Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Statistical Regression”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 1,369 records · Page 76Linked to original sources
PubMed2007

Tibolone therapy in breast cancer survivors: a retrospective study.

AIM: To investigate a possible relationship between tibolone therapy and recurrence or mortality in breast cancer survivors. METHODS: In a retrospective study, data from files of 247 patients who had been treated for breast cancer were analyzed. Twenty women were treated with tibolone because of menopausal symptoms (Group 1: mean duration of tibolone use 37.1 months). One hundred and one women who did not take tibolone were selected as the control group (Group 2). All women were followed up in our Department on our standard protocol (mean follow up: 73.4 months in Group 1, 67.4 months in Group 2). Comparison of the survival curves was applied with the Wilcoxon (Gehan) statistic. Cox regression analysis was also applied in order to identify significant coefficients in the survival curve. RESULTS: Recurrence of breast cancer was observed in two (10%) Group 1 women versus 21 (21%) Group 2 women (P = NS). Two Group 1 women died (one from breast cancer recurrence) versus 15 Group 2 women (14 from breast cancer recurrence). CONCLUSIONS: Despite of the inherent limitations of this small retrospective study, it seems that tibolone does not reveal an apparent negative impact on breast cancer outcome when given to breast cancer survivors.

Adult↗
PubMed1994

Urothelial cancer and cigarette smoking: findings from a regional case-controlled study.

OBJECTIVE: To quantify the risks of urothelial cancer associated with smoking cigarettes. SUBJECTS AND METHODS: Histories were taken from 989 patients diagnosed with urothelial cancer, 2059 electoral register controls and 1599 General Practitioner controls. Histories of patients and controls were compared by means of logistic regression. RESULTS: Statistically significant trends were observed for the risk of urothelial cancer to increase with estimated lifetime consumption of cigarettes. Among ex-smokers, risks reduced with time since quitting, and ex-smokers who quit 20 or more years ago experienced risks similar to lifelong non-smokers. Type of cigarette was not an important predictor of risk. The two control series provided estimates of 45% and 33% respectively for the percentage of cancers in the series attributable to cigarette smoking. CONCLUSION: Cigarette smoking is the single most important cause of urothelial cancer, but stopping smoking leads quickly to reductions in risk.

Adolescent↗
PubMed1975

Rate of fall in plasma progesterone and time to abortion following intra-amniotic injection of prostaglandin F2alpha, with or without urea, in the second trimester of human pregnancy.

Progesterone concentrations have been determined in a total of 175 peripheral plasma samples obtained serially from 20 women undergoing mid-trimester abortion. In ten patients abortion was induced in intra-amniotic administration of 50 mg. of prostaglandin F2alpha (PGF 2alpha) alone; in ten others it was induced with 50 mg. of intra-amniotic PGF2alpha with 80 g. of urea. Mean instillation-abortion intervals were 29-0 hours in the group receiving PGF2alpha alone and 12-1 hours in the groups receiving PGF2alpha and urea. In eight of the patients treated with PGF2alpha and urea, and in four of those treated with PGF2alpha alone, there were significant decreases in progesterone level (determined by calculation of correlation coefficients) during the instillation-abortion iterval. When plotted against instillation-abortion times, calculated rates of decease in peripheral plasma progesterone levels showed a statistically significant regression (p smaller than 0-05). This indicates that progesterone levels drop most rapidly in patients with shorter instillation-abortion times. There was no relationship between initial progesterone levels and instillation-abortion times.

Abortion, Induced↗
PubMed1991

The effect of induced abortion on subsequent pregnancy outcome.

OBJECTIVE: To investigate the effect of induced abortion on the outcome of the next pregnancy. DESIGN: Long-term prospective controlled cohort study. SETTING: Joint Royal College of General Practitioners/Royal College of Obstetricians and Gynaecologists study based in general practice in England, Scotland and Wales. SUBJECTS: 1311 women whose recruitment pregnancy had ended in induced abortion (the abortion group) and 2131 women whose recruitment pregnancy had a natural conclusion (the non-abortion group). MAIN OUTCOME MEASURES: Non-viable outcome (spontaneous or missed miscarriage, ectopic pregnancy or stillbirth), birthweight, length of gestation. RESULTS: Induced abortion was not materially associated with any of the three measures of adverse outcome. Compared with the non-abortion group the relative risk of a non-viable outcome in the abortion group was 1.01 (95% CI 0.81 to 1.27). In the abortion group birthweight was an average 23 g lighter (95% CI -76 g to + 30 g) and length of gestation an average 0.9 days shorter (95% CI -2.2 days to + 0.4 days) than in the non-abortion group. Women who had their abortions in NHS premises had an increased risk of a non-viable outcome (RR 2.55, 95% CI 1.31 to 4.94) and had babies with significantly lower mean birthweight (-119 g, 95% CI -233 g to +5 g) compared with those who obtained their operations in the private sector. Women whose abortion had been carried out by a consultant had the lowest risk of non-viable outcome. Although these differences remained after adjustment for a number of important variables, it is possible that factors not measured in the present study, such as economic status and occupation, played a contributory role. CONCLUSION: Overall, induced abortion was not associated with any important effect on the three measures of adverse outcome in the subsequent pregnancy.

