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Results for “causality”

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PubMed1993

A statistical causal model for the assessment of dysarthric speech and the utility of computer-based speech recognition.

The evaluation of the degree of speech impairment and the utility of computer recognition of impaired speech are separately and independently performed. Particular attention is paid to the question concerning whether or not there is a relationship between naive listeners' subjective judgements of impaired speech and the performance of a laboratory version of a speech recognition system. It is a difficult task to relate a speech impairment rating with speech recognition accuracy. Towards this end, a statistical causal model is proposed. This model is very appealing in its structure to support inference, and thus can be applied to perform various assessments such as the success of automatic recognition of dysarthric speech. The application of this model is illustrated with a case study of a dysarthric speaker compared against a normal speaker serving as a control.

Adult↗

PubMed1999

Dynamic updating in DIAS-NIDDM and DIAS causal probabilistic networks.

Diabetes advisory system (DIAS) is a decision support system, which has been developed to provide advice on the amount of insulin injected by subjects with insulin-dependent diabetes mellitus (IDDM). DIAS employs a temporal causal probabilistic network (CPN) to implement a stochastic model of carbohydrate metabolism. The CPN network has recently been extended to provide also advice to subjects with noninsulin-dependent diabetes mellitus (NIDDM). However, due to increased complexity and size of the extended CPN the calculations became unfeasible. The CPN network was, therefore, simplified and a novel approach employed to generate conditional probability tables. The principles of dynamic CPN's were adopted and, in combination with the method of conditioning, learning, and forecasting, were implemented in a time- and memory-efficient way. An evaluation using experimental data was carried out to compare the original and revised DIAS implementations employing data collected by patients with IDDM, and to assess the a posteriori identifiability of model parameters in patients with NIDDM.

Adult↗

PubMed2006

Causal influences in the human brain during face discrimination: a short-window directed transfer function approach.

In this letter, we considered the application of parametric spectral analysis, namely a short-window directed transfer function (DTF) approach, to multichannel electroencephalography (EEG) data during a face discrimination task. We identified causal influences between occipitoparietal and centrofrontal electrode sites, the timing of which corresponded to previously reported EEG face-selective components. More importantly we present evidence that there are both feedforward and feedback influences, a finding that is in direct contrast to current computational models of perceptual discrimination and decision making which tend to favor a purely feedforward processing scheme.

Algorithms↗

PubMedDate not supplied

Learning from other people's mistakes: causal understanding in learning to use a tool.

Despite considerable debate about whether nonhuman primates learn to use tools via imitation, this type of learning by children has received surprisingly little attention. The findings of two studies that go some way toward filling this gap are reported here. Study 1 showed that when 2- and 3-year-old children (N = 68) were shown a correct solution to a tool-using task (which they could not solve spontaneously), all the children in both age groups managed at least a partial solution. When children were shown an incorrect solution followed by a correct solution, 2-year-olds again produced only a partial solution. By contrast, most 3-year-olds produced a full solution. Study 2 replicated this age change in a separate sample of children (N = 100) with a different tool-using task. Study 2 also showed that 3-year-olds benefit from observing an incorrect action when it can be contrasted with a correct action: they chose the more effective of the two actions. Taken together, the two studies indicate that by 3 years of age, children do not indiscriminately imitate actions on a tool, but selectively reproduce those actions that have a desired causal effect.

Age Factors↗

PubMed2001

Negative emotions and coronary heart disease: causally related or merely coexistent? A review.

Negative emotions have been claimed to be a cause of coronary heart disease (CHD) as well as a consequence of cardiovascular disorders. Early case studies of cardiac disorders of soldiers in battle drew attention to the possibility that strong negative emotional states could cause CHD. Subsequent reports of reactions to natural disasters supported the notion that intense negative emotions could precipitate somatic disorders such as CHD. Since then, numerous studies have investigated relations between negative emotions and CHD. Over the years, retrospective studies have found, for example, that negative emotions are often present before the occurrence of CHD. Cross-sectional studies have indicated that symptoms of depression and anxiety are often present in CHD patients. Prospective studies have shown that the likelihood of CHD tends to be higher for people with negative emotions than for those without them. The main symptoms of negative emotional states that seem to be most closely associated with CHD are nervousness, getting easily upset, feeling fatigue, being indecisive, having sleep disturbances, being usually worried about something, and feeling that others would be better off if oneself were dead. Although the findings appear to support the notion of causal connections between negative emotions and CHD, they fail to provide conclusive proof of such relations. An alternative explanation that could also account for the findings is simply that negative emotions and CHD often coexist.

Affective Symptoms↗

PubMed2003

Parents' adjustment to late abortion, stillbirth or infant death: the role of causal attributions.

