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Linear Regression (linear + regression)
Kinds of Linear Regression Terms modified by Linear Regression Selected AbstractsGradient Estimation in Volume Data using 4D Linear RegressionCOMPUTER GRAPHICS FORUM, Issue 3 2000László Neumann In this paper a new gradient estimation method is presented which is based on linear regression. Previous contextual shading techniques try to fit an approximate function to a set of surface points in the neighborhood of a given voxel. Therefore a system of linear equations has to be solved using the computationally expensive Gaussian elimination. In contrast, our method approximates the density function itself in a local neighborhood with a 3D regression hyperplane. This approach also leads to a system of linear equations but we will show that it can be solved with an efficient convolution. Our method provides at each voxel location the normal vector and the translation of the regression hyperplane which are considered as a gradient and a filtered density value respectively. Therefore this technique can be used for surface smoothing and gradient estimation at the same time. [source] Estimation Optimality of Corrected AIC and Modified Cp in Linear RegressionINTERNATIONAL STATISTICAL REVIEW, Issue 2 2006Simon L. Davies Summary Model selection criteria often arise by constructing unbiased or approximately unbiased estimators of measures known as expected overall discrepancies (Linhart & Zucchini, 1986, p. 19). Such measures quantify the disparity between the true model (i.e., the model which generated the observed data) and a fitted candidate model. For linear regression with normally distributed error terms, the "corrected" Akaike information criterion and the "modified" conceptual predictive statistic have been proposed as exactly unbiased estimators of their respective target discrepancies. We expand on previous work to additionally show that these criteria achieve minimum variance within the class of unbiased estimators. Résumé Les critères de modèle de sélection naissent souvent de la construction de mesures d'estimation impartiales, ou approximativement impartiales, connues comme divergences globales prévues. De telles mesures quantifient la disparité entre le vrai modèle (c'est-à-dire le modèle qui a produit les données observées) et un modèle candidat correspondant. En ce qui concerne les applications de régression linéaires contenant des erreurs distribuées normalement, le modèle de critère d'information "corrigé" Akaike et le modèle conceptuel de statistique de prévision "modifié" ont été proposés comme étant des instruments exacts de mesures d'estimation impartiales de leurs objectifs respectifs de divergences. En nous appuyant sur les travaux précédents et en les développant, nous proposons de démontrer, en outre, que ces critères réalisent une variance minimum au sein de la classe des instruments de mesures d'estimation impartiales. [source] Are Mechanistic and Statistical QSAR Approaches Really Different?MOLECULAR INFORMATICS, Issue 6-7 2010MLR Studies on 158 Cycloalkyl-Pyranones Abstract Two parallel approaches for quantitative structure-activity relationships (QSAR) are predominant in literature, one guided by mechanistic methods (including read-across) and another by the use of statistical methods. To bridge the gap between these two approaches and to verify their main differences, a comparative study of mechanistically relevant and statistically relevant QSAR models, developed on a case study of 158 cycloalkyl-pyranones, biologically active on inhibition (Ki) of HIV protease, was performed. Firstly, Multiple Linear Regression (MLR) based models were developed starting from a limited amount of molecular descriptors which were widely proven to have mechanistic interpretation. Then robust and predictive MLR models were developed on the same set using two different statistical approaches unbiased of input descriptors. Development of models based on Statistical I method was guided by stepwise addition of descriptors while Genetic Algorithm based selection of descriptors was used for the Statistical II. Internal validation, the standard error of the estimate, and Fisher's significance test were performed for both the statistical models. In addition, external validation was performed for Statistical II model, and Applicability Domain was verified as normally practiced in this approach. The relationships between the activity and the important descriptors selected in all the models were analyzed and compared. It is concluded that, despite the different type and number of input descriptors, and the applied descriptor selection tools or the algorithms used for developing the final model, the mechanistical and statistical approach are comparable to each other in terms of quality and also for mechanistic interpretability of modelling descriptors. Agreement can be observed between these two approaches and the better result could be a consensus prediction from both the models. [source] Prediction of Flash Point Temperature of Pure Components Using a Quantitative Structure,Property Relationship ModelMOLECULAR INFORMATICS, Issue 6 2008Farhad Gharagheizi Abstract In this work, a general Quantitative Structure,Property Relationship (QSPR) model (, , and ) for the prediction of flash points of 1030 pure compounds is developed. Genetic Algorithm-based Multivariate Linear Regression (GA-MLR) technique is used to select four chemical structure-based molecular descriptors from a pool containing 1664 molecular descriptors. [source] A Combinatorial Approach to the Variable Selection in Multiple Linear Regression: Analysis of Selwood et al.MOLECULAR INFORMATICS, Issue 6 2003A Case Study, Data Set Abstract A combinatorial protocol (CP) is introduced here to interface it with the multiple linear regression (MLR) for variable selection. The efficiency of CP-MLR is primarily based on the restriction of entry of correlated variables to the model development stage. It has been used for the analysis of Selwood et al data set [16], and the obtained models are compared with those reported from GFA [8] and MUSEUM [9] approaches. For this data set CP-MLR could identify three highly independent models (27, 28 and 31) with Q2 value in the range of 0.632,0.518. Also, these models are divergent and unique. Even though, the present