Abortion, Induced↗
PubMed2004

The effects of state mental health parity legislation on perceived quality of insurance coverage, perceived access to care, and use of mental health specialty care.

OBJECTIVE: To assess the impacts of recent state mental health parity legislation on perceived quality of health insurance coverage, perceived access to needed health care, and use of mental health specialty services by individuals with likely need for mental health care. DATA SOURCES: The study sample came from two waves of a national household survey first fielded in 1997-1998 and then in 2000-2001. The analysis used a subset of the sample. STUDY DESIGN: The study took the Difference-in-Difference-in-Difference approach to investigate changes in self-perceived quality of health insurance coverage and access to needed health care, and use of mental health specialty care by the group with mental disorders (relative to those without) in states with parity legislation of different comprehensiveness (relative to the nonparity states) in the years after the law (relative to before the law). PRINCIPAL FINDINGS: Overall, there were no significant or consistent effects of the parity legislation. Descriptive statistics showed significant changes in some (but not all) outcome variables, but these results disappeared in detailed statistical analyses by controlling for important covariates. CONCLUSIONS: The null findings of the effects of state mental health parity mandates suggest that under ERISA (Employee Retirement Income Security Act), the scope of state parity legislation may have been restricted because of large proportion of self-insured employers. Furthermore, comprehensiveness of state legislation appears to be related to the traditional level of use of mental health specialty care, which becomes another confounder for the potential policy effects.

Attitude to Health↗
PubMed2005

Modeling the implications of changes in vascular calcification in patients on hemodialysis.

BACKGROUND: The Treat-to-Goal Study found that sevelamer slowed the progression of coronary calcification in patients on hemodialysis compared to calcium-based phosphate binders. To understand the implications of this effect for cardiovascular events, risk equations are needed. METHODS: Data on 179 patients on hemodialysis treated at one center in France included biochemical values during the year prior to study entry, patient characteristics, and cardiovascular events over an average of 4 years. As arterial calcification was evaluated ultrasonographically and quantified using a 0 to 4 score, an equation relating this to the electron-beam tomography (EBT)-based calcification score used in the trial was developed and applied to all patients. The estimated scores were then used in survival and Cox proportional hazards analyses of cardiovascular events in relation to the degree of calcification, controlling for other characteristics. RESULTS: Mean age at inclusion was 54 years, dialysis vintage 70 months, average follow-up 49 months; 32% suffered an event. The calcification score, diabetes, C-reactive protein (CRP), diastolic blood pressure, gender, smoking and hypertension are independent predictors of cardiovascular risk. The resulting equation indicates that, relative to a calcification score below 400, the risk of an initial event increases 44% for a score of 600, and more than doubles for a score of 1000. CONCLUSION: In the absence of long-term follow-up studies, these equations permit quantification of the expected long-term clinical consequences of the impact of various phosphate binders on vascular calcification. Together with resource use and cost information, these equations are key inputs for formal cost-effectiveness analyses.

Blood Pressure↗
PubMedDate not supplied

Quantum pharmacologic studies applicable to the design of anticonvulsants: theoretical conformational analysis and structure-activity studies of barbiturates.

