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Substantial Heterogeneity (substantial + heterogeneity)

Distribution by Scientific Domains

Medical Sciences	60%
Humanities and Social Sciences	13%

Selected Abstracts

Bone Strength at Clinically Relevant Sites Displays Substantial Heterogeneity and Is Best Predicted From Site-Specific Bone Densitometry

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2002
Felix Eckstein Ph.D.
Abstract In this study we test the hypotheses that mechanical bone strength in elderly individuals displays substantial heterogeneity among clinically relevant skeletal sites, that ex situ dual-energy X-ray absorptiometry (DXA) provides better estimates of bone strength than in situ DXA, but that a site-specific approach of bone densitometry is nevertheless superior for optimal prediction of bone failure under in situ conditions. DXA measurements were obtained of the lumbar spine, the left femur, the left radius, and the total body in 110 human cadavers (age, 80.6 ± 10.5 years; 72 female, 38 male), including the skin and soft tissues. The bones were then excised, spinal and femoral DXA being repeated ex situ. Mechanical failure tests were performed on thoracic vertebra 10 and lumbar vertebra 3 (compressive loading of a functional unit), the left and right femur (side impact and vertical loading configuration), and the left and right distal radius (fall configuration, axial compression, and 3-point-bending). The failure loads displayed only very moderate correlation among sites (r = 0.39 to 0.63). Ex situ DXA displayed slightly higher correlations with failure loads compared with those of in situ DXA, but the differences were not significant and relatively small. Under in situ conditions, DXA predicted 50-60% of the variability in bone failure loads at identical (or closely adjacent) sites, but only around 20-35% at distant sites, advocating a site-specific approach of densitometry. These data suggest that mechanical competence in the elderly is governed by strong regional variation, and that its loss in osteoporosis may not represent a strictly systemic process. [source]

Comparison of the effects of treatment of peri-implant infection in animal and human studies: systematic review and meta-analysis

CLINICAL ORAL IMPLANTS RESEARCH, Issue 2 2010
Clovis Mariano Faggion Jr
Abstract Objective: The main objective of this systematic review is to compare the effects of treatment of peri-implant infection between animal and human studies. Material and methods: A literature search was conducted using the Medline, Cochrane Central Register of Controlled Trials, and Latin American and Caribbean Health Sciences Literature databases up to and including May 2008. In addition, bibliographies of systematic reviews on peri-implant diseases were searched manually. Non-surgical and surgical treatments of peri-implantitis/mucositis in animal models or human studies were compared. Meta-analysis was conducted to investigate the difference between the reported treatment effects in animal and human studies. Changes in probing pocket depth (PPD) and probing attachment level (PAL) from baseline measurements were used as measures of outcome. Single-level and multilevel meta-regression analysis was performed by taking into account the different follow-up times of the studies included. Results: The single-level and multilevel random-effects meta-analysis showed that the difference in PPD reduction [0.31 mm, 95% confidence interval (CI): ,0.27, 0.88] and in PAL gain (0.21 mm, 95% CI: ,0.47, 0.88) between animal and human studies was not statistically significant. The random-effects meta-regression suggested that studies with longer follow-up times revealed greater PPD reduction (0.25 mm per month, 95% CI: 0.14, 0.35). However, when the different follow-up times were taken into account, these differences became greater. Substantial heterogeneity between studies was found in the meta-analyses (I2=97.6% for animal studies and 99.9% for human studies). Conclusion: There was great heterogeneity between human and animal studies in terms of study designs and treatment procedures. Therefore, the results from this meta-analysis should be interpreted with caution. Heterogeneity between studies and its causes merit further investigations. To cite this article: Faggion CM Jr, Chambrone L, Gondim V, Schmitter M, Tu Y-K. Comparison of the effects of treatment of peri-implant infection in animal and human studies: systematic review and meta-analysis. Clin. Oral Impl. Res. 21, 2010; 137,147. doi: 10.1111/j.1600-0501.2009.01753.x [source]

The influence of poorly interconnected fault zone flow paths on spring geochemistry

