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PubMed1990

A note on the use of statistical models in epidemiologic research on illicit drug use.

This essay aims to stimulate thinking or to remind readers about the shortcomings of standardized regression coefficients and related statistical measures in epidemiologic research on illicit drug use. This is accomplished primarily with a set of examples based on simulated epidemiologic data in which the standardized regression coefficient is shown to co-vary dramatically with frequency of the outcome variable. The basic thrust of this critique of commonly used regression models is not new; it has appeared elsewhere several times. Nevertheless, in epidemiologic research on illicit drug use, there is a continuing use of standardized regression coefficients and other margin-sensitive statistical measures without comment on their shortcomings. Thus, a specific critique with illustrations might have value.

Adolescent↗
PubMed1983

Sister chromatid exchange in the centromere and centromeric area.

Central and peripheral sister chromatid exchanges (SCE) were evaluated separately in human phytohemagglutinin (PHA)-stimulated lymphocytes after culture for 72 h in 5-bromodeoxyuridine (BrdU) containing medium. At the same time, the length of chromosome No. 1 was measured in 10 metaphases per case and the mean value taken as a representative parameter for the contraction of chromosomes. The statistical analysis of regression revealed a close relationship between the percentage of SCE observed in the centromere and the contraction state of chromosomes (P less than or equal to 0.01). A statistically significant increase of central exchanges was seen in more condensed chromosomes, due to the difficulty in differentiating clearly between centric and pericentric exchanges. Consequently, if exchanges in the centromere are omitted from evaluation, this would lead to spuriously low SCE rates in more contracted chromosomes. In order to exclude the variable factor of chromosome contraction in SCE studies, we highly recommend inclusion of counts of central exchanges. Results obtained on chromosomes with twisted chromatids, a situation which tends to stimulate SCE, should be omitted.

Centromere↗
PubMed2025

Medical genetics and genomics residency programs: Trends in applications, match rates, and matriculation from 2015 to 2024.

PURPOSE: This report analyzes Medical Genetics and Genomics (MGG) training trends from 2015 to 2024. Understanding such trends is vital for developing targeted recruitment and workforce development initiatives. METHODS: Matriculation data from the American Board of Medical Genetics and Genomics (ABMGG) and publicly available data from the National Resident Matching Program (NRMP) Main Residency and Specialty Matches were reviewed. Descriptive statistics and linear regression analysis were used to compare growth among MGG training pathways and to analyze trends. RESULTS: From 2015 to 2024, there has been a small, but not statistically significant, increase in the total number of individuals who have matched into categorical MGG, combined Pediatrics (Peds)-MGG, and combined Internal Medicine (IM)-MGG residency programs as a whole. This has been driven by an increase in the number of matches to combined Peds-MGG programs. Matriculation into training programs has exceeded the number of matches in categorical MGG as some positions have been filled outside of the NRMP Match. The average match rate for all applicants in categorical MGG (87%) has been higher than that for Peds-MGG (52%). CONCLUSION: Growth in applicants to combined programs and matriculation into residency programs after the NRMP Match has been promising; however, these increases are not enough to fulfill growing workforce demands.

Internship and Residency↗
PubMed2000

Prevalence and psychosocial impact of urinary incontinence in older people of a Spanish rural population.

BACKGROUND: The prevalence and the psychosocial impact of urinary incontinence in older people of a rural population were investigated. METHODS: A cross-sectional study was made by means of a home health interview in a representative sample of people aged 65 years and older in the Basic Health Zone of Cabra (Córdoba). A questionnaire was used with two questions to detect urinary incontinence and further questions regarding its duration, frequency, volume, severity and psychosocial impact. Data were analyzed with basic statistics. A logistic regression model was created to identify which factors affect people's lifestyles. RESULTS: Among the 827 respondents the prevalence of incontinence reached 36% [95% confidence interval (CI): 34%-38%] and was higher (p < .001) in women (42%; 95% CI: 39%-45%) than in men (29%; 95% CI: 25%-38%). The most frequent duration of incontinence was from 1 to 5 years (16.8%). Fifteen percent had daily episodes and 10.6% estimated the volume of urine loss as high. Incontinence was severe in 9% of the affected subjects. Half the incontinent subjects expressed social limitations and negative feelings related to incontinence, and 21% admitted that incontinence negatively affected their lives. In the logistic regression model, both volume of urine loss [odds ratio (OR) = 5.61; 95% CI: 2.76-11.42] and being married (OR = 2.34; 95% CI: 1.03-5.33) were the factors statistically associated with a negative influence of incontinence on lifestyle. CONCLUSIONS: Urinary incontinence is a very frequent symptom in our population. Half the incontinent subjects suffer from some degree of psychosocial limitation. The volume of urine loss and being married are the most important factors with psychosocial impact.