We report the first large-scale systematic quantitative structure-activity relationship (QSAR) study of barbiturates, correlating molecular structures with anticonvulsant activity. To achieve this QSAR study, we devised a four-step strategy. In step 1, an optimal quantum mechanical technique for determining the geometry and shape (conformation) of barbiturates was ascertained; this is the AM1 semiempirical molecular orbital method. In step 2, the AM1 method was used to optimize the structures and molecular properties of 48 barbiturates with varying anticonvulsant activity. In step 3, discriminant analysis and regression analysis statistical calculations were used to correlate the molecular properties of the 48 analogues against maximal electroshock (MES) and subcutaneous metrazol (s.c.Met)-induced seizures. In step 4, the contribution of molecular electrostatic properties to barbiturate anticonvulsant activity was further refined by quantum mechanical derived molecular electrostatic potential (MEP) maps. Using this four-step strategy, we defined the pharmacophore, the portion of a molecule responsible for bioactivity, for anti-MES and anti-s.c.Met activity. For anti-s.c.Met activity, barbiturate lipophilicity and geometry are important considerations; for anti-MES activity, barbiturate topologic and electronic properties have increased relevance.

Anticonvulsants↗
PubMed1993

Dimensions of risk perception for financial and health risks.

This study of 29 MBA students compares two models of risk perception for both financial and health risk stimuli. The first, inspired by Luce and Weber's Conjoint Expected Risk (CER) model, uses five dimensions: probability of gain, loss and status quo, and expected benefit and harm. The second, inspired by the Slovic et al. psychometric model, employs seven dimensions: voluntariness, dread, control, knowledge, catastrophic potential, novelty, and equity. The CER-type model provided a better fit for most subjects and stimuli. Adding the psychological risk dimensions from the Slovic et al. model explained only modestly more variance. Relationships between the dimensions of the two models are described and the construction of a hybrid model explored.

Accidents↗
PubMed1998

Effect of 50 milliliters of 50% dextrose in water administration on the blood sugar of euglycemic volunteers.

OBJECTIVE: To evaluate the effect of administration of 1 ampule of 50% dextrose in water solution (D50W) on serum glucose levels in healthy adult volunteers, the authors set out to determine whether a pre-D50W serum glucose level can be predicted from the ED sample. METHODS: This was a prospective, interventional study conducted from the ED of an urban, university-affiliated hospital. All subjects were healthy employee volunteers between 25 and 40 years of age. Baseline serum glucose levels were determined and all subjects were given an i.v. bolus of 25 grams of 50% dextrose solution. The main outcome measures were post-D50W serum glucose levels (observed) at 5 predetermined time intervals (5 min, 15 min, 30 min, 1 hr, and 2 hr). An expected change in serum glucose was calculated using the volume of distribution formula for glucose. RESULTS: Twenty-five volunteers (17 males and 8 females) participated in the study. The mean baseline serum glucose was 82.3 +/- 13.5 mg/dL. The mean post-infusion levels were: 244.4 +/- 44.6 mg/dL (5 min), 145.8 +/- 52.3 mg/dL (15 min), 88.1 +/- 28.8 mg/dL (30 min), 77.6 +/- 13.6 mg/dL (60 min), and 83.2 +/- 11.4 mg/dL (120 min). Using a mixed-effect regression model, statistically significant increases in serum glucose levels were found at 5 minutes (p < 0.001) and 15 minutes (p < 00001) following administration of D50W. There was a return to baseline serum glucose by 30 minutes. The expected change based on the volume of distribution formula (53.7 +/- 34.9) did not correlate with the observed changes at any measured time interval. CONCLUSION: Without pre-intervention blood drawing by emergency medical services, it is not possible to accurately predict pre-D50W serum glucose levels based on post-D50W glucose levels. The diagnosis of hypoglycemia as the etiology of altered mental status must therefore remain a diagnosis of exclusion. In addition, the return of serum glucose to baseline after 30 minutes suggests the duration of the effect of 1 ampule of D50W. Frequent re-evaluation of the serum glucose levels of suspected or proven hypoglycemic patients after administration of D50W should be considered.

Adult↗
PubMed2003

The effect of a new emergency medicine residency program on patient length of stay in a community hospital emergency department.