GEOFLUIDS (ELECTRONIC), Issue 2 2008
J. C. ROWLAND
Abstract Thermal springs commonly occur along faults because of the enhanced vertical permeability afforded by fracture zones. Field and laboratory studies of fault zone materials document substantial heterogeneities in fracture permeabilities. Modeling and field studies of springs suggest that spatial variations in permeability strongly influence spring locations, discharge rates and temperatures. The impact of heterogeneous permeability on spring geochemistry, however, is poorly documented. We present stable isotope and water chemistry data from a series of closely spaced thermal springs associated with the Hayward Fault, California. We suggest that substantial spatial variations observed in ,18O and chloride values reflect subsurface fluid transport through a poorly connected fracture network in which mixing of subsurface waters remains limited. Our measurements provide insight into the effect of fracture zone heterogeneities on spring geochemistry, offer an additional tool to intuit the nature of tectonically induced changes in fault zone plumbing, and highlight the need to consider local variations when characterizing fracture zone fluid geochemistry from spring systems with multiple discharge sites. [source]

The effectiveness of brief alcohol interventions in primary care settings: A systematic review

DRUG AND ALCOHOL REVIEW, Issue 3 2009
EILEEN F. S. KANER
Abstract Issues. Numerous studies have reported that brief interventions delivered in primary care are effective in reducing excessive drinking. However, much of this work has been criticised for being clinically unrepresentative. This review aimed to assess the effectiveness of brief interventions in primary care and determine if outcomes differ between efficacy and effectiveness trials. Approach. A pre-specified search strategy was used to search all relevant electronic databases up to 2006. We also hand-searched the reference lists of key articles and reviews. We included randomised controlled trials (RCT) involving patients in primary care who were not seeking alcohol treatment and who received brief intervention. Two authors independently abstracted data and assessed trial quality. Random effects meta-analyses, subgroup and sensitivity analyses and meta-regression were conducted. Key Findings. The primary meta-analysis included 22 RCT and evaluated outcomes in over 5800 patients. At 1 year follow up, patients receiving brief intervention had a significant reduction in alcohol consumption compared with controls [mean difference: ,38 g week,1, 95%CI (confidence interval): ,54 to ,23], although there was substantial heterogeneity between trials (I2 = 57%). Subgroup analysis confirmed the benefit of brief intervention in men but not in women. Extended intervention was associated with a non-significantly increased reduction in alcohol consumption compared with brief intervention. There was no significant difference in effect sizes for efficacy and effectiveness trials. Conclusions. Brief interventions can reduce alcohol consumption in men, with benefit at a year after intervention, but they are unproven in women for whom there is insufficient research data. Longer counselling has little additional effect over brief intervention. The lack of differences in outcomes between efficacy and effectiveness trials suggests that the current literature is relevant to routine primary care. [Kaner EFS, Dickinson HO, Beyer F, Pienaar E, Schlesinger C, Campbell F, Saunders JB, Burnand B, Heather N. The effectiveness of brief alcohol interventions in primary care settings: A systematic review. Drug Alcohol Rev 2009;28:301,323] [source]

Assessing sources of variability in measurement of ambient particulate matter

ENVIRONMETRICS, Issue 6 2001
Michael J. Daniels
Abstract Particulate matter (PM), a component of ambient air pollution, has been the subject of United States Environmental Protection Agency regulation in part due to many epidemiological studies examining its connection with health. Better understanding the PM measurement process and its dependence on location, time, and other factors is important for both modifying regulations and better understanding its effects on health. In light of this, in this paper, we will explore sources of variability in measuring PM including spatial, temporal and meteorological effects. In addition, we will assess the degree to which there is heterogeneity in the variability of the micro-scale processes, which may suggest important unmeasured processes, and the degree to which there is unexplained heterogeneity in space and time. We use Bayesian hierarchical models and restrict attention to the greater Pittsburgh (USA) area in 1996. The analyses indicated no spatial dependence after accounting for other sources of variability and also indicated heterogeneity in the variability of the micro-scale processes over time and space. Weather and temporal effects were very important and there was substantial heterogeneity in these effects across sites. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Contributions of genetic and environmental components to changes in phenotypic variation between generations

JOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 4 2010
A. Wolc
Summary We evaluate the extent to which changes in phenotypic variation among generations of populations kept in the same environment are due to changes in genetic (VA) or in environmental (VE) variance. Data were available on body weight of adult poultry on a total of 89186 birds (mainly females) from six generations of each of seven lines of layers. There was substantial heterogeneity of variation between generations, shown to be in both VA and VE components. Based on the Akaike information criterion (AIC), the best fit was with both components changing, and a better fit was obtained if VA/VE (i.e. heritability) or VE, rather than VA, was assumed constant. In analyses of quantitative genetic data spanning environmental groups, attention should be paid to whether and how the variance components change among groups before undertaking detailed variance partition that may be sensitive to such changes. [source]

Bone Strength at Clinically Relevant Sites Displays Substantial Heterogeneity and Is Best Predicted From Site-Specific Bone Densitometry

Constraints to expanding access to health interventions: an empirical analysis and country typology

JOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 1 2003
M. Kent Ranson
This paper adopts three approaches to classifying countries by level of constraint, in order to inform the choice of strategies for expanding access to health interventions in different contexts. We find substantial heterogeneity across the 84 low-income and (all) sub-Saharan African countries analysed. Poor sub-Saharan African countries are the most highly constrained; Asian countries, in general, less constrained; and the two Asian giants, China and India, consistently fall above the median. Former Soviet Union countries rank low in terms of governance, but high for health systems variables. Only 10 per cent of the total population of the countries included lives in countries with the greatest constraints. The potential applications of the analysis are discussed, as are the limitations of the cross-sectional, macro level approach. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Cisapride treatment for gastro-oesophageal reflux in children: A systematic review of randomized controlled trials

JOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 6 2000
R E Gilbert
Abstract: The aim of the systematic review was to determine the effect of cisapride compared with placebo or other non-surgical therapies for the treatment of symptoms of gastro-oesophageal reflux in children. We searched MEDLINE, EMBASE, the Cochrane Controlled Trials Register, Science Citation Index and reference lists for randomized controlled trials which compared cisapride with placebo or other non-surgical therapy in children. We included only trials which reported reflux-related symptoms as an outcome, provided that cisapride was administered orally for at least 1 week. Seven trials (286 children in total) compared cisapride with placebo. Two trials reported good concealment of treatment allocation. The pooled odds ratio for the ,same or worse' symptoms was 0.34 (95%CI 0.10, 1.19). There was substantial heterogeneity between studies (P < 0.00001) and the funnel plot was asymmetrical. Adverse effects (mainly diarrhoea) were not significantly increased with cisapride (pooled odds ratio (OR) 1.80: 0.87, 3.70). The reflux index was significantly reduced in children treated with cisapride (weighted mean difference ,6.49: ,10.13, ,2.85). One study (50 children) compared cisapride with gaviscon plus carobel: the OR for the ,same or worse' symptoms was 3.26 (0.93, 11.38). There was no clear evidence that cisapride reduced symptoms of gastro-oesophageal reflux. As smaller, poorer quality studies were biased in favour of a positive treatment effect, the pooled OR overestimated the potential benefits of cisapride. There was some evidence to suggest that gaviscon plus carobel may be a more effective option than cisapride. [source]

Meta-analysis: the effects of proton pump inhibitors on cardiovascular events and mortality in patients receiving clopidogrel

