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At least 307 records · Page 17Linked to original sources

PubMed1992

Surveillance data on US coal miners' pneumoconiosis, 1970 to 1986.

OBJECTIVES: Statistics on prevalence of pneumoconiosis among working underground coal miners from data collected as part of a large national radiographic surveillance program between 1970 and 1986 are presented. The main intent was to examine the time-related trend in prevalence over this period, which coincides with historically low dust levels mandated by federal act. METHODS: Tenure-specific prevalence rates and summary statistics derived from them for four consecutive time intervals within the 16-year period were calculated and compared. RESULTS: The results indicate a reduction in pneumoconiosis over the life of the program. This trend is similar to that seen in epidemiologic studies undertaken concurrently. CONCLUSIONS: Although low participation in the surveillance program and other problems complicate the findings, it appears that reductions in dust exposure mandated by federal act in 1969 have led to lower prevalence of pneumoconiosis among underground coal miners.

Bias↗

PubMed1989

Statistical analysis in clinical laboratory medicine: fundamentals and common uses.

Medical research studies may be classified into two broad categories: descriptive and inferential. Descriptive studies are intended to describe the characteristics of only the study group, using observations obtained from every member of the group. Inferential studies, on the other hand, are designed to enable the investigator to use observations from selected individuals (a sample) to make conclusions about the larger group (population) from which they were drawn. The first part of this paper deals with descriptive studies, focusing on summary statistics and graphic techniques. The remainder deals with inferential studies. We start by describing how characteristics of the population may be estimated from characteristics of a small number of its members, which are randomly selected. These principles are then applied to the problem of testing hypotheses about the population by use of some of the more common testing procedures. These include t tests, regression, chi-square tests, evaluating a new diagnostic procedure, estimating normal values, survivorship studies, and sequential methods.

Data Interpretation, Statistical↗

PubMedDate not supplied

Summarizing methacholine bronchoprovocation data in epidemiological surveys.

We have performed bronchoprovocation tests with methacholine in 41 patients with asthma due to Western red cedar dust and in 56 office-workers without known respiratory illness. Our purpose was to define a summary statistic for useful bronchial hyperresponsiveness in epidemiologic surveys. We found a significant linear relationship between the concentration of methacholine and the FEV1 response. We noted, in addition, a positive relation between the rate of the FEV1 response per concentration and the level of FEV1. We conclude that a linear dose-response slope, which can be calculated for each individual, provides a comprehensive summary of methacholine bronchoprovocation tests and is useful in epidemiologic surveys.

Adult↗

PubMed2026

Dissecting the shared genetic architecture between migraine subtypes and cardiovascular diseases: a multi-layered genomic analysis.

BACKGROUND: Epidemiological studies have linked migraine to an increased risk of cardiovascular disease (CVD); however, the shared genetic basis and putative causal relationships between migraine subtypes and cardiovascular traits remain poorly understood. METHODS: Leveraging large-scale GWAS summary statistics for migraine phenotypes (overall migraine, migraine with aura [MA], and migraine without aura [MO]) from FinnGen R12, along with seven cardiovascular diseases from publicly available consortia, we conducted a multi-layered genetic analysis. This integrative framework encompassed genetic correlation [linkage disequilibrium score regression (LDSC) and high-definition likelihood (HDL)], cross-trait meta-analysis (CPASSOC and PLACO), Bayesian colocalization, summary-data-based Mendelian randomization (SMR) using GTEx v8 eQTL data, and bidirectional two-sample Mendelian randomization (MR). RESULTS: Significant genetic correlations were identified between migraine and multiple cardiovascular traits, with hypertension and coronary artery disease (CAD) showing the most robust associations. MA exhibited broader genetic overlap with cardiovascular diseases than MO, including a notably stronger correlation with ischemic stroke, whereas MO demonstrated a stronger correlation with hypertension. Cross-trait meta-analysis identified 160 pleiotropic loci across 17 of 21 trait pairs. Colocalization analysis confirmed 32 loci harboring shared causal variants, mapped to 13 candidate genes, of which 7 (PHACTR1, LRP1, SOX7, ABO, FHOD3, MEI1, XKR6) were further validated by SMR as exhibiting tissue-specific regulatory effects. Among these, PHACTR1 displayed the broadest pleiotropic profile across migraine phenotypes and vascular diseases. After MR-PRESSO outlier removal, bidirectional MR identified 10 MR-supported associations, two of which (genetic liability to hypertension on overall migraine, and CAD on MA) survived Bonferroni correction, all free of detectable horizontal pleiotropy. Genetic liability to hypertension was associated with increased migraine risk (OR = 1.90, 95% CI 1.25-2.90, P = 2.64 × 10⁻³), atherosclerotic diseases showed subtype-specific effects (inverse for MO, positive for MA), and, in the reverse direction, migraine was associated with increased ischemic stroke risk. CONCLUSIONS: This study provides a comprehensive and systematic characterization of the shared genetic architecture between migraine subtypes and cardiovascular diseases. By identifying pleiotropic genes and bidirectional putative causal relationships with subtype-specific patterns, our findings carry implications for the development of targeted therapeutics and subtype-specific cardiovascular risk stratification.