OBJECTIVES: It is not clear how emergency medicine residents affect emergency department (ED) efficiency. The objective of this study was to determine whether a new emergency medicine residency program affected the length of stay (LOS) of patients in a community hospital ED. METHODS: A before-and-after observational study was conducted during a one-year period prior to, and for three years after, the start of a new residency. An additional year's worth of data were collected during the fifth year after the residency started. Patients were excluded if their LOS was less than 30 minutes and they were admitted directly to the hospital. Explanatory variables included scheduled resident and student hours/day; scheduled faculty hours/day; nursing plus clerk hours/day; patients/day; ambulances/day; and admissions/day. The data were analyzed using descriptive and correlation statistics and regression analysis. RESULTS: Average patient LOS prior to the residency was 122.9 minutes. During the first year of residency, it was 126.6 minutes; second year, 129.9 minutes; third year, 158.9 minutes; and fifth year, 162.4 minutes. There was a positive correlation between LOS and third-postgraduate-year resident (PGY-3) hours (rho = 0.43), and between LOS and PGY-3 hours/patients/day (rho = 0.42). All other correlations were poor (rho < 0.4). CONCLUSIONS: In this ED, there was a weak, positive correlation between ED patient length of stay and the presence of PGY-3 emergency medicine residents.

Analysis of Variance↗
PubMed2001

Risk factors for erosive reflux esophagitis: a case-control study.

OBJECTIVES: It is presently not fully understood which risk factors contribute to the occurrence of reflux esophagitis and how such factors might influence the severity of the disease. The aim of this study was to delineate the clinical epidemiology of erosive reflux esophagitis. METHODS: Outpatients from a medicine and gastroenterology clinic who underwent upper GI endoscopy were recruited into a case-control study. A total of 1,533 patients with and 3,428 patients without endoscopically diagnosed reflux esophagitis were categorized as case and control subjects, respectively. Using multivariate logistic regressions for statistical analysis, the presence of esophageal erosions, ulcers or strictures, served as three separate outcome variables. Demographic characteristics, intake of nonsteroidal anti-inflammatory drugs (NSAIDs), consumption of alcohol and cigarettes, and the presence of hiatus hernia or peptic ulcer served as predictor variables. RESULTS: Erosive reflux esophagitis tended to occur more frequently in Caucasian male patients. Hiatus hernia was associated with a strong risk for developing esophageal erosions, ulcers, and strictures. Although statistical significance was demonstrated only for esophageal erosions, in all grades of reflux esophagitis alike, gastric and duodenal ulcer exerted a protective influence. Consumption of NSAIDs increased the risk for esophageal ulcers only. Smoking and alcohol were not associated with an increased risk of developing any type of erosive reflux esophagitis. CONCLUSIONS: The results stress the critical role played by hiatus hernia in all grades of erosive reflux esophagitis. NSAIDs may act through a mechanism of topically induced esophageal injury. Our data also suggest that the presence of either gastric or duodenal ulcer exerts a protective influence against the development of reflux disease.

Adult↗
PubMed1978

Biological variation of immunoglobulin concentrations in normal human tears related to age and sex.

Single radial immunodiffusion method was used to measure the concentration of IgG, IgA, IgM and IgD in tears of 220 healthy individuals aged from 2 to 86 years. Relation of the values to age and sex has been evaluated statistically by regression analysis method. Mean IgA level was 30.7 mg/100 ml. IgG could be detected in 200 samples and the level was less than 1 mg/100 ml. IgM was detected in only 7 samples and the value was less than 1 mg/100 ml. IgD could not be detected in any of the sample. The IgA level in males and that in females differs significantly, the females having a higher mean value. The IgA level appears to increase in both sexes with age. No relationship with age and sex could be established in other types of immunoglobulins.

Adolescent↗
PubMed1968

The response to stretch of muscle spindle afferents of baboon's tibialis anticus and the effect of fusimotor stimulation.

1. Systematic studies of the response of baboon's tibialis anticus muscle spindles to stretch were undertaken. Most of the spindle afferents studied had conduction velocities between 72 and 78 m/sec with a range from 39 to 93 m/sec. There was no clear bimodality in the histogram of the conduction velocity. Measurements were made of the axon diameters of the nerve to tibialis anticus. The largest number of the larger axons had diameters from 11 to 13 mu. The largest axon diameter measured 17 mu and there were very few of these.2. The dynamic index for any given afferent tended to be greater for the more rapidly conducting afferents and lower for the more slowly conducting afferents. However, a statistically significant regression line of this relationship could only be drawn for a stretch velocity of 64 mm/sec.3. The spindle afferent response to stretch was studied from different muscle lengths. It was found that the velocity sensitive portion of the response to phasic stretch decreased when the stretch extended up to or beyond the maximum physiological length of the muscle.4. Dynamic and static fusimotor fibres were isolated. The response of the spindle afferent to stretch, while the dynamic fusimotor fibre was being stimulated, was the same as that reported for the cat by P. B. C. Matthews (1962). During static fusimotor stimulation the response of the spindle afferent to stretch was usually like that reported for the cat. In a single case, however, static fusimotor stimulation resulted in a lowering of the peak frequency of the response of the spindle afferent to the phasic portion of stretch.