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 8 2010
C. S. KWOK
Summary Background, Recent studies have suggested an adverse interaction between proton pump inhibitors (PPI) and clopidogrel. Aim, To perform a meta-analysis of cardiovascular outcomes and mortality in patients taking clopidogrel, with and without concomitant PPI. Methods, We searched MEDLINE, EMBASE, Cochrane Controlled Trials Register in October 2009, and checked conference abstracts for randomized and nonrandomized studies that reported the risk of cardiovascular events and mortality with PPI exposure in patients taking clopidogrel. We performed random effects meta-analysis, stratified by study design and assessed heterogeneity using the I2 statistic. Results, Our review included 23 studies covering 93 278 patients. There was substantial heterogeneity in the meta-analyses of major cardiovascular events (19 studies, I2 = 79%) or myocardial infarction (12 studies, I2 = 77%). Analysis of propensity-matched or randomized trial participants showed no associated cardiovascular risk with PPIs, whereas other observational studies generally showed a significant association. Meta-analysis of 13 studies showed no significant association between PPI use and overall mortality (RR 1.09, 95% CI: 0.94,1.26, P = 0.23, I2 = 60%). Conclusion, As there are conflicting and inconsistent data regarding the adverse clopidogrel,PPI interaction, clinicians should focus on potential harm from ulcers/haemorrhage before deciding to omit PPIs in patients taking clopidogrel. [source]

In vitro studies of steroid hormones in neurofibromatosis 1 tumors and schwann cells

MOLECULAR CARCINOGENESIS, Issue 7 2007
Lauren Fishbein
Abstract The most common NF1 feature is the benign neurofibroma, which consists predominantly of Schwann cells. Dermal neurofibromas usually arise during puberty and increase in number throughout adulthood. Plexiform neurofibromas, associated with larger nerves, are often congenital and can be life threatening. Malignant peripheral nerve sheath tumors (MPNST) in NF1 are believed to arise from plexiforms in 5%,10% of patients. There are reports of increased potential for malignant transformation of plexiform tumors and increase in dermal neurofibromas, during pregnancy. These observations suggest that steroid hormones influence neurofibroma growth, and our work is the first to examine steroid hormone receptor expression and ligand-mediated cell growth and survival in normal human Schwann cells and neurofibroma-derived Schwann cell cultures. Immunohistochemistry and real-time PCR showed that estrogen receptors (ERs), progesterone receptor (PR), and androgen receptor are differentially expressed in primary neurofibromas and in NF1 tumor-derived Schwann cell cultures compared to normal Schwann cells. However, there is substantial heterogeneity, with no clear divisions based on tumor type or gender. The in vitro effects of steroid hormone receptor ligands on proliferation and apoptosis of early passage NF1 tumor-derived Schwann cell cultures were compared to normal Schwann cell cultures. Some statistically significant changes in proliferation and apoptosis were found, also showing heterogeneity across groups and ligands. Overall, the changes are consistent with increased cell accumulation. Our data suggest that steroid hormones can directly influence neurofibroma initiation or progression by acting through their cognate receptor, but that these effects may only apply to a subset of tumors, in either gender. © 2007 Wiley-Liss, Inc. [source]

Meta-analysis of digit ratio 2D:4D shows greater sex difference in the right hand

AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 5 2010
Johannes Hönekopp
Objectives: Our aims are, first, to describe the sex difference in the length ratio of the second and fourth digits (2D:4D), which likely reflects prenatal testosterone levels in humans. Second, to infer the loss of reliability observed in 2D:4D based on self-measured finger lengths. Methods: We used random-effects meta-analysis of 2D:4D based on expert-measured finger lengths (116 samples with 13,260 females and 11,789 males). Results: We find a moderate sex difference (with lower 2D:4D for males), which shows substantial heterogeneity (which is unrelated to age). The sex difference is moderated by the type of finger length measurement and by hand. Measurement involving the distortion of soft tissue leads to a significantly larger sex difference than finger length measurement avoiding this. The sex difference in 2D:4D is larger in the right hand than in the left. The reliability of self-measured 2D:4D in the BBC internet study, by far the largest study on 2D:4D, is estimated to be 46% of that of expert-measured 2D:4D. Conclusions: Right-hand 2D:4D might be a better indicator of prenatal androgenisation than left-hand 2D:4D. The view that 2D:4D has allometric properties (Kratochvil L, Flegr J. 2009. Differences in 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line. Biol Lett 5:643,646.) is not supported. Bone lengths contribute to the sex difference in 2D:4D. In addition, there might be a sex difference in fingers' soft tissue, which should be investigated. Because of measurement unreliability, correlations between 2D:4D and variables of interest are about one-third smaller in the BBC internet study than in studies in which 2D:4D is based on expert-measured finger lengths. Am. J. Hum. Biol. 22:619,630, 2010. © 2010 Wiley-Liss, Inc. [source]

