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PubMed2006

Association of vascular risk factors with increasing glycemia even in normoglycemic subjects in an older Chinese population: the Guangzhou Biobank Cohort Study.

Hyperglycemia increases cardiovascular disease risk, but the association between increasing glycemia and cardiovascular risk factors, angina, and coronary heart disease in normoglycemic subjects is less clear, particularly in Chinese. We report on possible associations in a large group of Mainland Chinese subjects. A total of 10,400 older subjects (> or = 50 years) were recruited, and vascular risk factors were measured, including anthropometry, blood pressure, and fasting plasma biochemical factors including glucose, lipid profile, and C-reactive protein (CRP). Subjects were categorized by glycemic status, and the relationship between glycemia and cardiovascular risk factors was investigated using analysis of variance and multiple linear regression analyses. Tertiles of fasting glucose levels showed a clear positive relationship with cardiovascular risk factors including age, obesity, blood pressure, lipid levels, and CRP (P < .001 for all). The overall prevalence of self-reported vascular disease was low, but significantly associated with increasing glycemia. Multiple regression showed that waist circumference (standardized regression coefficient beta = .10, P < .001), triglycerides (beta = 0.16, P < .001), CRP (beta = 0.06, P < .001), female sex (beta = .03, P = .007), high-density lipoprotein cholesterol (beta = -.02, P = .016), and mean arterial pressure (beta = .06, P < .001) were independently associated with fasting glucose levels. Among the normoglycemic subjects (n = 5190), increasing glycemia was still associated with increasing obesity indices, systolic blood pressure, triglyceride, and CRP levels (all P < .05). Increasing glycemia, even in the reference range, is associated with increasing prevalence of vascular risk factors. Control of these risk factors, particularly obesity, the most important avoidable independent determinant of glycemia in normoglycemic subjects, is critical to reduce the risk of the associated vascular disease.

Age Factors↗

PubMed1996

CA 125 kinetics: a cost-effective clinical tool to evaluate clinical trial outcomes in the 1990s.

OBJECTIVE: Our purpose was to determine the importance of the rate of decline of CA 125 relative to conventional prognosticators of ovarian cancer survival to develop a cost effective management algorithm that supports clinical trial research. STUDY DESIGN: By use of a retrospective chart review the slope of the CA 125 exponential regression curve was calculated for 126 women undergoing combination chemotherapy for epithelial ovarian cancer. Univariate and multivariate survival analyses evaluated conventional parameters including age, grade, stage, histologic features, time to initial chemotherapy, dose and treatment intensity, number of cycles to normal CA 125 levels, the intercept from the regression equation, and the slope of the exponential curve. RESULTS: The ideal CA 125 regression rate was calculated at 7.6 days (95% confidence interval 5.9 to 10.7). Univariate analysis determined slope of the CA 125 exponential regression curve (p = 0.0003), number of cycles to normal CA 125 levels (p = 0.0001), residual disease (p = 0.0006), and platinum treatment intensity (p = 0.0001) as the most important predictors of survival. Cox proportional-hazard regression analysis identified slope of the CA 125 exponential regression curve and number of cycles to normal CA 125 levels as the most significant factors for actuarial survival, replacing such conventional parameters as patient age, stage, grade, chemotherapy intensity, and residual disease. None of the factors investigated predicted treatment outcome for patients without residual disease. Multiple linear regression analysis of the slope of the CA 125 exponential regression curve identified intercept of the regression equation, stage, age, and time to initial chemotherapy as important determinants of the slope. CONCLUSION: The slope of the CA 125 exponential regression curve is the single most important prognosticator of actuarial survival for the patient with a CA 125-positive ovarian carcinoma. Treatment algorithms based on this slope may be helpful in developing novel cost-effective clinical trials.

Adult↗

PubMed1999

Secular and seasonal changes in semen quality among young Danish men: a statistical analysis of semen samples from 1927 donor candidates during 1977-1995.