Action Potentials↗
PubMed2003

Effect of specimen size and aspect ratio on the tensile properties of porcine aortic valve tissues.

The measurement of mechanical properties of biological tissues is subject to artifacts such as natural variability and inconsistency in specimen preparation. As a result, data cannot be easily compared across laboratories. To test the effects of variable specimen dimensions, we systematically modified the size and aspect ratio (AR) of porcine aortic valve tissues and measured their stiffness and extensibility. We found that: (i) as the AR of circumferential specimens increased from 1:1 to 5:1, their stiffness increased by 36% (p < 0.001) and their extensibility decreased by 21% (p < 0.001); (ii) as the AR of radial specimens increased from 0.8:1 to 4:1, their stiffness increased by 36% (p < 0.001) and their extensibility decreased by 34% (p < 0.001); (iii) as the size of circumferential specimens was reduced from 128 to 32 mm2 at fixed AR (2:1), their stiffness decreased by 6 (p = 0.05), and their extensibility increased by 17% (p < 0.001); and (iv) as the size of radial specimens was reduced from 72 to 32 mm2 at fixed AR (2:1), their stiffness decreased by 7% (p = 0.03) and their extensibility increased by 16% (p = 0.005). Thus, as specimens of constant length became narrower, they became stiffer and less extensible, and as specimens of fixed aspect ratio became smaller, they became less stiff and more extensible. Statistical models of these trends were predictive and can thus be used to integrate materials test data across different laboratories.

Animals↗
PubMed2004

Spatiotemporal encoding of a bar's direction of motion by neural ensembles in cat primary visual cortex.

Directionally selective neurons strongly fire when presented with a preferred direction of motion of a bar and only weakly respond otherwise. Intuition suggests these "specialist" neurons would be better suited to report this stimulus feature to higher visual centers than "generalist" neurons, neurons that broadly modulate their activity to the feature. However, as stimuli are encoded not by one cell but by large neural ensembles, we have studied the role of single-cell receptive field properties in stimulus representation. Using regression error statistics, we compared the performance of direction-of-motion estimators, using ensembles of neurons selectively responding to direction of motion and estimators using ensembles not specializing to direction. We found that direction-selective ensembles were no better at representing a bar's direction of motion than nonselective ensembles. Quite the opposite, the nonselective unit ensembles provided a better estimate of the direction (standard deviation of the error of 33 degrees) than the direction-selective ensembles (standard deviation of the error of 42 degrees). The nonselective neurons provided information through a latency code that is apparent only when a neuron's activity is considered in the context of the responses of neighboring neurons. These results suggest that models utilizing both generalist and specialist neurons may better reflect the encoding mechanisms that take place in sensory pathways.

Action Potentials↗
PubMed1998

A general approach for multidimensional smoothing.

Smoothing is closely related to regression in statistics. It is frequently applied to data that contain statistical noise in attempts to discern and highlight patterns concealed in the data. In medical imaging applications, the acquired data are often N dimensional (where N > or = 2) and thus multidimensional smoothing approaches would best exploit the multidimensional correlations inherent in the data. Unfortunately, extensions of advanced (especially adaptive) one-dimensional smoothing approaches to multidimensional data are, in general, theoretically challenging and computationally prohibitive. In this work, we propose a novel approach that accomplishes effectively higher-dimensional smoothing by exploiting the Fourier transform properties of the data to reduce data dimensions, allowing for lower-dimensional smoothing. We present the theoretical basis for this approach and verify this approach by applying it to computer-simulated data as well as real data acquired in medical imaging studies.

Bone and Bones↗
PubMed2006

The effects of strength training on memory in older adults.

The authors examined whether resistance training has an effect on working memory span. Participants included 210 community-residing older adults with at least one disability from the Strong for Life program, a randomized controlled trial that examined the effects of home-based resistance exercise. Memory was assessed with the WAIS backward digit span at baseline and 3 and 6 months into the intervention. Although there were no differences between the experimental treatment and control groups in average levels of memory change, within the treatment group change in resistance level during the intervention was a significant predictor of memory change, controlling for age, education, sex, and disability level. The results suggest that strength training can benefit memory among older adults, especially when using higher resistance levels.

Aged↗