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Results for “Explainability”

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At least 181 records · Page 10Linked to original sources

PubMed1998

A comparative study of iatrogenesis, medication abuse, and psychiatric morbidity in chronic pain patients with and without medically explained symptoms.

We report a case control study comparing patients attending a pain clinic whose symptoms were not considered medically explained (cases) with those whose symptoms were considered medically explained (controls). Principal comparisons were psychiatric morbidity, medication use, and iatrogenic factors assessed by interview, and questionnaire measures of anxiety, depression, functional impairment, coping strategies and pain beliefs. Medically unexplained symptoms were associated with the presence of psychiatric morbidity (odds ratio = 3.4, 95% C.I.: 1.4,8.2), and of possible iatrogenic factors. There were no significant differences with regards to medication abuse/dependence.

Adult↗

PubMed2002

Can mutation or fixation biases explain the allele frequency distribution of human single nucleotide polymorphisms (SNPs)?

One of the most abiding controversies in evolutionary biology concerns the role of neutral processes in molecular evolution. A main focus of the debate has been the evolution of isochores, the strong and systematic variation of base composition in mammalian genomes. One set of hypotheses argue that regions of similar GC are owing to localised mutational biases coupled with neutral evolution. The alternatives point to either selection or biased gene conversion as mechanisms to preferentially remove A or T bases, favouring G and C instead. Using a novel method, we compare models including such fixation biases to models based on mutation bias alone, under the assumption that non-coding, non-repetitive human DNA is at compositional equilibrium. While failing to fully explain the allele frequency distributions of recent single nucleotide polymorphism data, we show that the data are best fitted if the mutation bias is assumed to be constant across the genome, while fixation bias varies with GC content. We also attempt to estimate the strength of fixation bias, which increases linearly with increasing GC. Our approximation suggests that this force exists within the necessary parameter range: it is not so weak as to be drowned by random drift, but not so strong as to lead to exclusive use of G and C alone. Together these results demonstrate that mutation bias fails to explain the evolution of isochores, and suggest that either selection or biased gene conversion are involved.

Alleles↗

PubMed2000

Greater late lumen loss after successful coronary balloon angioplasty in the proximal left anterior descending coronary artery is not explained by extent of vessel wall damage or plaque burden.

OBJECTIVES: We investigated whether the greater late lumen loss after coronary balloon angioplasty in the proximal left anterior descending artery (P-LAD) compared with that in other segments might be related to differences in vascular dimensions or morphology as determined by angiography and intravascular ultrasound imaging. BACKGROUND: The greater late lumen loss after angioplasty in the P-LAD that has been observed in several studies has not been explained. METHODS: We studied 178 patients and 194 coronary artery lesions by quantitative angiography and 30 MHz intravascular ultrasound imaging after successful balloon angioplasty. Vessel wall morphology was compared among three proximal and three nonproximal segments. Follow-up quantitative angiography for late lumen loss calculation was performed in 168 lesions. Multivariate analysis was used to determine predictors of late lumen loss. RESULTS: Absolute and relative late loss were significantly greater at the P-LAD compared with the pooled group of other segments (0.42 +/- 0.60 mm vs. 0.10 +/- 0.48 mm, p = 0.0008 and 0.14 +/- 0.24 vs. 0.03 +/- 0.17, p < 0.001). Also, a greater percentage of calcific lesions (65% vs. 44%, p = 0.034), a lower incidence of rupture (51% vs. 74%, p = 0.009) and a larger reference segment plaque area (5.4 +/- 2.2 mm2 vs. 4.7 +/- 1.9 mm2, p = 0.05) were found in the P-LAD. In multivariate analysis however, these variables were not predictive of late loss. CONCLUSIONS: Greater late lumen loss after coronary balloon angioplasty of the P-LAD is not explained by differences in atherosclerotic plaque burden or in vessel wall damage.

Aortic Dissection↗

PubMed2002

Can cardiovascular risk factors explain the association between education and cardiovascular disease in young women?

We sought to explain the observed variation in the relationship between education and cardiovascular disease (CVD) among young women in countries at different stages of economic development. Data comprised 2,478 cases of acute myocardial infarction (AMI) or stroke and 6,819 age-matched controls from Africa, Asia, Eastern Europe, and Latin America. The risks of AMI associated with lower education observed in Eastern Europe and higher education in non-European countries were reduced by 92% in Eastern Europe and totally abolished in non-European countries by adjustment for standard cardiovascular risk factors. The inverse associations between education and stroke risk in the three non-African regions were attenuated by 22, 47, and 60% after adjustment. In Africa, the slight inconsistent trend towards lower stroke risk in less well educated women was unaffected by adjustment. These data suggest that standard risk factors explain a substantial proportion if not all of the difference in AMI risk associated with education but a lesser proportion of educationally linked stroke risk.

