

UNLABELLED: This study tests the hypothesis that size at birth is associated with diarrhoeal incidence from birth to 24 mo of age, and the hypothesis that diarrhoeal incidence from birth to 24 mo is associated with body size at age 24 mo. This is a longitudinal study of 1476 infants born in Lahore. Pakistan, in 1984-1987. Diarrhoeal incidence was enumerated monthly. A generalized estimating equations approach with Poisson regression showed that birthlength standard deviation score (SDS) and ponderal index at birth (rate ratio = 1.01 and 1.00; each p > 0.05) were not significantly associated with diarrhoeal incidence. Multiple linear regression showed that diarrhoeal incidence was significantly associated with weight SDS and body mass index at 24 mo (regression coefficient or beta = -0.58 and -1.02: each p < 0.05). but not with height SDS (beta = -0.10: p > 0.05). The associations were mainly due to a transient effect of diarrhoea in the period 18-24 mo. CONCLUSION: Prevention of low birthweight is unlikely to have an impact on diarrhoeal incidence in infants. Control of diarrhoeal incidence may not improve the growth of infants in developing countries.

Birth Weight↗

PubMed1976

Voice predicts affect during psychotherapy.

This study examined the relationship between emotions and the frequency and power characteristics of the voice in psychotherapy. The intensity of fear, anger, depression, and total affect in each of four interviews with one patient was rated every 20 seconds on a nine-point scale. Significant agreement among judges was achieved. Voice samples from each epoch in which there was sufficient speech were subjected to spectral analysis of the frequencies between 0 and 1000 HZ. These spectra were scored for nine frequency and power parameters. Multiple linear regression equations were then developed from two interviews, using the nine voice spectral variables as predictors and the mean ratings for each affect as the criterion variables. Significant multiple correlations were achieved between every rated affect and various combinations of voice variables. The beta weights and constants from these equations were then employed in the successful prediction of levels of anger, fear, depression, and total affect in one interview, and the levels of depression and total affect in another interview. In addition, epochs of conflict differed from "pure" affect epochs, and pure epochs of anger, fear, and depression differed from each other in various frequency and power characteristics of the voice. Voice spectral measures may be an objective means of identifying and quantifying affect in psychotherapy.

Affect↗

PubMed2003

Risk factors for tooth loss in the institutionalised elderly; a six-year cohort study.

OBJECTIVE: The aim of this study was to examine risk factors for tooth loss and edentulism in institutionalised elderly people. DESIGN: Six-year prospective cohort study. SETTING: Twenty nine of the 30 institutions for elderly people in Kitakyushu, Japan. SUBJECTS: Four hundred and eighteen of the 1,096 subjects who were dentate at the baseline examination. OUTCOME MEASURES: Factors that influenced tooth loss and edentulism. RESULTS: In both sexes, older subjects had fewer remaining teeth at baseline. Males lost more teeth than females, and edentulism was also more likely in males than in females. Stepwise multiple linear regression analysis showed that the number of teeth, number of decayed teeth, periodontal pocket depth, and plaque index were significant predictors for the number of teeth lost. The incidence of edentulism was higher in males than in females. Stepwise multiple logistic regression analysis revealed that poorer mental health status, fewer teeth, having deep periodontal pocket, and poorer oral hygiene status were independently associated with the six-year incidence of edentulism. CONCLUSIONS: Tooth loss in institutionalised elderly people in Japan is related to both poor oral health status and poor mental health status.

Aged↗

PubMed1997

Prediction equations do not eliminate systematic error in self-reported body mass index.

Epidemiological studies of the risks of obesity often use body mass index (BMI) calculated from self-reported height and weight. The purpose of this study was to examine the pattern of reporting error associated with self-reported values of BMI and to evaluate the extent to which linear regression models predict measured BMI from self-reported data and whether these models could compensate for this reporting error. We examined measured and self-reported weight and height on 5079 adults aged 30 years to 64 years from the second National Health and Nutrition Examination Survey. Measured and self-reported BMI (kg/m2) was calculated, and multiple linear regression techniques were used to predict measured BMI from self-reported BMI. The error in self-reported BMI (self-reported BMI minus measured BMI) was not constant but varied systematically with BMI. The correlation between measured BMI and the error in self-reported BMI was -0.37 for men and -0.38 for women. The pattern of reporting error was only weakly associated with self-reported BMI, with the correlation being 0.05 for men and -0.001 for women. Error in predicted BMI (predicted BMI minus measured BMI) also varied systematically with measured BMI, but less consistently with self-reported BMI. More complex models only slightly improved the ability to predict measured BMI compared with self-reported BMI alone. None of the equations were able to eliminate the systematic reporting error in determining measured BMI values from self-reported data. The characteristic pattern of error associated with self-reported BMI is difficult or impossible to correct by the use of linear regression models.

Adult↗

PubMed2006

Bone mineral density of the proximal tibia relates to axial torsion in the lower limb.