The aim of the present study was to explore the attributional processes and the effect of various causal attributions on post-traumatic symptomatology among 110 parents who had lost an infant. The attributional processes were examined with longitudinal data collected over 12 months. One to four weeks post-loss, approximately half of the parents reported that they were never or rarely concerned with attributing responsibility for their baby's death. The importance of attributing responsibility was associated with several post-traumatic symptoms, as was searching for meaning in the death. Attributions to oneself, others, or God were positively and significantly associated with numerous post-traumatic symptoms. The results are discussed with reference to other studies dealing with the effect of attributions on subsequent adjustment among victims of trauma.

Abortion, Spontaneous↗

PubMed2001

Pregnancy smoking and childhood conduct problems: a causal association?

Recent investigations have highlighted associations between maternal smoking in pregnancy and antisocial behaviour in offspring, and suggested the possibility of a causal effect. We used data from the 1970 British birth cohort study (BCS70) to examine these links in a large. population-based sample studied prospectively from birth to age 16. We found a strong dose-response relationship between the extent of pregnancy smoking and childhood-onset conduct problems, but no links with adolescent-onset antisocial behaviours. Effects on childhood-onset conduct problems were as marked for girls as for boys, and were robust to controls for a variety of social background factors and maternal characteristics. Controls for mothers' subsequent smoking history modified this picture, however, suggesting that the prime risks for early-onset conduct problems may be associated with persistent maternal smoking--or correlates of persistent smoking--rather than with pregnancy smoking per se.

Adolescent↗

PubMed2001

Utilizing propensity scores to estimate causal treatment effects with censored time-lagged data.

Observational studies frequently are conducted to compare long-term effects of treatments. Without randomization, patients receiving one treatment are not guaranteed to be prognostically comparable to those receiving another treatment. Furthermore, the response of interest may be right-censored because of incomplete follow-up. Statistical methods that do not account for censoring and confounding may lead to biased estimates. This article presents a method for estimating treatment effects in nonrandomized studies with right-censored responses. We review the assumptions required to estimate average causal effects and derive an estimator for comparing two treatments by applying inverse weights to the complete cases. The weights are determined according to the estimated probability of receiving treatment conditional on covariates and the estimated treatment-specific censoring distribution. By utilizing martingale representations, the estimator is shown to be asymptotically normal and an estimator for the asymptotic variance is derived. Simulation results are presented to evaluate the properties of the estimator. These methods are applied to an observational data set of acute coronary syndrome patients from Duke University Medical Center to estimate the effect of a treatment strategy on the mean 5-year medical cost.

Analysis of Variance↗

PubMed2004

An extended general location model for causal inferences from data subject to noncompliance and missing values.

Noncompliance is a common problem in experiments involving randomized assignment of treatments, and standard analyses based on intention-to-treat or treatment received have limitations. An attractive alternative is to estimate the Complier-Average Causal Effect (CACE), which is the average treatment effect for the subpopulation of subjects who would comply under either treatment (Angrist, Imbens, and Rubin, 1996, Journal of American Statistical Association 91, 444-472). We propose an extended general location model to estimate the CACE from data with noncompliance and missing data in the outcome and in baseline covariates. Models for both continuous and categorical outcomes and ignorable and latent ignorable (Frangakis and Rubin, 1999, Biometrika 86, 365-379) missing-data mechanisms are developed. Inferences for the models are based on the EM algorithm and Bayesian MCMC methods. We present results from simulations that investigate sensitivity to model assumptions and the influence of missing-data mechanism. We also apply the method to the data from a job search intervention for unemployed workers.

Algorithms↗

PubMed2006

Marijuana use and depression among adults: Testing for causal associations.

AIM: To determine whether marijuana use predicts later development of depression after accounting for differences between users and non-users of marijuana. DESIGN: An ongoing longitudinal survey of 12 686 men and women beginning in 1979. SETTING: The National Longitudinal Survey of Youth of 1979, a nationally representative sample from the United States. PARTICIPANTS: A total of 8759 adults (age range 29-37 years) interviewed in 1994 had complete data on past-year marijuana use and current depression. MEASUREMENTS: Self-reported past-year marijuana use was tested as an independent predictor of later adult depression using the Center for Epidemiologic Studies-Depression questionnaire. Individual's propensity to use marijuana was calculated using over 50 baseline covariates. FINDINGS: Before adjusting for group differences, the odds of current depression among past-year marijuana users is 1.4 times higher (95% CI: 1.1, 1.9) than the odds of depression among the non-using comparison group. After adjustment, the odds of current depression among past-year marijuana users is only 1.1 times higher than the comparison group (95% CI: 0.8, 1.7). Similarly, adjustment eliminates significant associations between marijuana use and depression in four additional analyses: heavy marijuana use as the risk factor, stratifying by either gender or age, and using a 4-year lag-time between marijuana use and depression. CONCLUSIONS: After adjusting for differences in baseline risk factors of marijuana use and depression, past-year marijuana use does not significantly predict later development of depression. These findings are discussed in terms of their relevance for understanding possible causal effects of marijuana use on depression.

