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Results for “multiple linear regression”

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PubMed2001

Plasma leptin is independently associated with the intima-media thickness of the common carotid artery.

OBJECTIVE: To investigate whether intima-media thickness (IMT) of the common carotid artery (CCA), an early marker of asymptomatic atherosclerosis, is significantly and independently associated with plasma concentrations of leptin, an adipose tissue hormone that has recently been proposed as a cardiovascular risk factor in obese patients. DESIGN: Cross-sectional sample of normal-weight and obese men and women. SUBJECTS: One-hundred and twenty healthy subjects (52 men and 68 women), aged 18-45 y and with a wide range of BMI, were recruited for the study. MEASUREMENTS: Fasting plasma leptin concentrations and the IMT of the CCA were measured in all subjects. Leptin concentrations were measured by radioimmunoassay and the IMT of the CCA was quantified by high resolution B-mode ultrasound imaging. Central fat (measured by waist circumference), smoking habits, blood pressure, insulin sensitivity (measured by the insulin tolerance test), and fasting plasma glucose, insulin and lipid pattern (cholesterol, HDL-cholesterol, triglycerides, LDL-cholesterol) were also measured. RESULTS: IMT of the CCA was positively correlated with log leptin concentrations (P<0.005 in men and P<0.001 in women), body mass index (P<0.001 in men and women), waist circumference (P<0.001 in men and women), age (P<0.001 in men and P<0.05 in women), and negatively associated with insulin sensitivity in both sexes (P<0.05). IMT was also directly correlated with cholesterol (P<0.05), LDL-cholesterol (P<0.01) and systolic blood pressure in men (P<0.05), and with diastolic blood pressure levels in women (P<0.05). When a multiple linear regression model was used without body mass index (BMI), the correlation between leptin and IMT was maintained in both men (P<0.01) and women (P<0.005), independent of age, insulin sensitivity, smoking habits, systolic blood pressure, fasting glucose, triglycerides, cholesterol, LDL-cholesterol and HDL-cholesterol. By contrast, BMI-adjusted leptin concentrations were not significantly associated with IMT (Pc (partial correlation): 0.41 in men and 0.15 in women). Moreover, when BMI was entered into a multiple linear regression model without leptin, the correlation between BMI and IMT was maintained in both men (P<0.005) and women (P<0.01), independent of the same parameters. CONCLUSION: Plasma leptin concentrations are independently associated with the IMT of the CCA, suggesting that the increase of adipose tissue mass (or leptin per se) may have an unfavourable influence on the development of atherosclerosis. However, the association between IMT and leptin seems to be dependent and/or confounded by the relationship between IMT and obesity.

Adipose Tissue↗

PubMed2005

Variation in precaecal amino acid and energy digestibility between pea (Pisum sativum) cultivars determined using a linear regression approach.

An experiment was conducted to study the variation in the precaecal amino acid (AA) and energy digestibility of 4 cultivars of white-flowering peas (Pisum sativum) for broiler chickens. The 4 cultivars were grown and harvested under the same agronomic and environmental conditions. One basal diet and 8 diets including each pea cultivar at inclusion rates of either 150 or 300 g/kg were used. Peas were included at the expense of starch. Hence, the differences in dietary crude protein and AA concentrations resulted only from the inclusion of peas. Titanium dioxide was included as an indigestible marker. Crude protein concentrations in the complete diets ranged from 164 to 244 g/kg. All diets were fed ad libitum to broiler chickens between 14 and 21 d of age. Seven pens of 12 chickens were allocated to each treatment. Digesta were sampled on a pen basis from the section of the gastrointestinal tract between Meckel's diverticulum and 2 cm anterior to the ileo-caeco-colonic junction. The proportions of crude protein and AAs digested responded linearly to increased intake and the relationships between quantitative intake and digested amounts of AAs were described by multiple linear regressions. The slope determined for each pea cultivar was taken as a measure of AA digestibility without the need for consideration of basal endogenous crude protein and AA secretions. Digestibility of AAs in peas ranged from 0.60 to 0.91. One cultivar had significantly lower AA digestibilities than the other three cultivars. This could be explained neither by the trypsin inhibitor activity nor by tannin levels. The AAs with the highest digestibilities in all cultivars were arginine > glutamic acid > lysine > methionine > phenylalanine > leucine. The AAs with the consistently lowest digestibilities were cystine < threonine. The ranking of the remaining AAs varied slightly between cultivars. The multiple linear regression approach is suitable to study differences in AA digestibilities without the need for consideration of basal endogenous AA losses. Diets containing 300 g/kg of peas had significantly lower energy digestibilities than the pea-free basal diet. The pea cultivar with the lowest AA digestibility caused the lowest energy digestibility at both levels of pea inclusion.