study does not share any models with GFA [8], and MUSEUM [9] results, there are several descriptors common to all these studies, including the present one. Also a simulation is carried out on the same data set to explain the model formation in CP-MLR. The results demonstrate that the proposed method should be able to offer solutions to data sets with 50 to 60 descriptors in reasonable time frame. By carefully selecting the inter-parameter correlation cutoff values in CP-MLR one can identify divergent models and handle data sets larger than the present one without involving excessive computer time. [source] The relationship between unimanual capacity and bimanual performance in children with congenital hemiplegiaDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 9 2010LEANNE SAKZEWSKI Aim, This study explores the relationship between unimanual capacity and bimanual performance for children with congenital hemiplegia aged 5 to 16 years. It also examines the relationship between impairments and unimanual capacity and bimanual performance. Method, Participants in this cross-sectional study attended a screening assessment before participating in a large, randomized trial. They comprised 70 children with congenital hemiplegia (39 males, 31 females; mean age 10y 6mo, SD 3y); 18 were classified in the Manual Ability Classification System level I, 51 in level II, and one in level III. Eighteen were in Gross Motor Function Classification System, level I and 52 in level II. Sixty-five participants had spasticity and five had dystonia and spasticity. Fifteen typically developing children (7 males, 8 females; mean age 8y 8mo, SD 2y 7mo), matched to study participants for age and sex, were recruited as a comparison group for measures of sensation, grip strength, and movement efficiency. Outcome measures for unimanual capacity were the Melbourne Assessment of Unilateral Upper Limb Function (MUUL), and the Jebsen,Taylor Hand Function Test (JTHFT). The Assisting Hand Assessment (AHA) evaluated bimanual performance. Upper limb impairments were measured using assessments of stereognosis, moving two-point discrimination, spasticity, and grip strength. Results, There was a strong relationship between unimanual capacity (MUUL) and bimanual performance (AHA; r=0.83). Linear regression indicated MUUL and stereognosis accounted for 75% of the variance in AHA logit scores. Sensory measures were moderately correlated with unimanual capacity and bimanual performance. Age, sex, and grip strength did not significantly influence bimanual performance. There was no difference between children with right- and left-sided hemiplegia for motor performance. Interpretation, Findings of our study confirm a strong relationship between unimanual capacity and bimanual performance in a cohort of children with congenital hemiplegia. However, the directionality of the relationship is unknown and therapists cannot assume improvements in unimanual capacity will lead to gains in bimanual performance. [source] Relationship between mean blood glucose and glycated haemoglobin in Type 2 diabetic patientsDIABETIC MEDICINE, Issue 2 2008K. Makris Abstract Aims To correlate the values of MBG to HbA1c in Greek patients with Type 2 diabetes and/or metabolic syndrome. Methods We followed up 140 Greek adult patients: 92 patients with Type 2 diabetes treated with insulin or oral glucose-lowering medication, and 48 patients with newly diagnosed Type 2 diabetes or metabolic syndrome not receiving any treatment. MBG was calculated for each patient from self-measurements of blood glucose using a portable glucometer, made six times a day (before eating and 2 h after a meal), three times a week for 1 month. HbA1c was determined by HPLC at 0 and 12 weeks. Results, HbA1c at 0 (x) and 12 weeks (y) correlated strongly (y = 0.790x + 1.115, r = 0.92), confirming that the patient's glycaemic status remained stable during the whole period of follow-up. Linear regression was performed on MBG values; HbA1c at 12 weeks, sex, age, body mass index (BMI) and patient status (Type 2 diabetes treated or not) were used as independent variables. None of the independent variables reached statistical significance in the model, with the exception of HbA1c at 12 weeks. The final model was: MBG (mg/dl) = (34.74 × HbA1c) , 79.21, r = 0.93; or MBG (mmol/l) = 1.91 × HbA1c , 4.36, r = 0.93. Conclusions Our results establish for the first time a strong correlation between MBG and HbA1c in Type 2 diabetic patients and support the idea of expressing HbA1c results as MBG. This will help patients to gain a clearer interpretation of the result, with less confusion. This simplification will allow every person with diabetes using home glucose-monitoring to understand his or her own target level. [source] Catheterization,Doppler Discrepancies in Nonsimultaneous Evaluations of Aortic StenosisECHOCARDIOGRAPHY, Issue 5 2005Payam Aghassi M.D. Prior validation studies have established that simultaneously measured catheter (cath) and Doppler mean pressure gradients (MPG) correlate closely in evaluation of aortic stenosis (AS). In clinical practice, however, cath and Doppler are rarely performed simultaneously; which may lead to discrepant results. Accordingly, our aim was to ascertain agreement between these methods and investigate factors associated with discrepant results. We reviewed findings in 100 consecutive evaluations for AS performed in 97 patients (mean age 72 ± 10 yr) in which cath and Doppler were performed within 6 weeks. We recorded MPG, aortic valve area (AVA), cardiac output, and ejection fraction (EF) by both methods. Aortic root diameter, left ventricular end-diastolic dimension (LVIDd) and posterior wall thickness (PWT) were measured by echocardiography and gender, heart rate, and heart rhythm were also recorded. An MPG discrepancy was defined as an intrapatient difference > 10 mmHg. Mean pressure gradients by cath and Doppler were 36 ± 22 mmHg and 37 ± 20 mmHg, respectively (P = 0.73). Linear regression showed good correlation (r = 0.82) between the techniques. An MPG discrepancy was found in 36 (36%) of 100 evaluations; in 19 (53%) of 36 evaluations MPG by Doppler was higher than cath, and in 17 (47%) of 36, it was lower. In 33 evaluations, EF differed by >10% between techniques. Linear regression analyses revealed that EF difference between studies was a significant predictor