The objective of this study was to investigate whether semen quality has changed during the years 1977-1995 in a group of unselected semen donor candidates, and to determine whether semen quality is subject to seasonal variation, by analysis of time- and season-related changes in semen quality using multiple regression and ANOVA. The study was based on analysis of the first semen sample delivered by 1927 semen donor candidates in Copenhagen during the period 1977-1995, with determination of semen volume, sperm concentration, total sperm count, percentage motile spermatozoa, and a semiquantitative sperm motility score. Multiple linear regression analysis with year, sexual abstinence and season as covariates showed a significant increase in mean sperm concentration from 53.0 x 10(6)/mL in 1977 to 72.7 x 10(6)/mL in 1995 (p < 0.0001) and in mean total sperm count from 166.0 x 10(6) to 227.6 x 10(6) (p < 0.0001). Mean semen volume and percentage motile spermatozoa did not change. Sperm motility deteriorated, as the spermatozoa in 74.2% of the samples were of excellent motility in 1977-1980 compared to only 41.9% in 1993-1995 (chi 2 = 130.0, p < 0.0001). Analysis of variance showed significant variation between seasons regarding sperm concentration (p < 0.0001) and total sperm count (p < 0.0001). Highest sperm counts were found in spring, with a mean concentration (95% C.I.) of 77.6 x 10(6)/mL (71.9-83.7), and lowest in summer, with a mean of 57.5 x 10(6)/mL (50.1-65.4). No other semen parameter varied with season. It is concluded that sperm counts increased, whereas sperm motility decreased, in a group of Danish semen donor candidates, from 1977 to 1995. Due to the retrospective design and the anonymity of the donors, we were unable to control for variation in donor age, and we cannot exclude the possibility that some donor candidates were selected by being accepted as donors by other semen donor services in Copenhagen. With these limitations in mind, we suggest our results should be interpreted cautiously and regarded as a contribution to the ongoing dispute on whether or not there is a continuous decrease in sperm quality. The seasonal variations found in sperm concentration and total sperm count were pronounced and were not attributable to seasonal differences in the length of sexual abstinence. Additionally, the same seasonal pattern was observed in five successive year-intervals. These findings strongly indicate that human testicular function is influenced by season, a phenomenon well known in many lower mammals.

Adult↗

PubMed2003

Epidemiological adaptation of quartz exposure modeling in Swedish aluminum foundries: nested case-control study on lung cancer.

In a recent cohort study in aluminum foundries and remelting plants an unexpectedly high risk of lung cancer was found in workers in sand foundries. On the basis of present and historical measurement data, we developed a statistical model for exposure to total dust and crystalline quartz for different jobs and time periods. Cumulative dose estimates of total dust and crystalline quartz were calculated and used in a nested case-control study in the cohort. From the cohort of foundry workers (n = 5016), 46 cases of lung cancer were identified. The final analysis was performed on 31 cases and 233 controls with one year or more of employment. Historical measurement data from the 1960s and onward were collected, totaling 203 total dust and 103 crystalline quartz exposure observations. Regression models, using the determinants of job title, time period, type of foundry, and size of production, were developed for assessing historical total dust and crystalline quartz air concentrations. These estimates were used to calculate individual cumulative exposure in the case-control study. In the multiple linear regression analysis, the determinants explained much of the variations in dust level (r(2) = 0.58). The explained variation in crystalline quartz was much lower (r(2) = 0.13). The regression coefficients for the type of foundry, time period, and size of production were statistically significant for total dust. On the basis of the regression analysis, the final models were used to calculate individual cumulative exposures. The calculated cumulative dust and quartz exposures averaged 33 mg/m(3) * year and 0.42 mg/m(3) * year, respectively. The odds ratios (ORs) were not significant, but showed dose-response trends for both dust and crystalline quartz.