Humans↗

PubMed1994

[Demographic statistics after the GBA Law is passed].

"The Dutch Ministry of Internal Affairs plans to replace the old written population systems on paper with a new system of decentralized automated population registers (in Dutch this system is called: GBA) on 1 October 1994.... In the summer of 1993 Statistics Netherlands carried out a test to find out whether the GBA messages are appropriate for making population statistics. To do this such messages were forwarded to Statistics Netherlands by five municipalities for three months. The conclusion of the test results was that the GBA system is technically adequate for making population statistics." (SUMMARY IN ENG)

Data Collection↗

PubMed2005

Profiling the New Zealand Thoroughbred racing industry. 1. Training, racing and general health patterns.

AIM: To describe patterns in training, racing, and general health in a population of Thoroughbred racehorses in New Zealand. METHODS: A longitudinal study was designed to collect data on horses training under the care of 20 selected trainers from 20 different stables and five regional training venues in the mid to lower regions of the North Island. Data were collected from trainers at approximately monthly intervals between October 1997 and July 2000, and electronic data containing race and trial results for all starts in New Zealand for the same time period were obtained from New Zealand Thoroughbred Racing (NZTR). Summary statistics were used to describe patterns present in the data. Horse training days and study days were used as the denominator horse-time-at-risk for incidence rate estimations, and counts of horses and events used to derive proportions and cumulative incidence estimates. Simple statistical comparisons were completed using parametric and non-parametric procedures. RESULTS: Twenty trainers provided information on 1,571 horses, 554,745 horse study days, and 9,963 starts in official trials or races. Males comprised 50.2% of all horses. Although females contributed more study days for 2-, 3- and 4-year-olds, males contributed more study days in horses aged > or =5 years. Horses spent an average of 71% of their time in training and the remaining 29% in spell periods. Duration of training preparations and spell periods was associated with horse age and the reason for a spell. Most horses began a training preparation doing slow work and then progressively advanced to a first start by 68 days after the start of a training preparation. Incidence rate estimates for starts, training days to first start, and training days between successive starts in the same preparation, are presented. Horses completed 2.5 starts per 100 training days with a median of 17 days between successive starts for the same horse. CONCLUSION: This study provides summary information on training, racing and general health patterns in Thoroughbred racehorses in the North Island of New Zealand. Although limited to simple comparisons and descriptive statistics, these results may contribute to the identification and prioritization of issues facing the racing industry in New Zealand.

Animal Husbandry↗

PubMed1992

Epidemiological data on US coal miners' pneumoconiosis, 1960 to 1988.