Adult↗

PubMed1980

Meat wrapper's asthma: identification of the causal agent.

Meat wrapper's asthma is a typical example of occupational asthma due to emissions from chemical products. The authors report three new cases due to the use of the now classic meat packaging techniques in supermarkets. The chemical agents involved were identified. Inhalation tests have been carried out in one patient with the complete wrappings, i.e. the PVC film and the price labels, and separate tests were performed with eight additives of the PVC film, and with phthalic anhydride and di-cyclohexylphthalate emitted from heated price labels. These tests incriminate two products: phthalic anhydride seems to be the principal causal agent and epoxidized soybean oil can be suspected as a secondary agent causing this occupational asthma.

Adult↗

PubMed2006

Biodiversity as both a cause and consequence of resource availability: a study of reciprocal causality in a predator-prey system.

1. One of the oldest questions in ecology is how species diversity in any given trophic level is related to the availability of essential resources that limit biomass (e.g. water, nutrients, light or prey). Researchers have tried to understand this relationship by focusing either on how diversity is influenced by the availability of resources, or alternatively, how resource abundance is influenced by species diversity. These contrasting perspectives have led to a seeming paradox '... is species diversity the cause or the consequence of resources that limit community biomass?' 2. Here we present results of an experiment that show it is possible for species diversity and resource density to exhibit reciprocal causal relationships in the same ecological system. Using a guild of ladybeetle predators and their aphid prey, we manipulated the number of predator species in field enclosures to examine how predator diversity impacts prey population size. At the same time, we manipulated the abundance of aphid prey in discrete habitat patches within each enclosure to determine how smaller-scale spatial variation in resource abundance affects the number of co-occurring predator species. 3. We found that the number of ladybeetle species added to enclosures had a significant impact on aphid population dynamics because interference competition among the predators reduced per capita rates of predation and, in turn, the overall efficiency of the predator guild. At the same time, spatial variation in aphid abundance among smaller habitat patches generated variation in the observed richness of ladybeetles because more species occurred in patches where predators aggregated in response to high aphid density. 4. The results of our experiment demonstrate that it is possible for species diversity to simultaneously be a cause and a consequence of resource density in the same ecological system, and they shed light on how this might occur for groups of mobile consumers that exhibit rapid responses to spatial and temporal variation in their prey.

Animals↗

PubMed2006

A review of causal factors and control measures for bloat in farmed salmonids with a suggested mechanism for the development of the condition.

A mechanism for the development of bloat in salmonids is proposed and explained in terms of the physiology of digestion and osmoregulation in fish. Understanding the causal factors for bloat enables control measures to be identified. In farmed salmonids, the chyme produced during the digestion of nutrient-rich pelleted foods that rapidly disintegrate in the stomach will be a potent activator of a negative feedback mechanism (enterogastric control), which slows stomach emptying to protect the small intestine from nutrient overload. In saline environments salmonids continuously drink sea water to replace fluid lost across the gills. Fluid loss is increased during periods of stress caused by factors such as low oxygen levels, elevated temperature or high salinity. When ingestion of nutrient-rich food results in prolonged activation of enterogastric control, slowed stomach emptying leads to decreased absorption of water, thirst and increased drinking. This further exacerbates stomach distention. The proposed mechanism for the development of bloat is supported by on-farm experience where measures to control bloat include reducing food intake, altering the composition of the diet and using appropriate strategies to reduce stress.

Air Sacs↗

PubMed1993

When can cerebral palsy be prevented? The generation of causal hypotheses by multivariate analysis of a case-control study.

Causal hypotheses for spastic cerebral palsy were sought by comparing a population based sample of 183 cases with 549 matched controls. A time-ordered multivariate analysis was used to distinguish confounders and consequences of disease from possible causes, which could be single factors or sequences of factors. Eighteen factors were identified as having an association with spasticity that did not arise by confounding with other identified factors nor as a consequence of the disease. Nearly half the cases (48.6%) but only 14.4% of controls experienced one or more of these factors, but no one factor was experienced by > 11%, and most by < 5%, of cases. Those factors identified as occurring before labour commenced affected 35% of all cases. The proportion of cases experiencing identified factors and the distribution of those factors between epochs varied with gestation of delivery and with description and severity of impairment. The possible timing of causes in cases without identified factors and the role of preterm birth and poor intrauterine growth are discussed. We conclude that there were many pathways to spastic cerebral palsy many of which could not be identified. Each contributed only a small proportion and many may have been multifactorial. Intrapartum initiation of the aetiological pathway was relatively unimportant, being likely in about 9% of cases, but the majority of pathways commenced predelivery.