Amino Acids↗

PubMed2003

Determinants of handgrip strength in free-living elderly at risk of malnutrition.

PURPOSE: Handgrip strength is necessary for performing activities of daily living, which, in turn, are required to maintain functional autonomy. The purpose of this study was to determine anthropometric and personal factors that affect handgrip strength in a group of free-living elderly at risk of malnutrition. METHOD: The factors associated with handgrip strength (Pearson r, t-test, alpha = 0.10) were entered in a multiple linear regression model (n = 166) to identify the independent prediction factors. Reliability of the model was verified with a sub-group of 65 subjects randomly selected from the initial sample. RESULTS: Both groups were statistically similar regarding all factors studied even though the validation group (n = 65) had more men (32%) compared to the development group (n = 166; 22%). Bivariate analyses showed that handgrip strength was associated with sex, age, pain, hand circumference, and waist-hip ratio. Multiple linear regression analysis identified age, pain, and sex as independent determinants of handgrip strength (R2 = 0.16). This model predicted handgrip strength better in the validation group (R2 = 0.29). CONCLUSIONS: As previously shown, women have a smaller handgrip strength than men. In addition, handgrip strength decreases with increasing age and the presence of pain. Emphasis should be placed on the importance of strategies to relieve pain in the free-living frail elderly population.

Activities of Daily Living↗

PubMed2004

Associations between body-mass index and surgery for rotator cuff tendinitis.

BACKGROUND: Rotator cuff tendinopathy is a common entity. We hypothesized that obesity, because of biomechanical and systemic risk factors, increases the risks of rotator cuff tendinitis, tears, and related surgical procedures. METHODS: A frequency-matched case-control study was conducted. Three hundred and eleven patients who were fifty-three to seventy-seven years old and who underwent rotator cuff repair, arthroscopy, and/or other repair of the shoulder in a large hospital from 1992 to 2000 were included in the study. These surgical procedures were used as proxies for the risk of rotator cuff tendinitis. These patients were age and frequency-matched to 933 controls, who were randomly drawn from a pool of 10,943 potential controls consisting of Utah state residents who were enrolled in a large cancer-screening trial. Age-adjusted odds ratios were calculated with use of the International Classification of Diseases, Ninth Revision procedural codes and body-mass-index groups. The data were stratified according to gender and age. Multiple linear regression analyses also were performed. RESULTS: There was an association between increasing body-mass index and shoulder repair surgery. The highest odds ratios for both men (odds ratio = 3.13; 95% confidence interval = 1.29 to 7.61) and women (odds ratio = 3.51; 95% confidence interval = 1.80 to 6.85) were for individuals with a body-mass index of > or =35.0 kg/m(2). Tests for trend also were highly significant for both men (p = 0.002) and women (p < or = 0.001). Multiple linear regression analysis also indicated a significant association between increasing body-mass index and shoulder surgery (beta = 1.57; 95% confidence interval = 0.97 to 2.17; p < or = 0.001). CONCLUSIONS: There is an association between obesity and shoulder repair surgery in men and women who are fifty-three to seventy-seven years of age. The results of the present study suggest that increasing body-mass index is a risk factor for rotator cuff tendinitis and related conditions.