of MPG discrepancy (P = 0.004). Women had significantly higher MPG than men by both cath and Doppler (43 ± 25 mmHg versus 29 ± 15 mmHg [P = 0.001]; 42 ± 23 mmHg versus 32 ± 15 mmHg [P = 0.014], respectively). Women exhibited discrepant results in 23 (47%) of 49 evaluations versus 13 (25%) of 51 evaluations in men (P = 0.037). After adjustment for women's higher MPG, there was no statistically significant difference in MPG discrepancy between genders (P = 0.22). No significant interactions between MPG and aortic root diameter, relative wall thickness (RWT), heart rate, heart rhythm, cardiac output, and time interval between studies were found. In clinical practice, significant discrepancies in MPG were common when cath and Doppler are performed nonsimultaneously. No systematic bias was observed and Doppler results were as likely yield lower as higher MPGs than cath. EF difference was a significant predictor of discrepant MPG. Aortic root diameter, relative wall thickness, heart rate, heart rhythm, cardiac output, presence or severity of coronary artery disease, and time interval between studies were not predictors of discrepant results. [source] Bacterial traits, organism mass, and numerical abundance in the detrital soil food web of Dutch agricultural grasslandsECOLOGY LETTERS, Issue 1 2005Christian Mulder Abstract This paper compares responses to environmental stress of the ecophysiological traits of organisms in the detrital soil food webs of grasslands in the Netherlands, using the relationship between average body mass M and numerical abundance N. The microbial biomass and biodiversity of belowground fauna were measured in 110 grasslands on sand, 85 of them farmed under organic, conventional and intensive management. Bacterial cell volume and abundance and electrophoretic DNA bands as well as bacterial activity in the form of either metabolic quotient (qCO2) or microbial quotient (Cmic/Corg) predicted the response of microorganisms to stress. For soil fauna, the logarithm of body mass log(M) was approximately linearly related to the logarithm of numerical abundance log(N) with slope near ,1, and the regression slope and the proportion of predatory species were lower in intensive agroecosystems (more reduced substrates with higher energy content). Linear regression of log(N) on log(M) had slope not far from ,3/4. The approach to monitoring data illustrated in this paper could be useful in assessing land-use quality. [source] Extracellular phosphatase activity of natural plankton studied with ELF97 phosphate: fluorescence quantification and labelling kineticsENVIRONMENTAL MICROBIOLOGY, Issue 6 2003í Nedoma Summary ELF®97 phosphate (ELFP) is a phosphatase substrate which produces ELF®97 alcohol (ELFA), a fluorescent water-insoluble product, upon hydrolysis. We studied the kinetics of ELFA precipitation in freshwater samples at levels of total plankton and single phytoplankton cells, and tested the suitability of ELFP for measurement of surface-bound algal extracellular phosphatases. Samples from acidic Ple,né Lake (pH , 5; high phosphatase activity) and eutrophic ,ímov reservoir (pH ,7,10; moderate phosphatase activity) were incubated with ELFP for 5,300 min, fixed with HgCl2 and filtered through polycarbonate filters. Relative fluorescence of filter-retained ELFA precipitates was quantified with image analysis. Time-courses of ELFA formation exhibited lag periods followed by finite periods of linear increase. In Ple,né Lake, lag-times were shorter (1,18 min) and rates of increase in ELFA fluorescence higher (by ,2 orders of magnitude) than in ,ímov reservoir (lag-times 30,200 min). Similar patterns of ELFA formation kinetics were also observed in Ple,né Lake samples in cuvette spectrofluorometer measurements (which failed in ,ímov reservoir). Linear regression of seasonal data on rates of increase in ELFA fluorescence from image cytometry and spectrofluorometry (r2 = 0.65, n = 10) allowed for calibration of image cytometry in terms of amount of cell-associated ELFA. Preliminary measurements of extracellular phosphatase activities of several algae resulted in rates (10,2260 fmol cell,1 h,1) which are comparable to data reported in the literature for algal cultures. [source] Water Resource Implications of 18O and 2H Distributions in a Basalt Aquifer SystemGROUND WATER, Issue 6 2000Kathryn R. Larson Ongoing decline of water levels in the confined basalt aquifers of the Pullman-Moscow Basin of Washington and Idaho has prompted study of the timing, amount and distribution of recharge to the system. Previous radiocarbon ages indicate residence times on the order of 103 years and greater and suggest a low rate of recharge to the lower basalt aquifer since the end of Pleistocene time. By contrast, more recent hydrodynamic flow modeling studies invoke a larger Holocene recharge rate through the unconfined loess unit to the upper and lower basalt aquifers, which implies relatively short residence times (102 years). Stable isotopes were used to independently assess contrasting recharge models by comparing 18O/16O and D/H ratios of late-Holocene shallow ground water and deep ground water. Linear regression of local precipitation ratios yields ,D = 6.9 ,18O ,18.5. There is no evidence of fractionation of ground water ratios by recharge processes or water-rock interactions. Deep basalt ground water ,18O values are depleted by 0.4 to 4.9 per mil relative to shallow, recently recharged ground waters and have ,18O values statistically distinct from waters sampled from other stratigraphic units. These findings suggest that the deep waters in the basin were not precipitated under current climate conditions and that aquifer recharge rates to the deep basalt aquifer are substantially lower than have been recently estimated. This in turn suggests that a sustainable ground water exploitation scheme must reduce reliance on the deep ground water resource. [source] The Effect of Weather on HeadacheHEADACHE, Issue 6 2004Patricia B. Prince MD Objectives.,To assess headache patients' beliefs about how strongly weather affects their headaches; To objectively investigate the influence of multiple weather variables on headache. Design and Methods.,Our sample consisted of 77 migraineurs seen in a headache clinic, who provided headache calendars for a period ranging from 2 to 24 months. Our study was divided into two