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Results for “causality”

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PubMed2002

Causal knowledge as a prerequisite for confounding evaluation: an application to birth defects epidemiology.

Common strategies to decide whether a variable is a confounder that should be adjusted for in the analysis rely mostly on statistical criteria. The authors present findings from the Slone Epidemiology Unit Birth Defects Study, 1992-1997, a case-control study on folic acid supplementation and risk of neural tube defects. When statistical strategies for confounding evaluation are used, the adjusted odds ratio is 0.80 (95% confidence interval: 0.62, 1.21). However, the consideration of a priori causal knowledge suggests that the crude odds ratio of 0.65 (95% confidence interval: 0.46, 0.94) should be used because the adjusted odds ratio is invalid. Causal diagrams are used to encode qualitative a priori subject matter knowledge.

Bias↗

PubMed2001

Iron deficiency and reduced work capacity: a critical review of the research to determine a causal relationship.

The causal relationship between iron deficiency and physical work capacity is evaluated through a systematic review of the research literature, including animal and human studies. Iron deficiency was examined along a continuum from severe iron-deficiency anemia (SIDA) to moderate iron-deficiency anemia (MIDA) to iron deficiency without anemia (IDNA). Work capacity was assessed by aerobic capacity, endurance, energetic efficiency, voluntary activity and work productivity. The 29 research reports examined demonstrated a strong causal effect of SIDA and MIDA on aerobic capacity in animals and humans. The presumed mechanism for this effect is the reduced oxygen transport associated with anemia; tissue iron deficiency may also play a role through reduced cellular oxidative capacity. Endurance capacity was also compromised in SIDA and MIDA, but the strong mediating effects of poor cellular oxidative capacity observed in animals have not been demonstrated in humans. Energetic efficiency was affected at all levels of iron deficiency in humans, in the laboratory and the field. The reduced work productivity observed in field studies is likely due to anemia and reduced oxygen transport. The social and economic consequences of iron-deficiency anemia (IDA) and IDNA have yet to be elucidated. The biological mechanisms for the effect of IDA on work capacity are sufficiently strong to justify interventions to improve iron status as a means of enhancing human capital. This may also extend to the segment of the population experiencing IDNA in whom the effects on work capacity may be more subtle, but the number of individuals thus affected may be considerably more than those experiencing IDA.

Algorithms↗

PubMed1990

Randomization, statistics, and causal inference.

This paper reviews the role of statistics in causal inference. Special attention is given to the need for randomization to justify causal inferences from conventional statistics, and the need for random sampling to justify descriptive inferences. In most epidemiologic studies, randomization and random sampling play little or no role in the assembly of study cohorts. I therefore conclude that probabilistic interpretations of conventional statistics are rarely justified, and that such interpretations may encourage misinterpretation of nonrandomized studies. Possible remedies for this problem include deemphasizing inferential statistics in favor of data descriptors, and adopting statistical techniques based on more realistic probability models than those in common use.

Bayes Theorem↗

PubMed2000

Causal influences in primate cerebral cortex during visual pattern discrimination.

Anatomical studies of the visual cortex demonstrate the existence of feedforward, feedback and lateral pathways among multiple cortical areas. Yet relatively little evidence has previously been available to show the causal influences of these areas on one another during visual information processing. We simultaneously recorded event-related local field potentials (LFPs) from surface-to-depth bipolar electrodes at six sites in the ventral region of the right hemisphere visual cortex in a highly trained macaque monkey during performance of a visual pattern discrimination task. Applying a new statistical measure, the short-time directed transfer function (STDTF), to the LFP data set, we charted the changing strength and direction of causal influence between these cortical sites on a fraction-of-a-second time scale. We present results showing, for the first time, the dynamics of distinct feedforward, feedback and lateral influences in the ventral portion of the primate visual cortex during visual pattern processing.

Action Potentials↗

PubMed1996

Causal attributions, coping strategies, and adjustment to breast cancer.

In this retrospective questionnaire study of a convenience sample of 244 Australian women, type of causal attributions and their impact on coping strategies adopted by women with breast cancer were studied in relation to women's adjustment to their illness. Although 70% of the women made attributions about their cancer's origins, these women were not significantly better adjusted than women who had not make an attribution. Of those women who had made a causal attribution, type of attribution, whether controllable or uncontrollable (based on perceptions as to the controllability/uncontrollability of the cause of the disease), determined the extent to which exhibited information-seeking behavior. In the present study, women who perceived the cause of their cancer as emanating from uncontrollable circumstances were more active in seeking information about breast cancer than women who perceived the cause of their cancer as emanating from controllable circumstances. Different types of coping strategies adopted by women were associated with adjustment. Women who rated their adjustment as excellent displayed lower levels of helplessness, made fewer changes to their social behavior, were more anxiously preoccupied with their illness, sought more alternatives to medical therapy, and exhibited more information-seeking behavior than did their less-well-adjusted counterparts. The theoretical and practical implications of these results are discussed.

Adaptation, Psychological↗

PubMed1993

A causal model of health status and satisfaction with medical care.