This study sought to determine the relationship between bone mineral density distribution in the proximal tibia and tibial and femoral torsions, hip-knee-ankle angle, hip rotation index (internal-external rotation), knee abduction moments, and the foot progression angle. Simple linear regression found that the hip rotation index (r=-0.59, p<0.001), tibial torsion (r=-0.41, p=0.004), and knee abduction moments (r=0.39, p=0.005) were significantly related to medial-lateral BMD ratio for all subjects. The three variables were then studied together to determine their relationship to the bone mineral distribution in the proximal tibia using multiple linear regression (r=0.80, p<0.001). These findings suggest that higher medial knee joint loads, loss of internal rotation of the hip, and internal tibial torsion may lead to increased medial versus lateral BMD of the proximal tibia of healthy knees. Similar bone distribution patterns are found in knees with osteoarthritis; therefore, we suggest these may be risk factors.

Adult↗

PubMed2000

Representation of accuracy in the dorsal premotor cortex.

The endpoint accuracy of a reaching movement strongly affects kinematics, particularly during the final phases of movement. However, where and how accuracy is represented in the central nervous system remains unknown. In this study, the discharge of 150 neurons located primarily in the dorsal premotor cortex (PMd), were recorded from monkeys performing an instructed delay, centre-out reaching task in which movement direction and target size were systematically varied. Linear regression analyses were used to assess the dependence of movement kinematics and cell discharge on target direction, size and tangential velocity (i.e. speed). The speed and timing of the movement were dependent on both direction and target size. Initially direction was the dominant predictor whilst target size became more important as the hand reached the target. A temporal multiple linear regression analysis found significant correlations with target size in 99 of 150 cells. The discharge of 134 cells was directionally tuned and 83 cells modulated with mean speed. Significant correlations of discharge with target size occurred throughout the task as did correlations with direction. However, correlations with direction preferentially occurred early in the task, prior to movement onset, whilst correlations with target size tended to occur late, well after movement onset. This temporal dependency of the firing in relationship to target direction and size mirrored that observed for the kinematics. We conclude that the discharge of PMd cells is highly correlated with the accuracy requirement of the movement. The timing of the correlations suggest that accuracy information is available for the planning and for the on-line control of endpoint accuracy.

Action Potentials↗

PubMed1995

Defective natural immunity: an early manifestation of human immunodeficiency virus infection.

Cytotoxicity mediated by natural killer (NK) and lymphokine-activated killer (LAK) cells may be of significance in host defense against viral infections. This study included 347 patients infected with human immunodeficiency syndrome virus (HIV) type 1 and 110 controls. The NK cell activity, either unstimulated or stimulated with interferon-alpha (IFN-alpha) or interleukin-2 (IL-2), and the LAK cell activity were suppressed in patients, but the NK/LAK cell activity did not differ between patients with AIDS and patients without AIDS. However, the IFN-alpha-stimulated NK cell activity and LAK cell activity were reduced in patients with symptoms of HIV disease (CDCIV) when compared with asymptomatic patients (CDCII+III). When the data were analyzed by multiple linear regression, the percentage of CD4+ cells had a positive effect on these two parameters in patients without AIDS, whereas the percentage of CD4+ cells had no significant effect on unstimulated and IL-2-stimulated NK cell activity in these patients. In controls and AIDS patients, the percentage of CD4+ cells had no effect on NK/LAK cell activity in multiple linear models. The total number of CD16+ cells was low in patients compared to controls, whereas the percentages of CD16+, CD56+, and CD16+CD56+ were either normal or elevated. Therefore, the decrease in NK cell subpopulations did not contribute to the observed depression in NK/LAK cell activity in vitro. It is concluded that natural immunity is suppressed in HIV-seropositive patients primarily because of a qualitative defect of the NK/LAK cells. This qualitative defect includes a reduced responsiveness to IFN-alpha, which is progressive until the onset of symptoms, and possibly related to the loss of CD4+ cells.

Adult↗

PubMed2006

Association of ginseng use with survival and quality of life among breast cancer patients.

The authors evaluated the associations of ginseng use as a complementary therapy with survival and quality of life (QOL) in a cohort of 1,455 breast cancer patients who were recruited to the Shanghai Breast Cancer Study between August 1996 and March 1998 in Shanghai, China. Patients were followed through December 2002. Information on ginseng use before cancer diagnosis was collected at baseline recruitment and was linked to survival. Survivors' ginseng use after cancer diagnosis was obtained at the follow-up survey and was correlated to QOL at the same time. The Kaplan-Meier method and Cox regression models were applied to evaluate the association of ginseng use with overall and disease-free survival. The relation of ginseng use and QOL was evaluated by using multiple linear regression models. Approximately 27% of study participants were regular ginseng users before cancer diagnosis. Compared with patients who never used ginseng, regular users had a significantly reduced risk of death; adjusted hazard ratios associated with ginseng use were 0.71 (95% confidence interval: 0.52, 0.98) for total mortality and 0.70 (95% confidence interval: 0.53, 0.93) for disease-specific mortality/recurrence. Ginseng use after cancer diagnosis, particularly current use, was positively associated with QOL scores, with the strongest effect in the psychological and social well-being domains. Additionally, QOL improved as cumulative ginseng use increased.

Adult↗