phases. First, each patient was given a questionnaire assessing their beliefs about how strongly (if so) weather affected their headaches. Second, weather data were collected from the National Weather Service, from three reporting stations central to the residences of the study participants. Analysis was performed on 43 variables to generate three meteorological factors. Linear regression was used to assess the relationship between headache and these three factors. Factor 1 represents a function of absolute temperature and humidity. Factor 2 represents a changing weather pattern. Factor 3 represents barometric pressure. Results.,Of the 77 subjects in the study, 39 (50.6%), were found to be sensitive to weather, but 48 (62.3%) thought they were sensitive to weather conditions (P < 0.05). Thirty (38.9%) were sensitive to one weather factor and 9 (11.7%) to two factors. Twenty-six (33.7%) were sensitive to factor 1; 11 (14.3%) to factor 2; 10 (12.9%) to factor 3. Conclusions.,Our study supports the influence of weather variables on headache. We showed that patients are susceptible to multiple weather variables and that more patients thought weather was a trigger than was the case. [source] Variation in Emergency Department Wait Times for Children by Race/Ethnicity and Payment SourceHEALTH SERVICES RESEARCH, Issue 6 2009Christine Y. Park Objective. To quantify the variation in emergency department (ED) wait times by patient race/ethnicity and payment source, and to divide the overall association into between- and within-hospital components. Data Source. 2005 and 2006 National Hospital Ambulatory Medical Care Surveys. Study Design. Linear regression was used to analyze the independent associations between race/ethnicity, payment source, and ED wait times in a pooled cross-sectional design. A hybrid fixed effects specification was used to measure the between- and within-hospital components. Data Extraction Methods. Data were limited to children under 16 years presenting at EDs. Principal Results. Unadjusted and adjusted ED wait times were significantly longer for non-Hispanic black and Hispanic children than for non-Hispanic white children. Children in EDs with higher shares of non-Hispanic black and Hispanic children waited longer. Moreover, Hispanic children waited 10.4 percent longer than non-Hispanic white children when treated at the same hospital. ED wait times for children did not vary significantly by payment source. Conclusions. There are sizable racial/ethnic differences in children's ED wait times that can be attributed to both the racial/ethnic mix of children in EDs and to differential treatment by race/ethnicity inside the ED. [source] Paraoxonase-1 (PON1) activity as a risk factor for atherosclerosis in chronic renal failure patientsHEMODIALYSIS INTERNATIONAL, Issue 4 2008Saeed Abdelwhab SAEED Abstract Paraoxonase is a high-density lipoprotein-associated enzyme and has been shown to reduce the susceptibility to low-density lipoprotein peroxidation. This study aimed to investigate the activity of serum paraoxonase in uremic patients on hemodialysis (HD) and in the predialysis period, and to evaluate the correlations of vascular disease with paraoxonase activity. Thirty patients with chronic renal failure (CRF) undergoing HD (group 1), 30 patients with CRF under conservative treatment (group 2), and 30 healthy controls (group 3) were included. Basal, salt-stimulated, and arylesterase activity were tested by UV spectrophotometry. Serum lipid parameters were determined. B-Mode Doppler ultrasound was used to assess common carotid intima-media thickness (IMT). Basal paraoxonase, salt-stimulated, and arylesterase activity showed no significant difference between group 1 and group 2. However, it was significantly lower in group 1 and in group 2 than controls. Carotid IMT was significantly higher in group 1 than group 2 and both were significantly higher than controls. Basal paraoxonase-1 (PON1), salt-stimulated PON1, and arylesterase activity correlate with BUN, but only basal PON1 and salt-stimulated PON1 correlate with serum albumin. Linear regression showed that the most significant determinant of carotid IMT was PON1 arylesterase activity in group 1 and arylesterase activity and basal PON1 activity in group 2. Patients with CRF, whether under HD or conservative treatment, have reduced basal and stimulated paraoxonase activities, and this could be an important factor causing increased vascular disease in those patients. Modifying this factor can be of great value to protect against this common complication. [source] Effects of sample and grid size on the accuracy and stability of regression-based snow interpolation methodsHYDROLOGICAL PROCESSES, Issue 14 2010J. Ignacio López Moreno Abstract This work analyses the responses of four regression-based interpolation methods for predicting snowpack distribution to changes in the number of data points (sample size) and resolution of the employed digital elevation model (DEM). For this purpose, we used data obtained from intensive and random sampling of snow depth (991 measurements) in a small catchment (6 km2) in the Pyrenees, Spain. Linear regression, classification trees, generalized additive models (GAMs), and a recent method based on a correction made by applying tree classification to GAM residuals were used to calculate snow-depth distribution based on terrain characteristics under different combinations of sample size and DEM spatial resolution (grid size). The application of a tree classification to GAM residuals yielded the highest accuracy scores and the most stable models. The other tested methods yielded scores with slightly lower accuracy and varying levels of robustness under different conditions of grid and sample size. The accuracy of the model predictions declined with decreasing resolution of DEMs and sample size; however, the sensitivities of the models to the number of data points showed threshold values, which has implications (when planning fieldwork) for optimizing the relation between the effort expended in gathering data and the quality of the results. Copyright © 2009 John Wiley & Sons, Ltd. [source] Transient storage and downstream solute transport in nested stream reaches affected by beaver damsHYDROLOGICAL PROCESSES, Issue 17 2009Li Jin Abstract Transient storage constitutes a key element in the hydrologic cycle of