Aged↗

PubMed2000

Percent body fat and bone mass in healthy Canadian females 10 to 19 years of age.

The primary aim of the investigation was to assess the relationship between whole-body fat expressed as a percentage of body weight with whole-body bone mineral content relative to age and anthropometry. Sixty females between 10 and 19 years of age were recruited to this cross-sectional study, which included measurements of weight and height and whole-body fat and bone mineral content using dual-energy X-ray absorptiometry. To assess bone mineral content, data were expressed as a weight or standard deviation scores using age and bone area. Relationships between outcome variables were determined using multiple correlation analysis followed by multiple linear regression with age, weight, height, and fat as predictor variables for outcomes of bone mineral content and density. Correlation analysis indicated that whole-body fat expressed as a percent was significantly related to weight (p < 0.01), but was not related to age or bone mineral content or density unless bone mineral content was corrected to age or bone area using standard deviation scores. In addition, body fat was associated with bone area for age and height (p < 0.01). However, multiple linear regression yielded opposite results. When included in regression, body fat had a negative impact on bone mineral content (p = 0.003), mineral content corrected to bone area (p = 0.02), and bone density (p = 0.003), while age, weight, and height had positive impacts on these outcome measurements. The data suggest that for younger children, the relative influence of percent body fat will be greater and could be linked with suboptimal attainment of peak bone mass. The females in this study appeared to be within reference limits for percent body fat. However, greater amounts of body fat relative to weight could be a marker for lifestyles that do not support attainment of optimal peak bone mass.

Absorptiometry, Photon↗

PubMed2000

Body composition and resting energy expenditure in humans: role of fat, fat-free mass and extracellular fluid.

OBJECTIVE: The objective of this study was to determine whether there are independent effects of extracellular fluid volume (ECF) and fat mass (FM) on resting energy expenditure (REE) relative to fat-free mass (FFM) in adult men and women. METHODS: Multiple linear regression analysis was used to relate REE, as determined by indirect calorimetry, to FFM and FM (measured using dual energy X-ray absorptiometry) and ECF (measured using bromide space and/or the radiosulfate washout space) in 153 women and 100 men with varying amounts of body fat. RESULTS: REE correlated significantly with FFM and FM in women (r=0.65 and r=0.63, both P<0.001) and men (r=0.62 and r=0.48, both P<0.001, FFM and FM, respectively). In a multiple linear regression analysis FFM, FM and age significantly contributed to the ability to predict REE in both genders. The models that were derived were not significantly different between women and men. In women the contribution to REE from FM was easier to detect when FM was greater. Adjustment of FFM for ECF did not improve the relationship between FFM and REE. CONCLUSIONS: FFM, FM and age are significant, independent predictors of REE in both men and women. Adjustment of FFM for ECF does not improve the ability of FFM to predict REE, which suggests that ECF is a highly integrated component of FFM in healthy adults. Expressing REE relative to FFM alone will introduce errors when lean and obese populations are compared.

Absorptiometry, Photon↗

PubMed2006

Analysis and prediction of flow from local source in a river basin using a Neuro-fuzzy modeling tool.

Traditionally, the multiple linear regression technique has been one of the most widely used models in simulating hydrological time series. However, when the nonlinear phenomenon is significant, the multiple linear will fail to develop an appropriate predictive model. Recently, neuro-fuzzy systems have gained much popularity for calibrating the nonlinear relationships. This study evaluated the potential of a neuro-fuzzy system as an alternative to the traditional statistical regression technique for the purpose of predicting flow from a local source in a river basin. The effectiveness of the proposed identification technique was demonstrated through a simulation study of the river flow time series of the Citarum River in Indonesia. Furthermore, in order to provide the uncertainty associated with the estimation of river flow, a Monte Carlo simulation was performed. As a comparison, a multiple linear regression analysis that was being used by the Citarum River Authority was also examined using various statistical indices. The simulation results using 95% confidence intervals indicated that the neuro-fuzzy model consistently underestimated the magnitude of high flow while the low and medium flow magnitudes were estimated closer to the observed data. The comparison of the prediction accuracy of the neuro-fuzzy and linear regression methods indicated that the neuro-fuzzy approach was more accurate in predicting river flow dynamics. The neuro-fuzzy model was able to improve the root mean square error (RMSE) and mean absolute percentage error (MAPE) values of the multiple linear regression forecasts by about 13.52% and 10.73%, respectively. Considering its simplicity and efficiency, the neuro-fuzzy model is recommended as an alternative tool for modeling of flow dynamics in the study area.