Activities of Daily Living↗
PubMed2004

Identifying estrogen receptor alpha target genes using integrated computational genomics and chromatin immunoprecipitation microarray.

The estrogen receptor alpha (ERalpha) regulates gene expression by either direct binding to estrogen response elements or indirect tethering to other transcription factors on promoter targets. To identify these promoter sequences, we conducted a genome-wide screening with a novel microarray technique called ChIP-on-chip. A set of 70 candidate ERalpha loci were identified and the corresponding promoter sequences were analyzed by statistical pattern recognition and comparative genomics approaches. We found mouse counterparts for 63 of these loci and classified 42 (67%) as direct ERalpha targets using classification and regression tree (CART) statistical model, which involves position weight matrix and human-mouse sequence similarity scores as model parameters. The remaining genes were considered to be indirect targets. To validate this computational prediction, we conducted an additional ChIP-on-chip assay that identified acetylated chromatin components in active ERalpha promoters. Of the 27 loci upregulated in an ERalpha-positive breast cancer cell line, 20 having mouse counterparts were correctly predicted by CART. This integrated approach, therefore, sets a paradigm in which the iterative process of model refinement and experimental verification will continue until an accurate prediction of promoter target sequences is derived.

Animals↗
PubMed1995

Statistical modelling in analysis of outcome after trauma Glasgow-Coma-Scale and Innsbruck-Coma-Scale.

AIM OF THE STUDY: The current study investigated the Glasgow-Coma-Scale (GCS) and the Innsbruck-Coma-Scale (ICS) for accuracy and reliability of prehospital prediction of non-survival. METHODS: 254 patients were scored immediately after trauma. RESULTS: Both scales equally predicted non-survival with low scores (p < 0.001). The ICS was slightly better in overall prediction of patient outcome (ICS: 84.98%; GCS: 82.68%), but more importantly, statistical analysis (logistic regression model) showed a greater distance between the median scores of survivors and non-survivors, when scored with the ICS (survival: 12; non-survival: 3) than when scored with the GCS (survival: 7; non-survival: 4). CONCLUSION: The results of the present study not only suggest that it is possible to predict mortality prior to therapy for any individual GCS and ICS coma score, but also indicated the ICS to be safer to use than the GCS because of the greater distance of the median scores for survivors and non survivors.

Adolescent↗
PubMed1998

Statistical analysis of data pertaining to complex state systems by stepwise regression with reformulated parameters; application to spectroscopically monitored hemoglobin oxygen binding data.

A method is described for the statistical analysis of data pertaining to complex state systems, based on the concept of reformulating the parameters describing the system as a hierarchy of interactions, and this method demonstrated on the analysis of spectroscopically monitored hemoglobin oxygen binding data [K. Imai, Biophys. Chem. 37 (1990) 197-210]. The concept of reformulation was first extended to state parameters other than delta G degree s, such as the extinction coefficients (epsilon s) associated with different ligation states during hemoglobin oxygen binding. The reformulated parameters are incrementally allowed to vary in the data fitting procedure, and the statistical significance of the added parameters tested by F and Kolmogorov-Smirnov tests. The result of this method is the minimal set of statistically significant parameters required to describe the data. The hierarchical nature of reformulated parameters allows the physical significance of the subset of statistically significant parameters to be discussed even when all reformulated terms may not be statistically significant. Applying this method to hemoglobin oxygen binding data with the reformulated Adair model demonstrated that at least two, and at most three, of the four reformulated Adair constants are statistically significant. A reformulated square model was found to give a statistically indistinguishable fit from the Adair model, with the statistically significant thermodynamic terms essentially those proposed by Linus Pauling in 1935. A change in delta epsilon with subsequent oxygen binding events was found to be significant in both models. These results are consistent with a model for hemoglobin oxygen binding where a subunit changes its conformation upon oxygen binding, and affects the conformation of adjacent subunits.

Data Interpretation, Statistical↗
PubMed2005

The effect of time to peak ankle torque on balance stability boundary: experimental validation of a biomechanical model.