watersheds. Both in-channel slow moving water (dead zones) and hyporheic zones can contribute to transient storage, which retains water and solutes, increases residence time and influences solute transport in streams. Beaver dams and other in-stream obstructions throughout low-order streams attenuate streamflow and provide dead zone storage in pools. In this article, we report the results of four tracer tests in nested stream reaches in Cherry Creek (Wyoming, USA) covering ,2·5 km of stream length to explore how the degree of beaver dam obstructions and their impoundments influence water transient storage and downstream solute transport in low-order streams in the Rocky Mountain region of the American West. Travel-time parameters for the tracer tests increased linearly with beaver dam number (N) and pond size (V). Linear regression of the travel time to the peak concentration (Tp), the leading (Tl) and tailing edge (Tt) of the dye cloud and the duration of the dye cloud (Td) versus N and V were all significant (R2 = 0·99). Slopes of the linear regressions of Tt versus N and V, were three times larger than those for Tl, suggesting that longer residence times may be caused, in part, by transient storage in the stream system. One-dimensional transport with inflow and storage (OTIS) modelled cross-sectional area of transient storage zone (As) and dispersion coefficients (D) increased linearly with N and V and reach length. Two transient storage metrics, Fmean and , also showed a general increase with N and V, although the relationship was not as strong. This suggests that in-channel dead zones associated with beaver dams provide opportunities for generating transient water storage. The linear relationship between dispersion coefficient and reach length suggests the dispersion process might be analogous to the hydrodynamic dispersion in groundwater settings. Copyright © 2009 John Wiley & Sons, Ltd. [source] Covariabilities of spring soil moisture and summertime United States precipitation in a climate simulationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 4 2007Wanru Wu Abstract This paper explores the space-time connections between springtime soil moisture and summer precipitation over the continental United States by applying a singular value decomposition (SVD) method to a 50-year climate simulation. The first two SVD modes were analyzed. The two leading SVD modes account for 43% of the squared covariance between spring soil moisture and summer precipitation. Their corresponding components explain 14% of the soil moisture variance and 19% of the precipitation variance, respectively, which is larger than that contributed by tropical Pacific sea-surface temperatures (SSTs). The temporal correlations between the two expansion coefficients of each SVD mode are 0.83 and 0.88, respectively, indicating a significant association between spring soil moisture variation and summer precipitation variability. Both positive and negative cross-correlations exist over different regions of the United States in the two modes. Linear regression relates surface relative humidity and surface air temperature to the soil moisture SVD time series. The patterns revealed by the SVD analysis show where the local soil moisture-precipitation coupling contributes to the model's simulation of precipitation. Copyright © 2006 Royal Meteorological Society [source] Quality of life and depression of people living with type 2 diabetes mellitus and those at low and high risk for type 2 diabetes: findings from the Study to Help Improve Early evaluation and management of risk factors Leading to Diabetes (SHIELD)INTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 4 2008S. Grandy Summary Objectives:, This study compared health-related quality of life (HRQoL) and depression among individuals with type 2 diabetes mellitus (T2D) and those at low or high risk for T2D. Methods:, Respondents in a population-based US 2004 survey reported whether they had T2D (n = 3530) or risk factors for T2D [abdominal obesity, body mass index (BMI) , 28 kg/m2, dyslipidaemia, hypertension and history of cardiovascular disease]. Respondents without T2D were stratified into low risk (0,2 risk factors, n = 5335) and high risk (3,5 risk factors, n = 5051). SF-12 version 2 (SF-12) and Patient Health Questionnaire (PHQ)-9 were used to measure HRQoL and depression. Mean scores were compared across the three groups using analysis of variance. Linear regression identified factors associated with SF-12 Physical and Mental Component Summary scores (PCS and MCS), adjusting for age, gender, race, income, geographic region, household size, BMI and group. Results:, Respondents were mostly women (60%) with mean age of 54 years. Mean PCS scores for T2D and high risk (39.5 and 41.7, respectively) were significantly lower than for low risk (50.6, p < 0.001). After adjustment, high-risk and T2D groups were associated with lower PCS and MCS scores compared with low risk group (p < 0.05). Mean PHQ-9 scores and per cent with moderate-to-severe depression were significantly higher for T2D and high risk than for low risk (p < 0.01). Conclusions:, Health-related quality of life and depression scores in T2D were similar to those at high risk, and indicated significant decrements in physical health and greater depression compared with low-risk respondents. [source] Role of behavioural disturbance in the loss of autonomy for activities of daily living in Alzheimer patientsINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 11 2003L. Lechowski Abstract Background Cognitive impairment is associated with functional impairment in patients with Alzheimer's disease (AD). Behavioural disturbance is very common in these patients. Nevertheless, there has been very little research into the relations between behavioural disturbance and functional status in AD. The purpose of this study is to investigate the relationship between behavioural disturbance and functional status after taking account of cognitive impairment. Material and methods 579 patients were prospectively evaluated at 16 French hospitals, all referents for AD, and were diagnosed with possible or probable AD. These patients were assessed with NeuroPsychiatric Inventory (NPI), cognitive subscales of the Alzheimer's Disease Assessment Scale (ADAS-cog), Clinical Dementia Rating scale (CDR) and Instrumental Activities