OBJECTIVES: Statistics on prevalence of pneumoconiosis among working underground coal miners based on epidemiologic data collected between 1960 and 1988 are presented. The main intent was to examine the time-related trend in prevalence, particularly after 1969, when substantially lower dust levels were mandated by federal act. METHODS: Data from studies undertaken between 1960 and 1968 were collected and compared. Information for the period 1969 to 1988 was extracted from a large ongoing national epidemiologic study. Tenure-specific prevalence rates and summary statistics derived from the latter data for four consecutive time intervals within the 19-year period were calculated and compared. RESULTS: The results indicate a reduction in pneumoconiosis over time. The trend is similar to that seen in a large radiologic surveillance program of underground miners operated concurrently. CONCLUSIONS: Although such factors as x-ray reader variation, changes in x-ray standards, and worker self-selection for examination may have influenced the findings to some extent, adjusted summary rates reveal a reduction in prevalence concurrent with reductions in coal mine dust levels mandated by federal act in 1969.

Adult↗

PubMed1999

Exposure to risk factors for ulcerative colitis occurs during an early period of life.

OBJECTIVE: It has been speculated that environmental factors play a role in the etiology of ulcerative colitis. A previous analysis revealed that the time trends of ulcerative colitis in England were shaped by an underlying birth-cohort pattern. We undertook this study to test whether the birth-cohort pattern was a unique feature of the English vital statistics or whether a similar phenomenon could also be ascertained in the mortality statistics from a different country, such as Switzerland. Besides comparing the data of ulcerative colitis from Switzerland and England, the trends of ulcerative colitis were compared with those of gastric and duodenal ulcer. METHODS: Death rates from ulcerative colitis, gastric ulcer, and duodenal ulcer were plotted against the period of death and period of birth. An age-standardized cohort mortality ratio was calculated as a summary statistic of the overall mortality associated with each consecutive birth-cohort. RESULTS: Mortality from ulcerative colitis increased among successive generations born throughout the 19th century. It peaked in individuals born around 1890 and has declined since then. Strikingly similar patterns were found in Switzerland and England. The birth-cohort pattern underlying the time trends of ulcerative colitis applied equally to the data for women and men. In comparison with peptic ulcer, the birth-cohort pattern of ulcerative colitis was almost identical to that of duodenal ulcer. It peaked in both countries 10-20 yr later than gastric ulcer. CONCLUSIONS: The birth-cohort pattern indicates that acquisition of ulcerative colitis is strongly influenced by environmental risk factors and that the exposure to these factors occurs during an early period of life. The similarity in the birth-cohort patterns of duodenal ulcer and ulcerative colitis could hint at a childhood infection or a related mode of transmission in both diseases.

Adult↗

PubMed1997

Application and evaluation of the kappa statistic in the design and interpretation of chiropractic clinical research.

The Kappa statistic (K) is becoming more widely used in chiropractic clinical research. Although the calculation of K is straightforward, assumptions made regarding the acquisition and interpretation of data require serious consideration before conclusions regarding the final outcome can be made. Of particular interest is the application of K for the interpretation of validity and reliability. In this regard, I argue against the use of K as a summary statistic. I present here a description of K as a function of observer agreement (P(o)), without which K has little meaning, and show how a knowledge of this function should direct the design and, therefore, the interpretation of chiropractic clinical research. Only when all concerns regarding experimental design are either addressed directly or compensated for in the analysis can interpretations be made regarding validity or reliability. Lacking such attention, K becomes an indicator of experimental design rather than an indicator of validity or reliability.

Chiropractic↗

PubMed2004

Prior convictions: Bayesian approaches to the analysis and interpretation of clinical megatrials.

Large, randomized clinical trials ("megatrials") are key drivers of modern cardiovascular practice, since they are cited frequently as the authoritative foundation for evidence-based management policies. Nevertheless, fundamental limitations in the conventional approach to statistical hypothesis testing undermine the scientific basis of the conclusions drawn from these trials. This review describes the conventional approach to statistical inference, highlights its limitations, and proposes an alternative approach based on Bayes' theorem. Despite its inherent subjectivity, the Bayesian approach possesses a number of practical advantages over the conventional approach: 1). it allows the explicit integration of previous knowledge with new empirical data; 2). it avoids the inevitable misinterpretations of p values derived from megatrial populations; and 3). it replaces the misleading p value with a summary statistic having a natural, clinically relevant interpretation-the probability that the study hypothesis is true given the observations. This posterior probability thereby quantifies the likelihood of various magnitudes of therapeutic benefit rather than the single null magnitude to which the p value refers, and it lends itself to graphical sensitivity analyses with respect to its underlying assumptions. Accordingly, the Bayesian approach should be employed more widely in the design, analysis, and interpretation of clinical megatrials.