Pai and Patton (1997), using a biomechanical model, determined a set of feasible center of mass (CM) velocity-position combinations (balance stability boundary) that guarantee upright stability. In their study, the magnitude of the restoring ankle torque was used to study the subject's ability to recover balance. Recent studies have suggested that the ability to maintain a stable posture depends not only on the magnitude of the restoring torque but also on the time to generate this torque. The objectives of the present study were: (1) to build a biomechanical model that predicts the balance stability boundary which includes time to peak ankle torque, (2) to determine the capability of the model to predict successful and failed experimental balance recovery trials, and (3) to compare the predictive capability of the biomechanical model with that of a statistical model (logistic regression). A single-link-plus-foot biomechanical model was used to determine a set of balance stability boundaries, computed from the combination of maximum CM velocity and related CM position, for various times to peak ankle torque. An experiment was conducted to validate the biomechanical model. The participants self-initiated a forward destabilization and were asked to regain balance using an ankle feet-in-place strategy. Also, a forward stepwise logistic regression (predictors: CM position and velocity and time to peak ankle torque) was used to discriminate between successful and failed experimental trials. (1) The outcomes of the biomechanical model confirmed that the time to peak ankle torque drastically constrained the stability boundaries. (2) The biomechanical model predicted 79.9% of the failed experimental trials and 74.5% of the successful experimental trials. (3) The stepwise logistic regression included all independent variables and predicted 57.2% of the failed and 93.7% of the successful experimental trials. Hence, the biomechanical model showed better predictive capability than the statistical model for identifying unsuccessful balance recovery. It is noteworthy that the balance stability boundaries constrained by the speed of ankle torque development predicted the outcome of the experimental trial earlier in the time series than balance stability boundary constrained by constant ankle torque. Overall, the present biomechanical model may serve as an assessment tool to develop specific interventions towards improving a patient's speed of ankle torque development and to possibly reduce falling frequency.

Accidental Falls↗
PubMed2003

Methodological and statistical techniques: what do residents really need to know about statistics?

The purpose of this study was to catalog the statistical methods used in six journals two each from the fields of Family Practice, Emergency Medicine, and Obstetrics and Gynecology. We reviewed the quantitative articles from January 1998 through December 2000 from the Journal of Family Practice, the Journal of Family Medicine, the Annals of Emergency Medicine, the Journal of Academic Emergency Medicine. Articles from January 2000 through December 2000 of Obstetrics and Gynecology and the American Journal of Obstetrics and Gynecology were also included. Case reports and editorials were not included in this analysis. There were a total of 1828 articles reviewed (666 from Emergency Medicine articles, 380 from Family Practice, and 782 from Obstetrics and Gynecology). The distribution of study types (cross-sectional or survey, retrospective, or prospective) did not differ between the selected journals within Emergency Medicine, Family Practice, or Obstetrics and Gynecology. Pearson's chi-square/Fisher's Exact test was the statistic of choice overall (47.5%) followed by Student's t-test (33.1%). Analysis-of-variance was used in 23.3% of the studies, nonparametric methods (8.1%), linear regression (17.6%), and odds ratios/logistic regression (17.4%). Other statistical procedures were used less than 10% of the time. These results show that a physician who comfortably comprehends the appropriate use of descriptive statistics Student's t-test, Pearson's chi-square/Fisher's Exact test will be able to read and interpret at least 70% of the published medical literature. Educational efforts should focus on appropriate study design and analysis.

Clinical Competence↗
PubMed1985

Effect of nonsurgical periodontal therapy. V. Patterns of probing attachment loss in non-responding sites.

Incisors, cuspids and premolars in 33 patients with advanced chronic periodontitis were treated by plaque control and 1 single episode of supra- and subgingival debridement. The results were monitored by probing attachment level measurements for 6 sites of each tooth every 3rd month during a period of 24 months. A total of 1368 sites were observed. From these were selected 280 "non-responding" sites showing 1.0 mm or more loss of probing attachment at 24 months compared to baseline. Scatter diagrams of the sequence of 9 probing attachment recordings obtained during the 24-month study were produced for each of these 280 sites. Study of these scatter diagrams resulted in identification of 7 different patterns of probing attachment change over time. A linear pattern of gradual loss of probing attachment throughout the 24-month observation period was found for 73% of the non-responding sites. Of the less frequently seen patterns, 3 approximated a linear course and 3 were non-linear. Linear analysis of regression as a statistical method to determine attachment loss for individual sites seems to be suitable for sites with linear patterns and for sites approximating a linear pattern. The insensitivity of regression analysis in non-linear patterns may be acceptable if a cautious analysis is warranted.