The study of organisational autonomy: a conceptual review

PUBLIC ADMINISTRATION & DEVELOPMENT, Issue 2 2004
Koen Verhoest
We argue that contemporary research on the influence of organisational autonomy on performance in public organisations uses a diverse and a too restrictive conceptualisation of autonomy. After discussing that research, the article develops six dimensions of the concept of autonomy in public organisations. Second, weaknesses of contemporary research are shown by confronting their conceptualisations with the developed taxonomy. Third, data from a survey of Flemish public organisations illuminate the need to acknowledge the six different dimensions of autonomy when studying the effect of autonomy on performance. The empirical material points at the dangers of using formal,legal status of a public organisation as an indicator of its autonomy, given substantial heterogeneity of organisations with the same formal,legal status on each dimension of autonomy. Moreover, tensions between different levels of autonomy appear in practice, indicating the need for a combined and integrated study of the effects of the different dimensions of autonomy on performance. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Which clinical factors predict response to prophylactic lithium?

BIPOLAR DISORDERS, Issue 5 2005
A systematic review for bipolar disorders
Objectives:, The aim of this study was to systematically integrate the available evidence on response prediction to prophylactic lithium based on clinical factors. Methods:, Each clinical variable that was related to lithium response in at least one prior study was examined with respect to response prediction. If several studies were located for the same variable, results were integrated using the meta-analytic approach as suggested by DerSimonian and Laird which was developed for substantial heterogeneity in primary studies. Results:, Of 42 potential clinical predictors investigated, five variables were identified as possible response predictors of prophylactic lithium: [1] An episodic pattern of mania-depression-interval, and [2] a high age of illness onset were identified as potentially protective against a recurrence under lithium. [3] A high number of previous hospitalizations, [4] an episodic pattern of depression-mania-interval, and [5] continuous cycling were identified as potential risk factors. Six further variables were found to be significantly related to lithium response, though calculation of fail-safe numbers indicates that current evidence is not sufficient to hold these variables as reliable predictors of lithium response. All effect-sizes relating clinical predictors to response were small to moderate. Conclusions:, Although a few variables are quite robustly supported as response-predictors in this review, a more in-depth analysis of each potential predictor is needed. As none of the potential predictors had a very strong impact on response, prediction of lithium response should be based on a multitude of variables. [source]

A meta-analysis of the association of physical activity with reduced risk of colorectal cancer

COLORECTAL DISEASE, Issue 3 2005
A. K. A. Samad
Abstract Background Physical activity may be associated with reduced risk of colorectal cancer. The main aim of this paper is to review the available evidence for a link between exercise and large bowel cancer. Methods A Cochrane-type methodology was performed. Data extracted included, type of study, type of physical activity measured and the numerical results. The risk ratios (RR) of the studies have been pooled according to the type of study, type of exercise, type of cancer and sex. Pooling was undertaken using fixed effect meta-analysis. A random effect meta-analysis was used where substantial heterogeneity existed. Result Data from 19 cohort studies showed a statistically significant reduction in the risk of colon cancer in physically active males, RR being 0.79 (95% CI 0.72,0.87) and 0.78 (95% CI 0.68,0.91) for occupational and recreational activities, respectively. In women only recreational activities are protective against colon cancer (RR = 0.71, 95%CI 0.57,0.88). Case-control studies showed significantly reduced risks of colon cancer in both sexes irrespective of the type of activity. No protection against rectal cancer is seen in either sex. Conclusion There is considerable evidence that physical activity is associated with reduced risk of colon cancer in both males and females. [source]