Aluminum↗

PubMed1988

Combined influence of ventricular loading and relaxation on the transmitral flow velocity profile in dogs measured by Doppler echocardiography.

The relation of the Doppler transmitral flow velocity profile to left ventricular loading conditions and diastolic properties remains poorly described. We studied seven adult mongrel dogs with an open-chest right heart bypass model in which left atrial pressure, representing preload, was varied by controlling blood flow into the pulmonary artery and left ventricular systolic pressure, representing afterload, was controlled independently by pumping blood into or from the femoral arteries. Heart rate was kept constant by crushing the sinus node and pacing the right atrium. Mitral inflow velocity profiles were measured by pulsed-wave Doppler echocardiography at multiple left atrial and left ventricular systolic pressures. In individual dogs, the peak E-wave velocity increased linearly with increasing left atrial V-wave pressure at constant left ventricular systolic pressure and decreased with increasing left ventricular systolic pressure at constant left atrial pressure. Stepwise multiple linear regression analysis of data pooled from all experimental stages in all dogs identified left atrial V-wave pressure, the time constant of relaxation (TL), and left ventricular systolic pressure, in order of decreasing significance, as predictors of the peak E-wave velocity (n = 82, multiple r = 0.87, p less than 0.0001). Multivariate analysis with the same three factors in individual dogs yielded higher r values (mean r = 0.89; range, 0.85-0.97), suggesting the presence of important interdog differences that were not accounted for by these three factors alone. When the values of codeterminant hemodynamic factors were kept within narrower limits, correlations between peak E-wave velocity and left atrial V-wave pressure (n = 35, multiple r = 0.83, p less than 0.0001), TL (n = 76, multiple r = -0.54, p less than 0.0001) and left ventricular systolic pressure (n = 20, multiple r = -0.59, p less than 0.005) improved substantially. In the pooled data, the relation of the peak E-wave velocity to left atrial V-wave pressure was shifted downward by an increase in TL (reduced relaxation rate), and the relation of the peak E-wave velocity to TL was shifted upward by an increase in left atrial V-wave pressure. Multivariate analysis also selected left atrial V-wave pressure and TL as the two most significant correlates of the velocity-time integral and deceleration rate of the E wave.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed2005

Baseline pulmonary function and quality of life 9 years later in a middle-aged Chinese population.

STUDY OBJECTIVE: This research examined the association of baseline pulmonary function with future quality of life (QOL). METHODS: We collected baseline pulmonary function data in 1993 and 1994, and assessed QOL using the Chinese 35-Item Quality of Life Instrument in 2002 in a cohort of 1,356 participants. We used Pearson correlation analysis, multivariate analysis of variance, and multivariate linear regression analysis to assess the relationship between pulmonary function and QOL. RESULTS: The baseline percentage of age- and height-predicted FEV1 (FEV1%) was significantly correlated with the resurvey total QOL score (r = 0.126, p < 0.001) and with QOL scores for the general (r = 0.074, p = 0.006), physical (r = 0.085, p = 0.002), independence (r = 0.178, p < 0.001), and psychological (r = 0.064, p = 0.018) domains but not with the social and environmental domains after adjusting for age and sex. These associations were weaker for the percentage of age- and height-predicted FVC. Multiple linear regression showed that the above associations were independent of baseline and resurvey smoking status. Inclusion of respiratory symptoms in the model reduced the regression coefficients from 0.82 to 0.41 for the total QOL score and from 1.43 to 0.94 for the independence domain score, for a 10% change in FEV1%. The age- and sex-adjusted mean total QOL scores were 78, 76, 76, and 69, respectively (p < 0.001), for the groups of normal, symptomatic only, impaired pulmonary function only, and both symptomatic and impaired pulmonary function. This trend was also significant for the general, physical, independence, and psychological domain scores. CONCLUSION: Impaired baseline pulmonary function has a significant negative impact on QOL in later life that is independent of age, sex, height, and smoking status and is largely mediated through the development of chronic respiratory symptoms.