of Daily Living scale (IADL). Results The number of men with available data for IADL total score was too small to make any analysis. ,Group A' gathered 256 women for whom the relation between autonomy for Activities of Daily Living (ADL) and the other variables were determined. ,Group B', pooled 85 women for whom relations found were verified. Linear regression was used for the analysis. With age, cognitive impairment allows us to explain best (38%) the loss of autonomy for ADL. Conclusion The role of behavioural disturbances in the loss of autonomy for ADL was not determinant in our study, whereas cognitive impairment and age were better able to determine the loss of autonomy for ADL. Further study is needed to explain the decline of functional status in AD patients. Copyright © 2003 John Wiley & Sons, Ltd. [source] The Clinical Interview Schedule , Sinhala version: validation in a community setting in Sri LankaINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 4 2002Shiranee Champika Wickramasinghe Abstract The Clinical Interview Schedule , Revised (CIS-R) was validated in a clinic setting for adolescents 15,19 years of age in Sri Lanka. The interview schedule was translated into Sinhala and modified to include sections introducing each symptom group. One-hundred-and-thirty-one adolescents attending a psychiatric clinic for the first time were interviewed by a lay interviewer using CIS-R (Translated). They had previously been examined and rated by a psychiatrist using local (emic) diagnostic procedures. All the filtering questions showed a high level of sensitivity (80%,96%). None of the questions in the sleep problems and phobias sections were effective at discriminating between those who did and did not show significant symptoms in these areas according to the psychiatrist. The internal consistency of the sections of the interview schedule (when these two sections were excluded) varied between 0.60 and 0.82. Linear regression showed that, when both sections were excluded, 97% of the variation of total score could be explained. Therefore, it was decided to exclude the sleep problems and phobias sections from the modified interview schedule. As the population samples are likely to be different from clinic samples it is necessary to test the validity again in a community sample before confirming the validity of the modified interview schedule. Copyright © 2002 Whurr Publishers Ltd. [source] Serum Calcium and Cognitive Function in Old AgeJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 11 2007Miranda T. Schram PhD OBJECTIVES: To determine whether serum calcium is associated with cognitive function in elderly individuals in the general population. DESIGN: Prospective follow-up study of two independent, population-based cohorts. SETTING: The Rotterdam Study (median follow-up 11 years) and the Leiden 85-plus Study (median follow-up 5 years). PARTICIPANTS: Three thousand nine hundred ninety-four individuals, mean age 71, from the Rotterdam Study and 560 individuals, all aged 85, from the Leiden 85-plus Study. MEASUREMENTS: Global cognitive function was assessed in both cohorts using the Mini-Mental State Examination; attention, psychomotor speed, and memory function were assessed in the Leiden 85-plus Study only. Linear regression and linear mixed models were used for statistical analyses. RESULTS: In the Rotterdam Study, high serum calcium was associated with worse global cognitive function at baseline (P<.05) and a faster rate of decline in cognitive function during follow-up (P=.005) in individuals aged 75 and older but not in younger individuals. In the Leiden 85-plus Study, high serum calcium was associated with worse global cognitive function from age 85 through 90 (P<.001). This observation also held for the specific cognitive domains tested (all P<.01). These results did not change when individuals with serum calcium levels greater than normal (>2.55 mmol/L) were excluded from the analyses. CONCLUSION: In the general population, high serum calcium levels are associated with faster decline in cognitive function over the age of 75. [source] Homocysteine Level and Cognitive Function in Patients with Arterial Disease: The Second Manifestations of ARTerial Disease StudyJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 4 2006Fleur van A. Raamt MD OBJECTIVES: To assess the relationship between total plasma homocysteine (tHcy) level and cognitive function in patients with manifest arterial disease. DESIGN: Cross-sectional. SETTING: Patients with symptomatic cerebrovascular disease, cardiovascular disease, peripheral arterial disease, or abdominal aortic aneurysm included in the Second Manifestations of ARTerial disease study, a single-center, longitudinal study with an extensive screening program at baseline. PARTICIPANTS: Three hundred forty-five consecutively included patients, mean age 59. MEASUREMENTS: The patients underwent an extensive neuropsychological test. The cognitive domains assessed were memory, executive function, attention, and visuoperception and construction. Each raw score was transformed into standardized z-scores, and a sum score for global cognitive function was determined. Risk factors and vascular damage were measured in detail. RESULTS: Linear regression showed that elevated levels of tHcy were related to lower global cognitive function (,=,0.065, 95% confidence interval (CI)=,0.116 to ,0.013) and, more specifically, lower performance on memory (,=,0.078, 95% CI=,0.155 to ,0.002), attention (,=,0.079, 95% CI=,0.163 to ,0.005), and visuoperception and construction (,=,0.125, 95% CI=,0.236 to ,0.014) per standard deviation increase in tHcy (SD=6.4 mol/L), after adjustment for age, sex, educational level, extent of atherosclerosis, and location of vascular disease. Silent cerebral infarcts did not influence this relationship. CONCLUSION: A relationship was found between tHcy levels and cognitive function that was independent of extent and location of arterial disease. The results suggest that vascular mechanisms are not responsible for the relationship between tHcy and cognitive function. [source] Pneumonia: The Demented Patient's Best Friend?JOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 10 2002Discomfort After Starting or Withholding Antibiotic Treatment OBJECTIVES: To assess suffering in demented nursing home patients with pneumonia treated