Forecasting↗

PubMed1997

Cytomegalovirus disease is associated with increased cost and hospital length of stay among orthotopic liver transplant recipients.

Cytomegalovirus (CMV) is a cause of considerable morbidity and mortality among orthotopic liver transplant (OLT) recipients. To study the impact of CMV on cost and hospital length of stay in this population, we undertook an analysis of a cohort of OLT recipients from four transplant centers in Boston who participated in a CMV prophylaxis trial. First posttransplant year hospital length of stay (including the hospital stay after transplantation and readmissions within 1 year after transplantation) was available for all 141 patients included in the study. In a multiple linear regression model bacteremia (P=0.0001), CMV disease (P=0.0007), abdominal reexploration (excluding retransplantation) (P=0.0070), recipient age < or = 16 years (P=0.0352), and the number of units of blood products (red blood cells, platelets, or fresh frozen plasma) administered during transplantation (P=0.0523) were shown to be independently associated with longer first posttransplant year hospital length of stay. Cost data for in-hospital care for the year beginning with admission for liver transplantation were available for 66 OLT recipients. Using a multiple linear regression model, development of CMV disease (P=0.0001), the number of units of blood products administered during transplantation (P=0.0001), bacteremia (P=0.0002), decreased pretransplant renal function (estimated by creatinine clearance) (P=0.0109), and need for retransplantation (P=0.0619) were shown to be independently associated with higher cost. These data strongly suggest that CMV disease has a direct impact on cost and hospital length of stay in liver transplantation.

Adolescent↗

PubMed2006

Postoperative nausea and vomiting following inpatient surgeries in a teaching hospital: a retrospective database analysis.

OBJECTIVE: To report the incidence of postoperative nausea and vomiting (PONV), to describe the use of anti-emetics both for the prophylaxis and treatment of PONV, and to assess resource utilization and duration of post-anesthesia care unit (PACU) stay. RESEARCH DESIGN AND METHODS: We retrieved data from the Duke Anesthesia Peri-operative database. We included adult patients, who underwent inpatient surgery under general anesthesia with inhaled agents between January 2004 and February 2005, and had two or more risk factors for PONV documented preoperatively (female, previous history of PONV or motion sickness, non-smoker or use of postoperative opioid). Data on the use of prophylactic anti-emetics, the incidence of PONV, nausea scores, pain scores, and the use of rescue anti-emetics in PACU and in the period between PACU discharge and 24 h after surgery were recorded. Resource utilization and cost assessment was performed from the perspective of the hospital and included length and direct cost of PACU stay, as well as the acquisition costs of rescue anti-emetics in PACU. Descriptive statistics were used to summarize the demographic characteristics of patients. For group comparisons, data were analyzed with the t-test for continuous data, and the Chi-square test for categorical data. Multiple linear regression models were used to evaluate the association between PONV and PACU length of stay adjusting for confounding factors. RESULTS: A total of 3641 patients were included in the analysis. Of those, 2869 (79%) received prophylactic anti-emetics. In the PACU, nausea and vomiting were reported in 16% and 3% of the patients, respectively. Rescue anti-emetics were given to 26% of all patients. The incidence of vomiting was significantly less in patients who received PONV prophylaxis (p = 0.03). In multiple linear regression models, the duration of PACU stay was longer by a mean of 25 min in patients who experienced PONV or received rescue anti-emetics in PACU (p < 0.0001) despite the fact that the duration of surgery was shorter by a mean of 24 min in this group of patients (p < 0.0001). Following PACU discharge, 40% of patients reported nausea, vomiting or needed rescue anti-emetics. PONV was associated with significantly increased resource utilization and costs of PACU stay (p < 0.0001). Emesis was associated with greater incremental cost (138 US dollars) than nausea (85 US dollars), mainly from the longer duration of PACU stay. CONCLUSIONS: PONV remain a significant problem postoperatively and often persists beyond PACU discharge. The presence of PONV is associated with increased length of PACU stay and greater resource utilization and costs.