China↗

PubMed1993

[Determination of height in life using multiple regression of skull parameters].

The Authors have evaluated the possible correlations between cranial diameters and height in a population of 358 young males aged between 17 to 27 years old. The maximum anterior-posterior and lateral cranial diameters were measured along with stature. Then, the data was correlated using the SAS Program (Stepwise method) to obtain a multiple linear regression between height (dependent variable) and the cranial diameters (independent variable). Secondly, the Authors also studied the probable correlation between height and cranial diameters obtained without including the thickness of the soft tissues. In conclusion, they proposed a mathematical formula, applicable in forensic investigation, regarding the determination of the actual living stature of subjects for whom skills are the only skeletal remains available for identification procedures.

Adolescent↗

PubMed2004

Prediction of wheat dough W and P/L inflation test parameters by capillary zone electrophoresis of a protein extract followed by multivariate regression.

A procedure for the evaluation of the wheat flour hardness, based on capillary electrophoresis of a protein extract in an isoelectric acidic buffer, was developed. The 13 flour samples were extracted twice, and two injections of each extract were made. Separations were performed in a background electrolyte (BGE) containing 40 mM aspartic acid, 6 M urea, and 0.5% hydroxyethylcellulose at 60 degrees C. Using the normalized and corrected areas of 79 peaks and peak groups, a partial least squares regression (PLS1) model was able to predict the flour strength or dough deformation work (W) and the dough tenacity/extensibility ratio (P/L) (Alveograph parameters) with an average relative standard deviation in the predictions of +/- 3% and +/-8%, respectively. These values amounted to a +/- 6-8% and +/- 11% with multiple linear regression (MLR) and PLS1 models constructed by measuring only 12 peaks and peak group areas on the electropherograms.

Bread↗

PubMed2001

Analysis of MTR histograms in multiple sclerosis using principal components and multiple discriminant analysis.

Magnetization transfer ratio (MTR) histograms have the potential to characterize subtle diffuse changes in multiple sclerosis (MS) and other white matter disease. A new method is described which gives improved correlation with the Expanded Disability Status Scale (EDSS). Classification of individual subjects into normal and MS subgroups is shown. Principal component analysis (PCA) and multiple discriminant analysis (MDA) are shown to give results superior to methods of MTR histogram analysis using traditional features such as peak height and peak location. Scatterplots confirm the improved separation between groups achieved using the MDA score. The histogram analysis provides a comparison of two classification approaches, based on PCA and MDA, to recognize differences between normal controls and the four different subgroups of MS disease (and all MS patients). Multiple linear regression of these PCs vs. EDSS established an MR-based measure of disease. Using a central 60-mm slab of brain tissue, the success rate of binary classification between control and MS subgroups using MDA was 75-95%, depending on which two groups were being compared. Multiple regression analysis of EDSS with the first three PCs as independent variables was significant (r = 0.83 for secondary progressive MS, and r = 0.80 for all MS patients).

Brain↗

PubMed2005

Determinants of spirometric abnormalities among silicotic patients in Hong Kong.