Adult↗
PubMed1998

Comparison of multiple prediction models for ambulation following spinal cord injury.

Few studies have properly compared predictive performance of different models using the same medical data set. We developed and compared 3 models (logistic regression, neural networks, and rough sets) in the in prediction of ambulation at hospital discharge following spinal cord injury. We used the multi-center Spinal Cord Injury Model System database. All models performed well and had areas under the receiver operating characteristic curve in the 0.88-0.91 range. All models had sensitivity, specificity, and accuracy greater than 80% at ideal thresholds. The performance of neural network and logistic regression methods was not statistically different (p = 0.48). The rough sets classifier performed statistically worse than either the neural network or logistic regression models (p-values 0.002 and 0.015 respectively).

Acute Disease↗
PubMed2005

Mortality from lung cancer and tobacco smoking in Ohio (U.S.): will increasing smoking prevalence reverse current decreases in mortality?

BACKGROUND: Despite significant changes in smoking patterns within the past few decades, lung cancer remains a major cause of cancer deaths in many developed countries in people of each sex, and one of the most important public health issues. The study aims to analyze the possible impact of changes in tobacco smoking practices in the state of Ohio (U.S.) on current and future trends and patterns of lung cancer mortality. MATERIALS AND METHODS: Mortality rates from lung cancer were calculated for the period 1970 to 2001 on the basis of data from the National Center for Health Statistics. The Joinpoint regression approach was used to evaluate changes in time trends by sex, age, and race. Data on smoking prevalence in Ohio were retrieved from the Centers for Disease Control and Prevention website. RESULTS: Lung cancer mortality rates in Ohio have declined among men of all ages as well as in specific age groups in the 1990s, and the rate of increase among middle-aged and elderly women has dropped over time. The mortality rate among young women (ages 20-44) began to increase during the early 1990s. The prevalence of smoking in Ohio has increased since the early 1990s, especially among young persons. CONCLUSIONS: Recent trends in tobacco smoking in Ohio indicate that the declining trends in lung cancer mortality might be reversed in the future. An early indicator of possible change is the recent increase in mortality among young women. Implementation of the Ohio Comprehensive Tobacco Use Prevention Strategic Plan might help to disseminate proven prevention strategies among the inhabitants of Ohio and might thus prevent future increases in lung cancer mortality rates in the state.

Adult↗
PubMed2000

Profile of an orthodontic patient at risk of dental trauma.

Increased overjet and inadequate lip coverage of the maxillary incisors are considered significant risk factors in many clinical studies. The purpose of the present study was to examine this issue of dental injury by actual cephalometric measurements in orthodontic patients. Pretreatment cephalograms (taken with lips in repose) of consecutive patients were used. The patients were allotted to two groups Group T (trauma): 56 patients who had injured their maxillary incisors prior to their orthodontic treatment, mean age at the start of treatment 11.9 years (SD = 1.5); and Group C (control): 98 patients with intact maxillary incisors, mean age at the start of treatment 11.6 years (SD = 1.3). Twelve cephalometric landmarks on the soft and hard tissue profile were identified and digitized and the relevant dental, skeletal and soft tissue measurements recorded. The variables in Groups T and C were compared and their predictive values for possible occurrence of trauma were tested by logistic regression analysis. No statistically significant differences between boys and girls were found. Overjet or maxillary incisor exposure or interlabial gap, each as a single variable, could differentiate between the two groups. Logistic regression analysis indicated that only a small percentage (28.7%) of the dependent variable variation (trauma vs control) can be explained by interlabial gap, gender, upper incisor long axis to facial plane (degree), upper incisor long axis to interlabial gap and overjet.

Cephalometry↗
PubMed1997

Regression calibration method for correcting measurement-error bias in nutritional epidemiology.