Adult↗

PubMed1995

Comparison of the effects of hydrophobicity, amphiphilicity, and alpha-helicity on the activities of antimicrobial peptides.

Multiple linear regression was used to quantify the dependence of the antimicrobial activity of 13 peptides upon three calculated or experimentally determined parameters: mean hydrophobicity, mean hydrophobic moment, and alpha-helix content. Mean hydrophobic moment is a measure of the amphiphilicity of peptides in an alpha-helical conformation. Antimicrobial activity was quantified as the reciprocal of the measured minimal inhibitory concentration (MIC) against Escherichia coli. One of the peptides was magainin 2, and the remainder were novel peptides designed for this study. The multiple linear regression results revealed that the amphiphilicity of the peptides was the most important factor governing antimicrobial activity compared to mean hydrophobicity or alpha-helix content. A better regression of the data was obtained using ln(1/MIC+constant) as the dependent variable than with either 1/MIC or ln(1/MIC). These results should be useful in designing peptides with higher antimicrobial activity.

Amino Acid Sequence↗

PubMed1998

Reproducibility and validity of the assessment of clinical furcation parameters as related to different probes.

The aim of this study was to investigate the reliability of the assessment of clinical furcation parameters (horizontal attachment levels [CAL-H], class of furcation invasion). Replicate measurements of CAL-H and furcation class were performed within 14 days in 420 molars of 105 patients with advanced periodontitis using a Nabers- (n=50), a TPS- (n=30) and a PCPUNC15-probe (n=25). Validity of clinical assessments was assessed by intrasurgical measurements. The standard deviation of single measurements (s) was calculated as a measure of the reproducibility of CAL-H measurements and weighted kappa-coefficients (Kw) to estimate the agreement of furcation class assessments. The s ranged from 0.55 to 1.13 mm (Nabers), 0.55 to 1.02 mm (TPS), and 0.58 to 1.11 mm (PCPUNC15). For all probes, a statistically significantly smaller measurement error was observed in buccal and lingual sites than in mesiolingual and distolingual furcations (P < 0.005). The Kw ranged from 0.59 to 0.89 (Nabers), 0.50 to 0.80 (TPS), and 0.53 to 0.72 (PCPUNC 15). Multiple linear regression analysis identified distolingual location, probing depth (PD) and CAL-H as factors influencing the variability of CAL-H measurements. Whereas there was no statistically significant difference between pre- and intrasurgical CAL-H measurements using the Nabers probe, the TPS and PCPUNC15 probe underestimated CAL-H for distolingual furcations (P < 0.025). Using the Nabers probe, no asymmetries between pre- and intrasurgically obtained class of furcation involvement were revealed, while the TPS and PCPUNC15 probe underestimated furcation degrees (P < 0.1). Multiple linear regression analysis identified distolingual location and height of furcation, as well as PD, vertical attachment level (CAL-V) and type of probe, as factors influencing the validity of CAL-H measurements. Clinical diagnosis of furcation lesions using the 3 mm incrementally marked Nabers probe provides reproducible and valid information about furcation invasion.

Adult↗

PubMed2005

Removal of pesticides from aqueous solution: Quantitative relationship between activated carbon characteristics and adsorption properties.