with antibiotics or without antibiotics. This study should provide the first empirical data on whether pneumonia is a "friend" or an "enemy" of demented patients and promote a debate on appropriate palliative care. DESIGN: Prospective cohort study. SETTING: Psychogeriatric wards of 61 nursing homes in the Netherlands. PARTICIPANTS: Six hundred sixty-two demented patients with pneumonia treated with (77%) or without (23%) antibiotics. MEASUREMENTS: Using an observational scale (Discomfort Scale,Dementia of Alzheimer Type), discomfort was assessed at the time of the pneumonia treatment decision and periodically thereafter for 3 months or until death. (Thirty-nine percent of patients treated with antibiotics and 93% of patients treated without antibiotics died within 3 months.) Physicians also offered a retrospective judgment of discomfort 2 weeks before the treatment decision. In addition, pneumonia symptoms were assessed at baseline and on follow-up. Linear regression was performed with discomfort shortly before death as an outcome. RESULTS: A peak in discomfort was observed at baseline. Compared with surviving patients treated with antibiotics, the level of discomfort was generally higher in patients in whom antibiotic treatment was withheld and in nonsurvivors. However, these same patients had more discomfort before the pneumonia. Breathing problems were most prominent. Shortly before death from pneumonia, discomfort increased. Discomfort was higher shortly before death when pneumonia was the final cause of death than with death from other causes. CONCLUSION: Irrespective of antibiotic treatment, pneumonia causes substantial suffering in demented patients. Adequate symptomatic treatment deserves priority attention. [source] Race/ethnicity and telomere length in the Multi-Ethnic Study of AtherosclerosisAGING CELL, Issue 3 2009Ana V. Diez Roux Summary Telomere length has emerged as a marker of exposure to oxidative stress and aging. Race/ethnic differences in telomere length have been infrequently investigated. Leukocyte telomere length (LTL) was assessed 981 white, black and Hispanic men and women aged 45,84 years participating in the Multi-Ethnic Study of Atherosclerosis. Direct measurement and questionnaire were used to assess covariates. Linear regression was used to estimate associations of LTL with race/ethnicity and age after adjustment for sex, income, education, smoking, physical activity, diet and body mass index. On average blacks and Hispanics had shorter telomeres than whites [adjusted mean differences (standard error) in T/S ratio compared to whites: ,0.041 (0.018) for blacks and ,0.044 (0.018) for Hispanics]. Blacks and Hispanics showed greater differences in telomere length associated with age than whites (adjusted mean differences in T/S ratio per 1 year increase in age ,0.0018, ,0.0047 and ,0.0055 in whites, blacks and Hispanics respectively). Differences in age associations were more pronounced and only statistically significant in women. Race/ethnic differences in LTL may reflect the cumulative burden of differential exposure to oxidative stress (and its predictors) over the lifecourse. [source] KINETICS AND HYDROLYSIS PARAMETERS OF TOTAL FRUCTOOLIGOSACCHARIDES OF ONION BULBS: EFFECTS OF TEMPERATURE REGIMES AND CULTIVARSJOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2007NOUREDDINE BENKEBLIA ABSTRACT This work studied the percentage of hydrolysis, observed hydrolysis rate constant (kobs), half-life time (t1/2) and kinetics of degradation of the total fructooligosaccharides (FOS) of three different onion bulb cultivars (Yellow Spanish, Red Amposta and Tenshin) kept during 6 months under three temperature regimes, 10, 15 and 20C. The percentage of hydrolysis of FOS was higher at 20C than at 10C and ranged from 47 to 58% at 10C, from 63 to 68% at 15C and from 74 to 83% at 20C. The kobs ranged from 27 × 10,3 to 36 × 10,3/week at 10C and from 41 × 10,3/week to 47 × 10,3/week at 15C, while at 20C, it was high and was about kobs 56 × 10,3/week.. The t1/2 decreased when temperature increased, and varied from 19.5 to 26.0 weeks at 10C, from 14.6 to 16.8 weeks at 15C and from 9.4 to 12.3 weeks at 20C, indicating that high degree of polymerization (DP) FOS have shorter lives than low DP FOS. Linear regression and kinetics of hydrolysis have shown that FOS hydrolysis is higher at 20C, with a coefficient of regression ranging between 0.87 and 0.99. Apparently, FOS hydrolysis is temperature independent, and storage time had more effect on the higher DP FOS than on the lower DP FOS. [source] Clinical course of chronic periodontitis: effect of lifelong light smoking (20 years) on loss of attachment and teethJOURNAL OF INVESTIGATIVE AND CLINICAL DENTISTRY, Issue 1 2010Marc Schätzle Abstract Aim:, To examine the lifelong effect of light smoking on periodontal health. Methods:, The data were derived from a 20-year longitudinal study of a group of Norwegian, middle-class males. The patients were subset according to their smoking history. A total of 119 non-smokers and 17 smokers were examined, 20 years apart. Results:, Current smokers had significantly higher plaque indices than non-smokers after the age of 35 years, while before 35 years, there was no difference. Before 20 years of age, the non-smokers exhibited greater gingival indices, but after the age of 35, the smokers had significantly more sites that bled upon probing. Smokers demonstrated higher mean calculus indices after 35 years and as they approached 50 years of age. At baseline, the two groups showed similar attachment loss (0.14 mm), but with increasing age and approaching 50 years, the attachment loss progressed significantly faster in smokers than in non-smokers (2.31 and 1.57 mm, respectively). Linear regression indicated that ageing and light smoking were independently and significantly related to attachment loss. Conclusions:, Lifelong light smoking could be confirmed as a risk factor for periodontal disease progression. However, in this population, smoking did not significantly increase the risk of tooth loss. [source] Nonweight-bearing anterior knee laxity is related to anterior tibial translation during transition from nonweight bearing to weight bearingJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2006Sandra J. Shultz Abstract We examined the relationship between anterior knee laxity (AKL), evaluated while