Patients with better health status have often been shown to be more satisfied with their medical care, but the causal factors in this relation have not been determined. In this study, a longitudinal assessment of these two constructs was undertaken in which older patients in a health maintenance organization were interviewed at baseline (N = 590) and again 1 year later (N = 526) about their health status and satisfaction with their medical care. Structural equation modeling using LISREL procedures revealed that the predominant direction of causation went from earlier self-perceived overall health and functional ability to later levels of satisfaction. There was no evidence for causal paths going from satisfaction to later health. In addition, a test of spuriousness indicated that for self-perceived overall health, the significant longitudinal path was unlikely to be explained by unmeasured confounding variables.

Activities of Daily Living↗

PubMedDate not supplied

The causal role for genital ulcer disease as a risk factor for transmission of human immunodeficiency virus. An application of the Bradford Hill criteria.

BACKGROUND AND OBJECTIVES: Genital ulcer disease (GUD) has been reported to increase the risk for the acquisition of human immunodeficiency virus (HIV). Although many investigators have reported an increased risk for HIV infection in persons with concurrent or previous GUD, not all studies have been designed to determine whether GUD causes an increased risk for HIV infection or acts only as a risk marker for infection. The evidence from the literature is discussed, and the criteria for causal inference proposed by Sir Austin Bradford Hill are applied. GOAL: To evaluate the strength of the association between GUD and infection by HIV. STUDY DESIGN: Case-control, cross-sectional, and cohort studies that examined the association between HIV seroconversion and GUD were chosen from the literature. Twenty-seven epidemiologic studies were selected for analysis, many of which reported separate analyses of the association between HIV infection and herpes simplex virus infection, syphilis, or nonspecified GUD. The studies were analyzed to investigate the magnitude of association between GUD and HIV, and the evidence evaluated using Hill's criteria. RESULTS: Approximately two thirds of the analyses reported a statistically significant association between GUD and HIV infection. Fourteen studies reported 29 separate analyses using a case-control design, 18 of which reported a statistically significant association between GUD (GUD, herpes, and syphilis) and HIV infection, four analyses were of varying significance depending on the analytical technique used, and seven were nonsignificant. Thirteen studies reported 23 separate longitudinal analyses that used a nested case-control or cohort design: 11 reported a significant association, 11 had nonsignificant findings, and results of one study varied. No study reported a statistically significant negative association. When applying the literature to Hill's criteria, all nine criteria for causal inference were met, providing additional evidence that genital ulcers are associated with an increased risk for the development of HIV infection. CONCLUSIONS: The published evidence suggests that GUD increases the risk for HIV acquisition. Few studies, however, have examined carefully the temporal association between preexisting GUD and subsequent HIV acquisition. The analyses that simultaneously controlled for additional risks for HIV infection, such as lifetime sex partners or history of injection drug use, report a generally lower risk for HIV associated with GUD. It is likely that studies that adequately control for risk factors will find a lower risk associated with GUD than was reported in the literature earlier in the HIV epidemic. Future research needs and the problems associated with conducting these types of studies are discussed.

Case-Control Studies↗

PubMed1995

The lack of causality between asbestos and colorectal cancer.

To evaluate a potential causal relationship between asbestos exposure and the risk of colorectal cancer, 30 cohort studies published in English were reviewed and analyzed. The latest report of each cohort up through 1993 was used. The outcome measure was the standardized morbidity (incidence) or mortality ratio (SMR). Summary SMRs were examined by type of cohort registration, type of work, type of asbestos, latency from onset of exposure to period of risk, and incidence only. The overall relative risk was 0.99 for all 30 studies. The evidence does not meet the important criteria for a judgment of causality because the relative risk is not consistently elevated, weak in the two studies with a statistically significant elevation of SMR, and limited data do not support a dose-response relationship.

Asbestos↗

PubMed2006

Causal attributions and health behavior choices among stroke and transient ischemic attack survivors.

To reduce the risk of a recurring event in patients who have suffered an initial stroke or transient ischemic attack (TIA), nurses are challenged with implementing and promoting changes in lifestyle and adherence to treatment regimens. Assessing patients' beliefs about the cause of the stroke or TIA is important to understanding their subsequent health behaviors. This study describes the causal attributions and health behavior choices of 9 participants following a stroke or TIA. Attributions were categorized as internal or external and cross-tabulated by controllability. The attributions were compared with health behavior choices. All participants attempted to make causal attributions, both internal (e.g., anxiety, hypertension, lifestyle) and external (e.g., stress, fate). Those making external attributions demonstrated poorer health behavior choices than those making internal attributions; controllability had no influence on behavior. Patients diagnosed more than 6 months before the study tended to make more external attributions. The results can help nurses understand the beliefs that drive the health behavior choices made by stroke and TIA survivors and guide them in tailoring prevention strategies and engaging patients in preventive activities.

Adult↗

PubMed2026

The bidirectional genetic causality between immunocyte phenotypes and dilated cardiomyopathy: A bidirectional Mendelian randomization study.