The adsorption of pesticides (atrazin, atrazin-desethyl and triflusulfuron-methyl) from aqueous solution is performed by activated carbon fibers (ACF) and granular activated carbons (GAC) in static and dynamic reactors, in order to study the co-influence of adsorbent and adsorbate characteristics on the adsorption mechanisms. First, mono-component adsorption equilibrium is carried out in a batch reactor for a wide range of concentrations (from 5 microg 1(-1) to 21.4 mg 1(-1)). Classic models, like Freundlich and Langmuir equations, are applied: the maximum adsorption capacities are high, ranging between 63 and 509 mg g(-1). The comparison of single-solute isotherms tends to confirm the decisive role of the adsorbent properties in the adsorption capacity of pesticides by the activated carbons: the performance of ACF is significantly higher than that of GAC due to a narrower pore size distribution of fibers in the area of micropores. Furthermore, their small diameter (10 microm compared with 1 mm for grains) enables faster adsorption kinetics because of the larger surface area exposed to the fluid. The influence of adsorbate size is also demonstrated. A multiple linear regression enables the co-influence of adsorbent and adsorbate properties to be quantified, a relationship being assessed between Langmuir maximum adsorption capacity and pesticide molecular weight and adsorbent diameter (R2 = 0.90). Secondly, the adsorption of the three pesticides is studied in a dynamic reactor: in this case, the influence of operating conditions (inlet concentration C0, flow velocity U0) is also taken into account. As the initial concentration or flow velocity decreases, the column performance significantly improves. Both operating factors are included in a multiple linear regression (R2 = 0.91) used to predict saturation adsorption capacity, with molecular weight and particle diameter being again designed as influent explicative variables.

Adsorption↗

PubMed1994

[Epidemiology of emphysema: analysis by autopsy in a series of elderly patients].

Epidemiologic studies indicate that various factors are involved in causing emphysema, although it is uncertain exactly how these factors contribute. Thus the correlation between pathological changes and clinical manifestations was studied. Results of autopsies done on 1940 men and 1791 women from 1978 to 1992 were analyzed retrospectively. Emphysema was graded, from macroscopic findings as follows: none (E 0), slight (E 1), moderate (E 2), and severe (E 3). The severity of anthracocsis was graded as well. Information regarding clinical diagnosis, smoking habits, and available spirometric data were obtained by reviewing the medical records. Prevalence of each grade of emphysema was: in men, E 0-48.6%, E 1-31.6%, E 2-15.8%, and E 3-4.0%; in women, E 0-81.6%, E 1-13.7%, E 2-3.7%, and E 3-0.8%. Pneumonia, lung cancer, and gastric ulcer were significant complications of emphysema, and may have contributed to the cause of death. The effects of various risk factors on the severity of emphysema were evaluated by multiple linear regression analysis. Male sex, age, smoking habit, and grade of the anthracosis were independent factors affecting the development of emphysema. Among them, anthracosis grade and smoking habit were found to be strongly contributing factors. Emphysema grade and FEV1% were significantly correlated, but several patients with moderate or severe emphysema did not show airflow obstruction. Therefore, receiver operating characteristic (ROC) curves were constructed to evaluate the value of the FEV1% in the diagnosis of emphysema. The diagnostic value of the FEV1% alone was low, so a multiple linear regression equation with three factors (sex, smoking habit, and FEV1%) was constructed.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed2006

Elbow capsulectomy for posttraumatic elbow stiffness.