Adult↗

PubMed2000

Cooperative equilibrium transitions coupled with a slow annealing step explain the sharpness and hysteresis of collagen folding.

Heat and guanidinium-induced denaturation curves of collagen III and its fragments were fitted by theoretical models to explain the extreme sharpness and the hysteresis between unfolding and refolding. It was shown that a recently proposed kinetic model for collagen denaturation does not account for the observed steepness, with physically reasonable values of activation energy and frequency factors in the Arrhenius equation. The extreme slope, which amounts to 0.38 per centigrade for collagen III at the midpoint of its transition, can only be explained by a highly cooperative equilibrium model. The refolding curve is shifted to lower temperatures by 6 degrees C for collagen III and reversible unfolding matching the initial profile of the native protein is observed only after long-time annealing. A simple formalism is proposed by which experimental denaturation and refolding curves are quantitatively described. The transition proceeds via many cooperative steps with slightly different equilibrium constants for unfolding and refolding. Hysteresis and annealing are caused by very slow steps, which are probably connected with a rearrangement of misfolded regions. These slow steps disappear with decreasing size of collagen fragments and hysteresis is not found for collagen model peptides.

Animals↗

PubMed2003

Can patient-, treatment- and pathology-related characteristics explain the high local recurrence rate following breast-conserving therapy in young patients?

The aim of this study was to identify patient-, tumour- or treatment-related factors associated with young age that might explain the higher risk of ipsilateral breast recurrence that occurs after breast-conserving therapy (BCT) in young breast cancer patients. In the 'boost versus no boost trial', 5569 early-stage breast cancer patients were entered. All patients underwent tumorectomy followed by whole breast irradiation of 50 Gy. Patients having a microscopically complete excision were randomised between receiving no boost or a 16-Gy boost, while patients with a microscopically incomplete excision were randomised between receiving a boost dose of 10 or 26 Gy. The 5-year local control rate was 82% for patients 60 years of age (P<0.0001). In young patients, the tumour was significantly larger and more often oestrogen and progesterone receptor-negative. Invasive carcinoma and the intraductal component were more often of a high grade. The intraductal component was more frequently incompletely resected in young patients. Re-excisions were performed more often (most probably due to a more frequent incomplete excision at the first attempt). The total volume of breast tissue removed at the tumorectomy was smaller in the younger patient group, even after including the volume removed during re-excision. When relating all these parameters (including age itself) to local control, the multivariate analysis stratified by treatment showed that age was the only independent prognostic factor for local control (P=0.0001). Including the boost treatment as a separate covariate, the analysis retained age and boost treatment as significant factors related to local control (P<0.0001). It was shown that the boost dose significantly reduced the 5-year local recurrence rate from 7 to 4% for patients with a complete excision (P<0.001). For patients 40 years of age or younger, the boost dose reduced the local recurrence rate from 20 to 10% (P=0.002). This large European Orgnaization for Research and Treatment of Cancer (EORTC) trial demonstrated an increased local recurrence rate in young patients. Although several associations between patient, tumour and treatment factors and age were found, that might explain the high local recurrence rate in the younger patients, it appears that age itself and the boost dose were the only factors that were independently related to local control.

Adult↗

PubMed1996

Short strong hydrogen bonds: can they explain enzymic catalysis?

It has been proposed that some remarkable enzymic catalytic effects can be explained by the existence of unusually strong hydrogen bonds within the enzyme's active site. Although such hydrogen bonds may be short, and may have unusual properties, there is no evidence that unusually strong hydrogen bonds exist in solution or in enzyme active sites. Thus there is no basis for invoking strong hydrogen bonds to explain enzymic rate enhancements.

Catalysis↗

PubMed2002

Does low birth weight help to explain the increased prevalence of asthma among African-Americans?

BACKGROUND: Racial disparities in asthma prevalence are not fully explained. Previous studies have reported an association between low birth weight (LBW) and asthma. African-Americans are at a heightened risk for both conditions. OBJECTIVE: The objective of this analysis was to study a sample of suburban schoolchildren to determine if increased asthma prevalence in African-Americans could be explained by report of LBW. METHODS: Logistic regression was used to analyze telephone survey and clinical data for a sample of 126 children, aged 6 to 8 years. RESULTS: African-Americans reported asthma (12.5% vs 5.3%) and LBW (16.6% vs 3.9%) more frequently than non-African-Americans. After adjusting for LBW, the odds ratio for the association of African-American race to asthma was reduced from 2.6 to 1.8, whereas LBW remained independently associated with asthma, adjusted odds ratio = 5.1 (95% CI:1.4 to 18.9). The adjusted population risk for asthma due to LBW was 0.31. CONCLUSIONS: High rates of LBW for African-Americans may contribute to racial disparities in asthma prevalence.