the knee was nonweight bearing, and anterior translation of the tibia relative to the femur (ATT), evaluated when the knee transitioned from nonweight-bearing to weight-bearing conditions in response to an applied compressive load at the foot. Twenty subjects with normal knees (10 M, 10 F; 25.2,±,4.1 years, 169.8,±,11.5 cm, 71.6,±,16.9 kg) underwent measurements of AKL and ATT of the right knee on 2 days. AKL was measured at 133N with the KT-2000Ô. ATT was measured with the Vermont Knee Laxity Device and electromagnetic position sensors attached to the patella and the anteromedial aspect of the proximal tibia. Three trials for each measure were averaged and analyzed. Measurement consistency was high for both AKL (ICC,=,0.97; SEM,=,0.44 mm) and ATT (ICC,=,0.88; SEM,=,0.84 mm). Linear regression revealed that AKL predicted 35.5% of the variance in ATT (p,=,0.006), with a prediction equation of YATT,=,3.20,+,0.543(XAKL). Our findings suggest that increased AKL is associated with increased ATT as the knee transitions from nonweight-bearing to weight-bearing conditions. The potential for increased knee joint laxity to disrupt normal knee biomechanics during activities such as landing from a jump, or the foot strike phase of gait deserves further study. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:516,523, 2006 [source] COMLEX-1 and USMLE-1 Are Not Interchangeable ExaminationsACADEMIC EMERGENCY MEDICINE, Issue 2 2010John Sarko MD ACADEMIC EMERGENCY MEDICINE 2010; 17:1,3 © 2010 by the Society for Academic Emergency Medicine Abstract Objectives:, Osteopathic medical students must take the Comprehensive Osteopathic Medical Licensing Examination (COMLEX),USA series of examinations, but not the United States Medical Licensing Examination (USMLE-1) series. Few data are available describing the comparability of the two tests. This study sought to determine if COMLEX-1 scores could predict USMLE-1 scores among osteopathic medical students applying to an emergency medicine (EM) residency and to determine if the scores are interchangeable. Methods:, This was a retrospective analysis of osteopathic medical students applying to an EM residency program in the 2005,2006 and 2006,2007 application seasons. Students were included if they took both the COMLEX-1 and the USMLE-1 examinations. Linear regression was performed and a Bland-Altman plot of the standardized mean scores of each test was created. Results:, Ninety students were included. The mean (± standard deviation [SD]) COMLEX-1 score was 559.5 (±68.6), and the mean (±SD) USMLE-1 score was 207.6 (±15.5). The correlation was 0.79, with an R2 of 62.3%. The Bland-Altman plot showed a mean difference between the standardized scores of 0, with 95% confidence intervals (CIs) of ,1.28 to +1.28 standard normal units. Limitations include that this was a single center study, and only students who took both tests could be studied. Conclusions:, COMLEX-1 scores predict only 62.3% of the variance in USMLE-1 scores, and the scores are not interchangeable. [source] Usual sleep duration and cognitive function in older adults in SpainJOURNAL OF SLEEP RESEARCH, Issue 4 2009RAQUEL FAUBEL Summary The few studies that have examined the association between usual sleep duration and cognitive function have shown conflicting results. This cross-sectional study examined the association between sleep duration and cognitive function among 3212 people, representative of the non-institutionalized population aged 60 years and over in Spain. Sleep duration was self-reported, and cognitive function was measured with the Mini-Examen Cognoscitivo (MEC), a version of the Mini-Mental State Examination that has been validated in Spain. Linear regression, with adjustment for the main confounders, was used to obtain mean differences in the MEC between the categories of sleep duration (,5, 6, 7, 8, 9, 10, ,11 h day,1). The MEC score decreased progressively (became worse) across sleep categories from 7 to ,11 h (P for linear trend <0.001). People who slept for ,11 h had a significantly lower MEC score than those who slept for 7 h (mean difference ,1.48; 95% confidence interval ,2.12 to ,0.85). This difference in the MEC was similar to that observed for a 10-year increase in age. The results did not vary significantly by sex (P for interaction >0.05). No association was observed between short sleep duration (<7 h) and cognitive function. We conclude that long sleep duration is associated with poorer cognitive function in older adults from the general population. [source] Association of spinal cord compression seen on magnetic resonance imaging with clinical outcome in 67 dogs with thoracolumbar intervertebral disc extrusionJOURNAL OF SMALL ANIMAL PRACTICE, Issue 11 2006V. Penning Objectives: To determine whether there is an association between the degree of transverse spinal cord compression detected by magnetic resonance imaging following thoracolumbar Hansen type 1 intervertebral disc disease in dogs and their presenting and postsurgical neurological status. Methods: Medical records of 67 dogs with surgically confirmed Hansen type 1 intervertebral disc disease (2000 to 2004) were reviewed to obtain the rate of onset of disease, duration of clinical signs and presurgical and postsurgical neurological grade. Percentage of spinal cord compression was determined on transverse T2-weighted magnetic resonance images. Linear regression was used to examine the association between spinal cord compression and each of the above variables. Chi-squared tests were used to examine associations among postsurgical outcome and presurgical variables. Results: Eighty-five per cent (57 of 67) of dogs were chondrodystrophoid. Mean spinal cord compression was 53 per cent (sd=219·7, range 14·3 to 84·9 per cent). There was no association between the degree of spinal cord compression and the neurological grade at presentation, rate of onset of disease, duration of clinical signs or postsurgical outcome, with no difference between chondrodystrophoid and non-chondrodystrophoid dogs. Clinical Significance: The degree of spinal cord compression documented with magnetic resonance imaging in dogs with thoracolumbar Hansen type 1 intervertebral disc disease was not associated with the severity of neurological signs and was not a prognostic indicator in this study. [source] | |||||||||||||||||||||||||||||||||||||||||||