PURPOSE: To determine factors associated with diminished elbow function and upper-extremity-specific health status after elbow capsulectomy for posttraumatic stiffness. METHODS: Forty-six adult patients with posttraumatic elbow stiffness were evaluated an average of 48 months after open capsular excision. A second capsular excision was performed in 9 patients (29%). Stepwise multiple linear regression analysis was used to identify predictors of the American Shoulder and Elbow Surgeons Elbow Score, the Mayo Elbow Performance Index, and the Disabilities of the Arm, Shoulder, and Hand scores after all procedures. RESULTS: The average improvement in ulnohumeral motion after the index surgery for capsular release was 53 degrees . (The average flexion was 98 degrees .) The 9 patients who had subsequent repeat elbow contracture release gained an additional 24 degrees , leading to a final average flexion arc for the entire cohort of 103 degrees . Multiple linear regression identified the American Shoulder and Elbow Surgeons pain score, persistent ulnar nerve dysfunction, and duration of follow-up evaluation after the initial capsular release as independent predictors of a higher Disabilities of the Arm, Shoulder, and Hand questionnaire score; flexion arc and pain score as independent predictors of the Mayo Elbow Performance Index; and flexion arc, forearm arc, pain score, and persistent ulnar neuropathy as independent predictors of the American Shoulder and Elbow Surgeons score. CONCLUSIONS: Open elbow capsulectomy for posttraumatic elbow stiffness restores a near-100 degrees flexion arc on average. Second elbow releases provide limited additional motion in most patients. Final motion influences physician-based rating scales but not patient-specific health status (Disabilities of the Arm, Shoulder, and Hand questionnaire), which is dominated by pain and persistent ulnar neuropathy. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Adolescent↗

PubMed2001

Marker pair selection for mapping quantitative trait loci.

Mapping of quantitative trait loci (QTL) for backcross and F(2) populations may be set up as a multiple linear regression problem, where marker types are the regressor variables. It has been shown previously that flanking markers absorb all information on isolated QTL. Therefore, selection of pairs of markers flanking QTL is useful as a direct approach to QTL detection. Alternatively, selected pairs of flanking markers can be used as cofactors in composite interval mapping (CIM). Overfitting is a serious problem, especially if the number of regressor variables is large. We suggest a procedure denoted as marker pair selection (MPS) that uses model selection criteria for multiple linear regression. Markers enter the model in pairs, which reduces the number of models to be considered, thus alleviating the problem of overfitting and increasing the chances of detecting QTL. MPS entails an exhaustive search per chromosome to maximize the chance of finding the best-fitting models. A simulation study is conducted to study the merits of different model selection criteria for MPS. On the basis of our results, we recommend the Schwarz Bayesian criterion (SBC) for use in practice.

Chromosome Mapping↗

PubMed2006

Obesity is negatively associated with prostate-specific antigen in U.S. men, 2001-2004.

BACKGROUND: Recent studies have shown a negative association between body mass index (BMI) and prostate-specific antigen (PSA), a commonly used serum marker for the detection and diagnosis of prostate cancer. We have examined the association between several anthropometric measures and PSA in a nationally representative sample of men. METHODS: We analyzed data from the 2001-2004 National Health and Nutrition Examination Survey. Participants in this study were men ages >or=40 years without previously diagnosed prostate cancer who had PSA measured. Height, weight, waist circumference, BMI, triceps skinfold, subscapular skinfold, and calculated total body water were examined categorically by quintiles using multiple linear regression models. All tests of significance were two sided. RESULTS: Among white men, we report a trend for decreasing PSA with increasing weight, BMI, waist circumference, triceps skinfold thickness, and calculated total body water. Among Mexican American men, we found a trend for decreasing PSA with increasing BMI, and among black men we found a trend for decreasing PSA with increasing triceps thickness. None of the interaction terms between race/ethnicity and any of the anthropometric measures were statistically significant. Controlling for age and race/ethnicity in the multiple linear regression model, we found moderate declines in PSA with a 1 SD increase in BMI [5.9% decrease (95% confidence interval, -9.0% to -2.8%) in geometric mean PSA per 5.2-unit increase], weight [5.9% decline (-8.8% to -2.8%) per 17.7-kg increase], waist circumference [6.6% decline (-9.4% to -3.6%) per 13.4-cm increase], triceps skinfold [5.4% decline (-8.9% to -1.8%) per 6.4-mm increase], and calculated total body water [5.7% decline (-8.9% to -2.4%) per 6.5-liter increase]. CONCLUSION: Our population-based, nationally representative results expand the validity of previous studies on obesity and PSA. Higher weight, BMI, waist circumference, triceps skinfold, and total body water are associated with moderately lower PSA values. A prospective study is needed to verify whether this association affects the accuracy of the PSA test in obese men.