Asthma↗

PubMed1998

Untreated growth hormone deficiency explains premature mortality in patients with hypopituitarism.

Untreated growth hormone deficiency (GHD) might explain the increased mortality reported in patients with hypopituitarism. These statistics appear to be largely attributable to cardiovascular disease. Differences in fibrinolytic activity regulators, together with dyslipidaemias, abdominal obesity and raised blood pressure in hypopituitarism might explain this increased risk. There is growing evidence that treatment with growth hormone (GH) can rectify most of the cardiovascular abnormalities associated with GHD. The reported improved psychosocial well-being in response to GH treatment may also be important in lowering risk in this group of patients.

Cardiovascular Diseases↗

PubMed1999

Can biased symptom perception explain false-alarm choking sensations?

BACKGROUND: Breathlessness in asthma often cannot be explained with objective variables indicating airways obstruction. The hypothesis that unrealistic breathlessness results from false interpretation of sensations was tested. METHODS: Sixty-four children and adolescents with asthma, aged 9-18 years, were randomly assigned to; (1) standardized physical exercise for induction of general symptoms; (2) equipment causing itching through skin irritation; or (3) physical exercise combined with equipment causing itching through skin irritation. Pre-test and post-test measures were: lung function; breathlessness; general symptoms; itching; state anxiety; and worry. RESULTS: Lung function decreased within normal parameters (3.8%, 1.1%, 2.6%, respectively) and did not differ significantly between conditions. Breathlessness increased significantly after exercise, particularly in condition 3. Breathlessness correlated with general symptoms and worrying, but not with changes in lung function, age, or asthma severity. CONCLUSION: Biased symptom perception can explain unrealistic breathlessness. Prerequisites are situational cues triggering selective perception and ambiguous sensations associated with the anticipated (feared) physical state. Excessive breathlessness may often warrant objective confirmation by means of lung-function testing.

Adolescent↗

PubMed2000

Schizophrenia among Surinamese in the Netherlands: high admission rates not explained by high emigration rates.

BACKGROUND: A high risk of schizophrenia has been found among Caribbean immigrants in the Netherlands and Great Britain. One hypothesis to explain these findings is that patients with a diagnosis of schizophrenia or patients with symptoms of psychosis not specifically diagnosed, emigrate more than the general population. Such selection might account for high rates of Surinamese patients with a diagnosis of schizophrenia in Netherlands psychiatric hospitals. We examined this hypothesis. METHODS: The files of patients with schizophrenia or patients suffering from unspecified psychosis were selected from the archives of the National Psychiatric Hospital in Surinam. These patients were traced to investigate patterns of emigration. Data from the Central Bureau for Statistics in the Netherlands and from the Central Population Bureau in Surinam provided the percentage of the general Surinamese population that emigrated to the Netherlands. The difference between the two percentages was evaluated using the chi-squared test. Using the same method the percentage of remigration from the Netherlands among Surinamese patients was compared with the percentage of remigration among the general Surinamese population. RESULTS: Surinamese patients with schizophrenia or unspecified psychosis did not emigrate more frequently to the Netherlands compared with the general Surinamese population. They did remigrate significantly more frequently. CONCLUSION: High migration rates do not explain the high hospital admission rates for schizophrenia among Surinamese in the Netherlands.

Adolescent↗

PubMed2001

A homeostatic model of oxidative damage explains paradoxes observed in earlier aging experiments: a fusion and extension of older theories of aging.

The Rate of Living and the Threshold Theories of Aging are two contradicting approaches used to explain experimental facts about aging in fruit flies. In this paper we suggest an approach that unifies these theories and removes the contradiction. The approach involves quantitative description of the oxidative stress theory of aging, which is presented in the form of a mathematical homeostatic model. The crucial variable in the model is called 'homeostatic capacity', which is analogous to the classical notion of vitality. We model the process of aging as the age-related accumulation of damage produced by oxidative stress, which reduces the homeostatic capacity of the organism. The model is tested with the experimental data obtained in the classical experiments by Maynard Smith in 1958-1963. Our homeostatic model explains the well-known results of these experiments more accurate than any one of the early theories of aging. We form an hypothesis about the mechanisms underlying the results observed in the experiments and analyze a possible interplay of these mechanisms. Our virtual replication of Maynard Smith's classical experiments demonstrates that mathematical modeling can be a powerful tool to reveal and investigate the inherent genetic and physiological processes underlying the data observed in complicated insect experiments.

Aging↗

PubMed1997

Explained and unexplained medical symptoms in generalized anxiety and panic disorder: relationship to the somatoform disorders.