BACKGROUND: Silicosis is the second commonest notified occupational disease in Hong Kong. AIM: To characterize the determinants of spirometric abnormalities in silicosis. METHOD: The spirometric patterns of consecutive silicotic patients on confirmation by the Pneumoconiosis Medical Board from 1991 to 2002 were correlated with demographic characteristics, occupational history, smoking history, tuberculosis (TB) history and radiographic features by univariate and multiple regression analyses. RESULTS: Of 1576 silicotic patients included, 55.6% showed normal spirometry, 28.5% normal forced vital capacity (FVC>or=80% predicted) but reduced forced expiratory ratio (FER<70%), 7.6% reduced FVC but normal FER, and 8.4% reduced both FVC and FER. Age, ever-smoking, cigarette pack-years, industry, job type, history of TB, size of lung nodules and progressive massive fibrosis (PMF) were all significantly associated with airflow limitation on univariate analysis (all P<0.05), while sex and profusion of nodules were not. Only age, cigarette pack-years, history of TB, size of lung nodules and PMF remained as significant independent predictors of airflow obstruction in multiple logistic regression analysis. After controlling for airflow obstruction, only shorter exposure duration, history of TB and profusion of nodules were significant independent predictors of reduced FVC. As well as age, history of TB, cigarette pack-years, PMF and nodule size contributed comparable effects to airflow obstruction in multiple linear regression analyses, while profusion of nodules was the strongest factor for reduced vital capacity. CONCLUSIONS: In an occupational compensation setting, disease indices and history of tuberculosis are independent predictors of both airflow obstruction and reduced vital capacity for silicotic patients.

Adult↗

PubMed2004

Association between baseline radiographic damage and improvement in physical function after treatment of patients with rheumatoid arthritis.

OBJECTIVES: To identify factors associated with poor physical function in rheumatoid arthritis and to assess whether baseline joint damage has an impact on improvement in physical function during infliximab treatment. METHODS: 428 patients with active rheumatoid arthritis despite methotrexate treatment received methotrexate alone or with infliximab (3 mg/kg or 10 mg/kg every four or eight weeks) for 54 weeks (the ATTRACT trial). Data on clinical outcomes and physical function (assessed by the health assessment questionnaire (HAQ)) were collected. Structural damage was assessed using the van der Heijde modification of the Sharp score. Odds ratios (OR) for factors associated with severe functional disability (HAQ > or =2.0) at baseline were estimated using multiple logistic regression analyses, and baseline factors related to the change in physical function after treatment at week 54 were determined. RESULTS: Baseline radiographic scores were correlated with baseline HAQ scores. After adjustment for demographic characteristics in the logistic regression model, baseline disease activity scores, radiological joint damage, fatigue, and morning stiffness were found to be associated with severe functional disability (HAQ >2.0), with OR values of 2.00 (1.53 to 2.63), 1.82 (1.15 to 2.87), 1.19 (1.05 to 1.34), and 1.07 (1.01 to 1.13), respectively. In multiple linear regression analysis, physical disability, joint damage, and fatigue at baseline were correlated with less improvement in physical function after treatment. Infliximab treatment was associated with greater improvement in physical function. CONCLUSIONS: Greater joint damage at baseline was associated with poorer physical function at baseline and less improvement in physical function after treatment, underlining the importance of early intervention to slow the progression of joint destruction.

Antibodies, Monoclonal↗

PubMed1999

The single-breath transfer factor for carbon monoxide and respiratory symptoms in a Norwegian community sample.

Reduced single-breath transfer factors of the lung for carbon monoxide are seen in a number of conditions. The hypothesis of the present study was that self-reported respiratory symptoms differ in their prediction of TL,CO level in a general population in Norway. A cross-sectional survey of a general population sample in Norway, made up of 1,275 subjects aged 18-73 yrs, was conducted in 1987-1988. The attendees (84% response rate) filled in a questionnaire on respiratory symptoms and underwent standardized spirometric and TL,CO measurements and clinical examination. Associations between TL,CO and respiratory symptoms were assessed using multiple regression models. Tests for interaction were used to examine whether these associations varied with sex, age and smoking habits. Data from 1,221 subjects were analysed. Both males and females who reported respiratory symptoms had significantly lower TL,CO after adjusting for age and height. In a multiple linear regression analysis of TL,CO, adjusting for sex, age, height and smoking habits, the symptoms for which statistical significance was attained, were morning cough, chronic cough and breathlessness. However, only the breathlessness score was independently associated with the TL,CO (-0.42 mmol x min(-1) x kPa(-1) per breathlessness score unit) after adjusting for other respiratory symptoms, and the relationship was stronger in males than in females. In this study, the strongest predictor for a decreased single-breath transfer factor of the lung for carbon monoxide was the presence of self-reported breathlessness, regardless of age, smoking habits and height.