Bayes Theorem↗

PubMed1991

Use of dairy herd improvement monthly summary data to monitor intervention strategies in a dairy herd experiencing suboptimal reproductive performance and reduced milk production.

An 87-cow dairy herd with a history of high milk production was visited because of reduced reproductive performance and decreasing milk production. Cows that had recently delivered calves were thin, and many cows had evidence of previous episodes of laminitis. A ration that provided an unfavorable forage-to-concentrate ratio was being fed. In addition to various diagnostic efforts, management changes that were made included alteration of the ration and installation of a computer-operated feeder. After the initial visit, the herd was monitored for 30 months by the use of Dairy Herd Improvement monthly herd summary data. Several potential strengths and weaknesses of using selective production and reproduction monthly summary statistics were illustrated by this study. Milk production, as monitored by mature-equivalent production and average relative value-milk, continued to increase throughout the 30 months after intervention. Reproductive performance, as indicated by first-service conception rate, did not begin to improve until the final 6 months of the monitoring period. Overall, in addition to assisting in diagnostic efforts. Dairy Herd Improvement monthly herd summary data may be used to establish goals, provide comparisons, and maintain producer interest after practitioner intervention in herd management.

Animal Feed↗

PubMed2006

Preliminary observations on the calcaneal trabecular microarchitecture of extant large-bodied hominoids.

In this pilot study, we point out potential differences between calcaneal trabecular microarchitecture in humans and nonhuman large apes, such as increased degree of anisotropy, reduced bone volume fraction, and very stereotypical orientation of the trabeculae. Even though sample size does not permit us to investigate the issue statistically, the observed differences between humans and other hominoids warrants further in-depth investigation. We also show that some measurements of the trabecular network might be dependent on sampling density, which can be difficult to deal with in the case of animals of different body masses. We also present a new visualization technique that summarizes the trabecular network orientation, and makes it more readily interpretable than the summary statistics of the underlying fabric tensor of the orientation matrix.

Animals↗

PubMed2000

Should calcaneal fractures be treated surgically? A meta-analysis.

A MEDLINE search from 1980 through 1996 revealed 1845 articles dealing with calcaneal fractures. Six of these articles that compared operative versus nonoperative treatment for displaced calcaneal fractures met the minimum criteria for inclusion in a meta-analysis. A statistical summary of information across the six articles revealed a trend for surgically treated patients to be more likely to return to the same type of work as compared with nonoperatively treated individuals. There also was a trend for nonoperatively treated patients to have a higher risk of experiencing severe foot pain than did operatively treated patients. Unfortunately, none of the other outcomes could be summarized formally across studies using statistical techniques because of variability in reporting across studies. Although the tendency was always for operatively treated patients to have better outcomes (reaching statistical significance in some of the articles), the strength of evidence to recommend operative treatment for displaced intraarticular calcaneal fractures remains weak. A large prospective randomized controlled trial should be able to answer this question.

Calcaneus↗

PubMed2006

Development and application of a methodology for determining background groundwater quality at the Savannah River Site.

A statistical methodology formulated for defining background or baseline levels of constituents of concern in groundwater is presented. The methodology was developed for the case where prior delineation of unimpacted areas is not possible because of site history and a large set of groundwater monitoring measurements exists. Consideration was given to spatial and temporal trends, outliers, and final segregation of wells into impacted or unimpacted categories to develop probability distributions and summary statistics for each constituent evaluated. The formulated approaches were applied to groundwater monitoring data for the U.S. Department of Energy Savannah River Site facility, and results for four representative constituents (aluminum, arsenic, mercury, and tritium) are discussed.

Aluminum↗

PubMed2002

Models for microarray gene expression data.