Regression calibration is a statistical method for adjusting point and interval estimates of effect obtained from regression models commonly used in epidemiology for bias due to measurement error in assessing nutrients or other variables. Previous work developed regression calibration for use in estimating odds ratios from logistic regression. We extend this here to estimating incidence rate ratios from Cox proportional hazards models and regression slopes from linear-regression models. Regression calibration is appropriate when a gold standard is available in a validation study and a linear measurement error with constant variance applies or when replicate measurements are available in a reliability study and linear random within-person error can be assumed. In this paper, the method is illustrated by correction of rate ratios describing the relations between the incidence of breast cancer and dietary intakes of vitamin A, alcohol, and total energy in the Nurses' Health Study. An example using linear regression is based on estimation of the relation between ultradistal radius bone density and dietary intakes of caffeine, calcium, and total energy in the Massachusetts Women's Health Study. Software implementing these methods uses SAS macros.

Adult↗
PubMed1990

Using logistic regression in perinatal epidemiology: an introduction for clinical researchers. Part 1: Basic concepts.

Logistic regression is a statistical modelling technique which may be applied to estimate the simultaneous effect of a set of predictors (e.g. gestational age, birthweight) on the risk of a certain outcome variable (e.g. neonatal death) which can take either one of two possible values (yes/no, alive/dead) or in the situation where one wants to estimate the effect of a particular risk factor (e.g. sex) while adjusting (correcting) for the effect of other risk factors (e.g. gestational age). Since this situation often occurs both in medical or epidemiological research and in daily practice it is important to have a flexible and readily interpretable technique to predict risk of mortality and morbidity. Since the logistic regression technique is a powerful and widely applicable tool which is appearing more and more often in the epidemiological literature, a basic understanding of this technique becomes necessary for the clinical researcher. In this paper we explain logistic regression to medical researchers who do not have any particular statistical background. Part 1 covers the basic concepts. Part 2 will describe the actual representation of the basic concepts in a logistic framework.

Epidemiologic Methods↗
PubMedDate not supplied

Definition of a responder: analysis of behavioral, cardiovascular, and endocrine responses to varied workload in air traffic controllers.

Individual differences in behavioral, cardiovascular, and endocrine responses to varying workload among 381 air traffic controllers were assessed using random regression modeling. Although most men showed significant increases in behavioral arousal associated with increasing planes, there were major individual differences in response in systolic and diastolic blood pressure, heart rate, and cortisol. Approximately 20% to 25% of those studied had large increases in each of these domains, along with a smaller group showing inverse responses in heart rate and cortisol. There was also evidence of a smaller number of enhanced responders within the highest groups, who tended to have more missing values at higher levels of workload. There was convergence in the definition of responders using three statistical strategies: random regression, correlational analyses, and ANOVA. Response in one physiological/behavioral domain was essentially independent of response in another, supporting the conclusion of specificity, rather than a global tendency to respond to increasing work load.

Adult↗
PubMed2003

Discordance rate, a new concept for combining diagnostic decisions with analytical performance characteristics. 1. Application in method or sample system comparisons and in defining decision limits.

Method comparison studies are usually evaluated by several statistical tests (e.g., regression analysis) which sufficiently describe the analytical (dis)agreement between the results of two procedures. However, they do not provide any information how differences, if observed, influence diagnostic decision making. A novel statistical approach is described to test the clinical relevance of differences between two analytical procedures. The new procedure requires a population-based probability which describes the distribution of values within the population under study and an analytical probability quantifying the risk of errors due to replacing one method by the other. The population probability was derived from 171 subjects from two outpatient departments (internal medicine and dermatology) who were subjected to an oral glucose tolerance test because type 2 diabetes mellitus was suspected. The analytical probability was determined from duplicate glucose measurements in venous and capillary blood, and venous plasma in the fasting and 2 h post-challenge state by the routine method used in a central laboratory (Ebio analyzer) and a (POCT) glucometer (Elite). The two probabilities were combined into one "error rate" (discordance rate). The new concept was applied to three examples. In the first example, a comparison between two analytical systems led to discordance rates above 15%. After transforming the Elite analyzer results by a regression function, the discordance rate decreased below 5%, which was considered to be acceptable for the diagnostic purpose studied. In the second example, discordance rates were estimated by comparing different sample systems with each other. The use of whole blood in comparison with venous plasma led to discordance rates of 5-7% for venous blood and 7-10% for capillary blood. The same data set was also used in a third example to derive decision limits for capillary and venous blood from the established plasma values. The proposed procedure estimates the diagnostic error rate based on analytic performance characteristics and population probabilities. It extends the concept of (un)efficiency by including the effect of variability about a decision limit and the distribution of the measurement values in the patient population.

Blood Glucose↗