Adolescent↗

PubMed2005

Voice and swallowing outcomes of an organ-preservation trial for advanced laryngeal cancer.

INTRODUCTION: Organ-preservation treatment approaches for advanced laryngeal cancer patients that use combination chemoradiotherapy result in cure rates similar to primary laryngectomy with postoperative radiotherapy. In the national VA Larynx Cancer Trial, successful organ preservation was associated with an overall improvement in quality of life but not in subjective speech compared with long-term laryngectomy survivors. As part of a Phase II clinical trial, a prospective study of speech and swallowing results was conducted to determine if larynx preservation is associated with improved voice and swallowing compared with results in patients who require salvage laryngectomy. SUBJECTS: A total of 97 patients with advanced laryngeal cancer (46 Stage III, 51 Stage IV) were given a single course of induction chemotherapy (cisplatin 100 mg/m2 on Day 1 and 5-FU 1,000 mg/m2/day x 5 days), followed by assessment of response. Patients with less than 50% response underwent early salvage laryngectomy, and patients with 50% or better response underwent concurrent chemoradiation (72 Gy and cisplatin 100 mg/m2 on Days 1, 22, and 43), followed by two cycles of adjuvant chemotherapy (DDP/5-FU). Direct laryngoscopy and biopsy were performed 8 weeks after radiation therapy to determine final tumor response. Late salvage surgery was performed on patients with persistent or recurrent disease. METHODS: Completed survey data on voice and swallowing utilizing the Voice-Related Quality of Life Measure (V-RQOL) and the List Performance Status Scale for Head and Neck Cancer Patients (PSS-HN) were obtained from 56 patients who were alive and free of disease at the time of survey, with a minimum follow-up of 8 months. Comparisons were made between patients with an intact larynx (n = 37) vs. laryngectomy (n = 19), as well as early (n = 12) vs. late salvage laryngectomy (n = 7). Multivariate analysis was performed to determine factors predictive of voice and swallowing outcomes. Overall 3-year determinant survival was 87%, with median follow-up of 40 months. RESULTS: Patients with an intact larynx demonstrated significantly higher (p = 0.02) mean V-RQOL scores (80.3) than did laryngectomy patients (65.4). This finding was consistent in the social-emotional (p = 0.007) and physical functioning domains (p = 0.03). No differences in V-RQOL scores were found in comparisons between early and late salvage laryngectomy. Multiple linear regression revealed that predictors of higher total V-RQOL scores include lower T stage (p = 0.03), organ preservation (p = 0.0007), and longer duration since treatment (p = 0.01). Understandability of speech was better in patients with an intact larynx (p = 0.001). Overall swallowing function was comparable between groups. Multiple logistic regression revealed that longer duration since treatment (p = 0.03, odds ratio = 1.1) and lower maximal mucositis grade (p = 0.03, odds ratio = 0.3) were predictive of higher likelihood of eating in public. Nutritional mode consisting of oral intake alone without nutritional supplements was achieved in 88.9% of patients with an intact larynx compared with 64.3% of laryngectomees (p = 0.09). CONCLUSIONS: Voice-related quality of life is better in patients after chemoradiation therapy compared with salvage laryngectomy. Earlier salvage, although known to be associated with fewer surgical complications, did not result in improved voice; however, the number of patients analyzed is small. Overall swallowing function is good in all patients; however, patients with an intact larynx are more likely to obtain nutrition with oral intake alone without supplements. Such measures of function and quality of life are important endpoints to help judge overall effectiveness as newer, more aggressive treatment protocols with added toxicities are developed and evaluated.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2000

The impact of spinal problems on the health status of patients: have we underestimated the effect?