Humans↗

PubMedDate not supplied

Time-related trends of age at menopause and reproductive period of women in a Chuvashian rural population.

OBJECTIVE: The objective of this study was to examine in an observational, cross-sectional, community-based study the secular trend of age at menopause among women in a rural Chuvashian population and to identify factors associated with age at menopause. DESIGN: The sample included 316 postmenopausal women born between 1920 and 1950 with mean age at menopause of 48.47 +/- 4.63 (34-58) years. Statistical analyses included simple and multiple linear regression and "whiskers" plots. RESULTS: Significant association was found between year of birth and age at menopause (beta = 0.194, P < 0.001) and reproduction period (P = 0.193, P < 0.001). Mean values of age at menopause increased from 47.0 years (born during 1920-1925) to maximal values of 49.7 years (born during 1940-1945) and 49.3 years (born during 1945-1950). Mean values of their reproductive period increased from 30.7 (born during 1920-1925) to maximal values of 34.1 (born during 1940-1945) and to 33.7 (born during 1945-1950). Multiple linear regression analysis demonstrated that year of birth was the only statistically significant (P = 0.19, P < 0.01) predictor of age at menopause. Age at menarche can also be a possible predictor of age at menopause (beta = -0.12, P = 0.04). CONCLUSIONS: The study confirmed certain secular trends of age at menopause and reproductive periods in Chuvashian women. The authors also observed a negative association between age at menarche and age at menopause. The number of children and medical abortions as well as body mass index showed no association with age at menopause.

Adult↗

PubMed2004

Reversal of P-glycoprotein mediated vincristine resistance of L1210/VCR cells by analogues of pentoxifylline. A QSAR study.

In our previous papers we described the ability of methylxanthine pentoxifylline (PTX) to depress the P-glycoprotein (P-gp) mediated multidrug resistance (MDR) of the mouse leukemic cell line L1210/VCR. Other methylxanthines like caffeine and theophylline were found to be ineffective in this respect. In the present paper we have analysed the capability of 25 methylxanthines to depress MDR of L1210/VCR cells. These methylxanthines structurally differ in substituents located in positions N1, N3, N7 and C8. The results indicate that for an effective reversal of P-gp mediated MDR of our cells the existence of a longer polar substituent in the position N1 plays a crucial role. The elongation of the substituent in the positions N3 and N7 (from methyl to propyl) increases and in the position C8 (from H to propyl) decreases the efficacy of xanthines to reverse the vincristine resistance of L1210/VCR cells. The multiple linear regression for effectiveness of methylxanthines in reversal of P-gp mediated MDR of L1210/VCR cells (expressed as respective IC(50r) values) has been computed, with molar weight: M(w), molar volume: V(M), molar refractivity: R(M), crystal density: d and partition coefficient n-octanol/water: logP as descriptors. A high intercorrelation of M(W), V(M) and R(M) was found for the tested group of methylxanthines indicating that only one of these parameters is necessary for testing a potential correlation. The best fit in the multiple linear regression was obtained for R(M) applied together with d and logP and resulted in a QSAR model given by the following equation: IC(50r)=-[(32.3+/-7.2)x10(-3)xR(M)]+[(10.1+/-2.3)xd]+[(0.74+/-0.10)xlogP]-[10.5+/-3.2]. Model revealed that: (i) the molar refractivity influences the effectiveness of xanthine positively; (ii) the crystal density and partition coefficient influence the MDR reversal effectiveness of xanthine negatively.

ATP Binding Cassette Transporter, Subfamily B, Mem↗