We have examined the numbers and types of symptoms in a sample of 90 patients with generalized anxiety disorder (GAD) and 77 patients with panic disorder (PD) collected from six different sites during the conduct of a multicenter clinical trial. This information was obtained utilizing the Health Questionnaire, a 47-item self-report list of medical symptoms, patterned after the Somatization Disorder section of the Diagnostic Interview Schedule. Although the patients in this sample had a wide variety of medically explained and unexplained physical symptoms, none of them qualified for a diagnosis of somatization disorder by DSM-III-R criteria. GAD and PD patients reported remarkably similar numbers of explained and unexplained medical symptoms. The panoply of somatic symptoms presented by these patients presents a formidable diagnostic challenge for clinicians. These findings suggest that the pattern of overutilization of medical services that is well documented for PD patients may also be found for GAD patients.

Adult↗

PubMed1992

General slowing alone cannot explain age-related search effects: reply to Cerella (1991)

Cerella (1991) has argued that the performance of older adults in the Fisk and Rogers (1991) study is a linear function of the performance of younger adults that is independent of task-specific cognitive requirements. We demonstrate that this is not the case. First, we show that the scatter plot analyses used by Cerella can hide the very task-specific age-related slowing they were designed to reveal. Second, we demonstrate that the percentage of variance explained by such analyses can be misleading. Third, we show that there are reliable differences across tasks in the parameters relating younger and older adults' performance. Finally, we argue that the general, task-independent proportionate slowing that Cerella suggested explains so much of the variance in age-related performance is actually an average slowing that is a function of a relatively small task-independent and a relatively large task-dependent factor.

Adult↗

PubMed1996

Usefulness of the protection motivation theory in explaining hearing protection device use among male industrial workers.

The present study examined the usefulness of personal variables: noise annoyance, and components of the protection motivation theory (R. W. Rogers, 1983) along with social-organizational factors in explaining hearing protection device (HPD) use among Israeli manufacturing workers. Participants were 281 men exposed to harmful noise levels for which routine HPD use is required by regulation. In practice, 3 HPD user groups were identified: nonusers (n = 38), occasional users (n = 125), and regular users (n = 118). HPD use was objectively verified. HPD use was primarily related to the personal variables but not to management pressure, coworker pressure, or family support. The most powerful predictors of HPD use were perceived self-efficacy (for long-term HPD use), perceived susceptibility (to hearing loss), and noise annoyance, together explaining 48% of the outcome variance. These findings have implications for interventions aimed at motivating workers to use HPDs regularly.

Adolescent↗

PubMed2000

On measures of explained variance in nonrecursive structural equation models.

Whereas measures of explained variance in a regression and an equation of a recursive structural equation model can be simply summarized by a standard R2 measure, this is not possible in nonrecursive models in which there are reciprocal interdependencies among variables. This article provides a general approach to defining variance explained in latent dependent variables of nonrecursive linear structural equation models. A new method of its estimation, easily implemented in EQS or LISREL and available in EQS 6, is described and illustrated.

Analysis of Variance↗

PubMed2001

Explaining employees' health care costs: a prospective examination of stressful job demands, personal control, and physiological reactivity.

The authors tested the ability of stressful demands and personal control in the workplace to predict employees' subsequent health care costs in a sample of 105 full-time nurses. Both subjective and objective measures of workload demands interacted with personal control perceptions in predicting the cumulative health care costs over the ensuing 5-year period. Tonic elevations in salivary cortisol, moreover, mediated the effects of demands and control on health care costs. Neither the job demands variables nor physiological reactivity measures, however, explained subsequent mental health. The results support findings from the epidemiological literature that demonstrate an important role for employees' control in explaining occupational inequalities in coronary heart disease and mortality. The authors argue that the results also encourage control-enhancing job design interventions by suggesting that their outcomes can benefit both organizations and their members.

Adult↗

PubMed2002

Does a prosocial-selfish distinction help explain the biological affects? Comment on Buck (1999).

R. Buck (1999) argued that a conceptual distinction between prosocial and selfish motivation is necessary to understand the biological affects (consciously experienced feelings and desires having an innate neurochemical basis). However, at a biological level of analysis, a prosocial-selfish distinction is doubtful empirically and conceptually. For this reason, Buck's proposed typology of biological affects is unclear. Moreover, a prosocial-selfish distinction is not necessary to explain hemispheric differences in brain activity associated with affect. In contrast, an approach-withdrawal distinction explains some data uniquely well, although numerous exceptions imply that simple models are inadequate. To extend hemispheric models of experienced emotion, a prosocial-selfish distinction is unlikely to be explanatory, whereas an alternative account based on a distinction between verbal and nonverbal working memory may be useful.

Affect↗