STUDY DESIGN: A prospective study of 17,774 patients who consulted spine centers in which the impact of spinal disorders and comorbidities on physical functional status were evaluated. OBJECTIVES: To quantify the effect spinal diagnoses have on patients' physical functional status (SF-36 Physical Component Summary [PCS] score) compared with other common conditions and to quantify the effects of comorbidities on physical functional status in spine patients. SUMMARY OF BACKGROUND DATA: The burden of spinal conditions on a patient's function and the role that comorbidities play in this affliction are poorly quantified in the literature. METHODS: Data from the Health Survey Questionnaire were prospectively gathered through the National Spine Network, a nonprofit consortium of spine-focused practices. Each patient's SF-36 score was summarized into a single PCS score. The correlation between diagnosis and comorbidity and PCS score was assessed using multivariate linear regression. RESULTS: The study patients were a mean of 47.5 years of age, 54.7% were female, 52.3% had lumbosacral diagnoses, and 82.0% had had 3 or more months of pain. The population had a mean PCS score of 30.4 +/- 9.95 (SD) compared with 50.0 +/- 10.00 for the general United States population. The more comorbidities in a patient, the lower the PCS score (Spearman rank correlation = -0.27). The five comorbid conditions that lowered the PCS the most included congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), renal failure, rheumatoid arthritis, and lupus (all P <0.001). In multiple linear regression analysis, age, gender, diagnosis, and comorbidity explained 12.1% of the variance in PCS score. CONCLUSIONS: The PCS score is greatly affected in patients with spinal problems. The study population's PCS (30.4) was lower or similar to the PCS for patients with other illnesses reported in the literature: CHF (31.0), COPD (33.9), SLE (37.1), cancer (38.4), primary total hip arthroplasty (29.0), primary total knee arthroplasty (32.6), and glenohumeral degenerative joint disease (35.2). Further, the presence of comorbidity in spine patients adds to the burden of spinal conditions on functional status.

Activities of Daily Living↗

PubMed1997

Linear least squares compartmental-model-independent parameter identification in PET.

A simplified approach involving linear-regression straight-line parameter fitting of dynamic scan data is developed for both specific and nonspecific models. Where compartmental-model topologies apply, the measured activity may be expressed in terms of: its integrals, plasma activity and plasma integrals--all in a linear expression with macroparameters as coefficients. Multiple linear regression, as in spreadsheet software, determines parameters for best data fits. Positron emission tomography (PET)-acquired gray-matter images in a dynamic scan are analyzed: both by this method and by traditional iterative nonlinear least squares. Both patient and simulated data were used. Regression and traditional methods are in expected agreement. Monte-Carlo simulations evaluate parameter standard deviations, due to data noise, and much smaller noise-induced biases. Unique straight-line graphical displays permit visualizing data influences on various macroparameters as changes in slopes. Advantages of regression fitting are: simplicity, speed, ease of implementation in spreadsheet software, avoiding risks of convergence failures or false solutions in iterative least squares, and providing various visualizations of the uptake process by straight line graphical displays. Multiparameter model-independent analyses on lesser understood systems is also made possible.

Algorithms↗

PubMed2004

Does the response of bone mass to calcium supplements depend on calcium absorption efficiency?

OBJECTIVE: Calcium supplements can reduce bone resorption and slow bone loss after the menopause, but these effects may be limited by poor intestinal absorption. Since the increase in blood ionised calcium and decrease in serum parathyroid hormone after a calcium load are diminished in patients with poor calcium absorption, we aimed to see whether the response of bone mineral content (BMC) to calcium is related to initial calcium absorption. DESIGN: We retrospectively examined the changes in forearm BMC in 164 patients (139 women and 25 men) receiving calcium therapy alone for low bone density in a university hospital. METHODS: BMC was measured in a Molsgaard single energy absorptiometer and calcium absorption in a single blood sample 1 h after a dose of 5 microCi (45)Ca in 20 mg calcium carrier. Results were analysed by simple and multiple regression analysis. RESULTS: Mean forearm BMC did not change significantly over the mean 43 (S.D., 33) months of treatment (1.023 (0.247) to 1.017 (0.246) g/cm). The annual percentage of change was positively related to both body weight (r=0.180; P=0.020) and radiocalcium absorption (r=0.185; P=0.017). Multiple linear regression confirmed that both variables contributed to the change in BMC (P=0.023 and 0.019 respectively). The mean annual percentage of change in BMC on calcium therapy was not related to age, initial BMC, serum 1,25-dihydroxyvitamin D or fasting urinary calcium/creatinine ratio. CONCLUSIONS: These results support our earlier studies which suggest that poor calcium absorption limits the response of bone to calcium supplements.