Adult↗

PubMed1992

Further evidence supporting a causal relationship between prone sleeping position and SIDS.

A 3 year case-control study identifying the risk factors for SIDS was undertaken. Preliminary analysis of the data from the first year suggested that SIDS mortality could fall by 50% if the prevalence of the prone sleeping position changed from 40 to 0%. During the 3 year study the prevalence of the prone sleeping position among infants has fallen from 43% in the first year to 20% in the third year. SIDS mortality has fallen to 3.1/1000 live births, which is very close to that predicted. When considered with other available evidence this strongly supports a causal relationship between the prone sleeping position and SIDS.

Case-Control Studies↗

PubMed1997

Causality of parenchymal and vascular changes in rats with experimental thiamine deficiency encephalopathy.

The causality of vascular and parenchymal damage to the central nervous system (CNS) was examined in rats with thiamine deficiency. Male Sprague-Dawley rats were divided into two groups; one was given a thiamine-deficient diet (TDD) and injected intraperitoneally with 10 micrograms/100 g bodyweight pyrithiamine (PT) in order to analyze morphometrically the topographical and sequential relationship between vascular and parenchymal changes and vasodilatation, and the other was given a TDD and 50 micrograms/100 g bodyweight PT in order to determine hemorrhagic sites using serial sections. Histological examination showed that spongiotic change occurred selectively in the inferior colliculus (100%) from day 19, and thereafter in the thalamus (95%), mammillary body (50%) and nuclei olivaris and vestibularis of the pons (25%), with or without hemorrhage. Simultaneously, glycogen accumulation was also observed in these regions at a frequency similar to that of hemorrhage. Ultrastructurally, however, hydropic swelling of astrocytic and neuronal processes without glycogen accumulation was observed as early as day 9 in the inferior colliculus, at which time an increase of glial fibrillary acidic protein-positive processes was also recognized. The superior colliculus was completely spared. From day 22 vasodilatation of the inferior colliculus occurred, concomitantly with bodyweight loss and neurological symptoms. Twenty-two examined hemorrhages, which occurred in the thalamus and inferior colliculus, were distributed along the arterioles or capillaries on the arterial side. In conclusion, the morphological CNS changes caused by thiamine deficiency with administration of low-dose PT in rats begin as hydropic swelling of neuronal and astrocytic processes, followed by hemorrhage and, thereafter, by vasodilation. The predilection for hemorrhage on the arterial side without parenchymal changes suggests that petechial hemorrhage is not simply secondary to parenchymal changes, but is due to hemodynamic change resulting from thiamine deficiency-induced vascular dysfunction.

Animals↗

PubMed1990

Familial hypocalciuric hypercalcaemia and pancreatitis: no causal link proven.

A case of a patient with pancreatitis and familial hypocalciuric hypercalcaemia is presented and the literature linking FHH and pancreatitis is reviewed. The case for a causal link between the two conditions is not proven and seems unlikely. In view of this we strongly challenge the recommendation of total parathyroidectomy in such cases.

Adult↗

PubMed1994

Scleroderma and augmentation mammoplasty--a causal relationship?

BACKGROUND: The studies implicating a causal relationship between silicone and scleroderma, other autoimmune disease, and fibromyalgia-like symptoms have been largely descriptive with absence of appropriate controls and no consideration of potential confounders. This case control study of augmentation mammoplasty and scleroderma represents an attempt to answer these deficiencies. AIMS: To compare the frequency and temporal relationship of augmentation mammoplasty in interviewed and deceased cases and interviewed controls. To determine the frequencies of exposure to non-augmentation mammoplasty silicone, and to determine the frequencies of mastectomy and breast lumpectomy in interviewed cases and controls. METHODS: Scleroderma cases and age-stratified general practice controls were interviewed using a prepilotted telephone questionnaire. Self-reported date/s of augmentation mammoplasty were ascertained, as were dates of onset of first and second scleroderma symptom/s and scleroderma diagnosis, where relevant. Comparison of socioeconomically adjusted rates was expressed in terms of rate ratios. RESULTS: Augmentation mammoplasty rates were comparable between interviewed cases and controls. No augmentation mammoplasty procedures were documented in deceased scleroderma patients' medical records. Rates of exposure to non-mammoplasty silicone, mastectomy and breast lumpectomy were comparable in interviewed cases and controls. CONCLUSIONS: This study failed to demonstrate an association between silicone breast implantation and the subsequent development of scleroderma, to a relative risk level as low as 4.5 with 90% power.

Adult↗