This paper describes a general methodology for the analysis of differential gene expression based on microarray data. First, we characterize the data by a linear statistical model that accounts for relevant sources of variation in the data and then we consider estimation of the model parameters. Because microarray studies typically involve thousands of genes, we propose a two-stage method for parameter estimation. The interaction terms for genes and experimental conditions in this model capture all relevant information about differential gene expression in the microarray data. We propose a mixture distribution model for a summary statistic of differential expression that consists of null and alternative component distributions. The mixture model suggests two methods for identifying genes exhibiting differential expression. One is a frequentist method that identifies distinguished genes and the other an empirical Bayes procedure that yields estimated posterior probabilities of differential expression, conditional on observed microarray readings.

Animals↗

PubMedDate not supplied

Assessing the clinical benefits of erythropoietic agents using area under the hemoglobin change curve.

INTRODUCTION: In assessing erythropoietic agents for chemotherapy-induced anemia, traditional single time-point end points (e.g., hematopoietic response [HR]) fail to reflect clinical benefits over the entire therapy course. Area under the hemoglobin change curve (Hb AUC) is introduced as an alternative measure, and its reliability, clinical significance, and superiority are assessed. METHODS: Using data from a phase IV open-label epoetin alfa (EPO) trial, we tested Hb AUC reliability by comparing its values derived from primary patient data with those derived from aggregated data. Clinical significance of the Hb AUC was investigated in three phase IV EPO trials by examining the linear relationship between Hb AUC quartiles and established clinical end points. The superiority of the Hb AUC over HR in its association with blood transfusion was tested through logistic regressions and area under the receiver operating characteristic (ROC) curve analysis. RESULTS: The Hb AUC values derived from patient and aggregated data were similar. Strong and statistically significant linear trends of decreasing transfusion requirements, increasing quality-of-life improvements, and decreasing time to HR were found across Hb AUC quartiles. The Hb AUC rendered the HR variable insignificant when both were present in the same model. Area under the ROC curve analysis supported the superior performance of the Hb AUC. CONCLUSIONS: We found that the Hb AUC is an objective, reliable, clinically meaningful, and comprehensive summary statistic that may be used to quantify clinical benefits for patients receiving erythropoietic agents. Further prospective validation of the Hb AUC metric is recommended.

Anemia↗

PubMed2004

[Relevance of design and structure of data-bases in research].

Research studies require a methodological frame providing concepts and approach procedures. The so-called scientific method encompasses systematic data collection and problem solving notions. Epidemiology and statistics are essential disciplines in this process. The goal of this course is to provide knowledge for design of databases, with special attention to the definition of variables and to measurement scales. A small database on headache is made using fictitious information. A questionnaire designed for this purpose is used as a foundation. Finally, we present a graphic design on the percentage distribution of the variable gender, as an example of the summary statistics.

Databases as Topic↗

PubMed2001

Initial experience with use of tris-acryl gelatin microspheres for uterine artery embolization for leiomyomata.

PURPOSE: To assess the safety and effectiveness of tris-acryl gelatin microspheres (Embospheres) in the treatment of leiomyomata by uterine artery embolization. MATERIALS AND METHODS: This was a Phase I study of 30 patients with symptomatic leiomyomata. Each patient underwent ultrasound imaging and completed questionnaires regarding symptoms and health status at baseline and 3 and 6 months after treatment. Bilateral embolization was performed with use of tris-acryl gelatin microspheres. Summary statistics were used to characterize the demographic and procedure data. Paired t-tests were used to assess change in the severity of menstrual bleeding and health-related quality of life. RESULTS: Bilateral embolization was technically successful in all patients. Three months after treatment, menstrual bleeding was markedly improved as assessed by menorrhagia questionnaire (P <.0001) and menstrual calendar (P <.0001). Pelvic pain and discomfort was improved in 92% of cases. Physical component summary scores of the SF-12 also increased from baseline at 3 months (P =.02) and at 6 months (P =.01). Minor complications occurred in nine patients; there were no major complications. CONCLUSION: Although limited, this initial experience suggests that tris-acryl gelatin microspheres are an effective and safe embolic agent for the treatment of uterine leiomyomata.

Adult↗