Adult↗

PubMed1999

Factors affecting left ventricular mass regression after aortic valve replacement with stentless valves.

The hemodynamic benefits of using stentless valves for replacement of the human aortic valve have become more well known. These devices are associated with significant decrease in left ventricular (LV) mass and LV remodeling in the early postoperative period. However, no large study has examined patient-related and valve-related factors that may contribute to this phenomenon. This study examined 1,103 patients who underwent aortic valve replacement (AVR) with a stentless porcine valve (Freestyle = 840, SPV = 263). In all cases, a subcoronary implant technique was used. Valve performance was assessed by serial echocardiograms. At 3 years' post-AVR, mean gradient was 6.3+/-5.0 mm Hg, and effective orifice area (EOA) was 2.0+/-0.7 cm2. Indexed EOA was 1.2+/-0.4 cm2/m2. There was an association between indexed EOA and the extent of LV mass regression. At 3 years after surgery, LV mass index (LVMI) was reduced to 76.3% to 78.7% of baseline in patients whose indexed EOA was >0.8 cm2/m2. In contrast, for patients with an indexed EOA that was <0.8 cm2/m2, LVMI at 3 years was 95.5% of baseline (P = .0001). Multiple linear regression models were used to identify parameters that predicted the 3-year LVMI. Baseline LVMI (P<.0001), prior myocardial infarction (P = .0009), male gender (P = .0036), and carotid stenosis (P = .022) were independent predictors of LV mass regression. Valve type, valve size, preoperative New York Heart Association class symptoms, coronary disease, prior bypass surgery, chronic obstructive pulmonary disease, or underlying valve pathology had no effect on LV mass regression. Data indicate that baseline LVMI and patient-prosthetic mismatch have major effects on the extent of LV mass regression post-AVR. Long-term hemodynamic benefits of AVR can be optimized by proper selection of the prosthesis so as to avoid mismatch. Furthermore, because the baseline LVMI affects the extent of regression post-AVR, early intervention may result in more complete resolution of LV mass postoperatively, which may have important prognostic implications.

Aged↗

PubMed2003

Identifying confounds to increase specificity during a "no task condition". Evidence for hippocampal connectivity using fMRI.

Functional MRI can be applied to study connectivity in the brain during a "no task condition." This study focuses on applying a multiple linear regression analysis to identify spurious connectivity caused by confounding factors such as physiologic noise and to separate these from hippocampal connectivity caused by the blood oxygen level dependent (BOLD) signal during a no-task condition. Regressors of interest (hippocampal time courses) as well as regressors of no interest (respiratory signal and cerebrospinal fluid), were included in the analysis, and each yielded a connectivity map. This method was applied at high sampling rate (limited volume, proper physiologic noise sampling), low sampling rate (whole brain scans possible), and at high and low spatial resolution in five healthy control subjects. Regressors of no interest showed specific connectivity patterns, different from hippocampal regressors. The latter showed connectivity between left and right hippocampus. The current study shows successful application of a multiple regression analysis to study connectivity between left and right hippocampus. Both maps of hippocampal connectivity caused by BOLD signal and connectivity caused by spurious signals could be identified.

Adult↗