The association between immunocyte phenotypes and dilated cardiomyopathy (DCM) has been explored, however the exact pathogenesis of the relationship between immune cells and DCM is unclear. This bidirectional two-sample Mendelian randomization (MR) research aims to further validate the causal link between 731 immunocyte phenotypes and DCM. Summary statistics from a genome-wide association study data of individuals with European ancestry were utilized, including 1444 DCM cases and 353,937 controls, as well as 3757 European adults for the 731 immunocyte phenotypes. Causal effects were estimated using inverse variance weighted, MR-Egger regression, weight median estimator, weighted mode, and simple mode. Sensitivity analysis was conducted to confirm data robustness and feasibility. Based on the inverse variance weighted findings, 14 immunocyte phenotypes were risk factors for DCM (P < .05, odds ratio [OR] > 1), while 15 immunocyte phenotypes exhibited a protective effect on DCM (P < .05, OR < 1). The results of reverse MR analysis suggested evidence that DCM occurrence might elevate the levels of 17 immunocyte phenotypes (P < .05, OR > 1) and decrease the levels of 9 immunocyte phenotypes (P < .05, OR < 1). Our research indicated that CD28 on secreting regulatory T cell could mitigate the occurrence of DCM, and reciprocally, the progression of DCM could reduce the level of CD28 on secreting regulatory T cell. This study confirmed the bidirectional genetic predictive relationship between immunocyte phenotypes and DCM, underscoring the complex interplay between DCM and the immune system.

Cardiomyopathy, Dilated↗

PubMed2004

Granger causality and information flow in multivariate processes.

The multivariate versus bivariate measures of Granger causality were considered. Granger causality in the application to multivariate physiological time series has the meaning of the information flow between channels. It was shown by means of simulations and by the example of experimental electroencephalogram signals that bivariate estimates of directionality in case of mutually interdependent channels give erroneous results, therefore multivariate measures such as directed transfer function should be used for determination of the information flow.

Algorithms↗

PubMed2006

A softmin-based neural model for causal reasoning.

This paper extends a neural model for causal reasoning to mechanize the monotonic class. Hence, the resulting model is able to solve multiple, varied causal problems in the open, independent, incompatibility and monotonic classes. First, additivity between causes is formalized as a fuzzy AND-ing process. Second, an activation mechanism called the "softmin" is developed to solve additive interactions. Third, the softmin is implemented within a neural architecture. Experimental results on real-world and artificial problems reveal a good performance of the model and should stimulate future research.

Algorithms↗

PubMed2003

The role of the children of twins design in elucidating causal relations between parent characteristics and child outcomes.

BACKGROUND: Determination of causal connections between parental measures and child outcomes using typical samples is limited by the inability to account for all confounds, both environmental and genetic. This paper discusses the strength of the Children of Twins (COT) design to highlight the role of specific environments. METHODS: A new analytical model is presented which helps differentiate and quantify the environmental and genetic processes underlying associations between family-level risk factors and child adjustment. In order to illustrate the COT design, the relation between smoking during pregnancy and child birth weight (BW) is examined in a sample of female twins and their children from Norway and the United States. RESULTS: The results illustrate that smoking during pregnancy is influenced by genetic factors. However, the Children of Twins model supports the claim that smoking during pregnancy has a direct environmental influence on BW and that genetic and shared environmental confounds cannot account for the association. CONCLUSIONS: An assessment of the strengths and limitations of the Children of Twins design and a comparison with other research strategies suggest that the design plays a unique role in the study of developmental psychology and psychopathology. Finally, the authors describe how methodological advances and future applications of the design will provide additional insight into the causal processes underlying children's adjustment to environmental stimuli.

Adult↗

PubMed2003

A causal proportional hazards estimator for the effect of treatment actually received in a randomized trial with all-or-nothing compliance.

Survival data from randomized trials are most often analyzed in a proportional hazards (PH) framework that follows the intention-to-treat (ITT) principle. When not all the patients on the experimental arm actually receive the assigned treatment, the ITT-estimator mixes its effect on treatment compliers with its absence of effect on noncompliers. The structural accelerated failure time (SAFT) models of Robins and Tsiatis are designed to consistently estimate causal effects on the treated, without direct assumptions about the compliance selection mechanism. The traditional PH-model, however, has not yet led to such causal interpretation. In this article, we examine a PH-model of treatment effect on the treated subgroup. While potential treatment compliance is unobserved in the control arm, we derive an estimating equation for the Compliers PROPortional Hazards Effect of Treatment (C-PROPHET). The jackknife is used for bias correction and variance estimation. The method is applied to data from a recently finished clinical trial in cancer patients with liver metastases.

Algorithms↗

PubMed2006

Evidence for a causal association between oral polio vaccine and transverse myelitis: A case history and review of the Literature.

A 6-month-old boy developed transverse myelitis 7 days after the receipt of oral polio vaccine (OPV). A paediatric neurologist confirmed the diagnosis when the boy was aged 9 years. The boy had received his first scheduled OPV at the age of 4 months and had developed immunity to serotypes 1 and 2 but not to serotype 3. A poliovirus type 3 was isolated from stool and throat specimens collected from the boy in the first 2 days after symptom onset. This was shown, in a World Health Organization accredited laboratory, to be a vaccine strain by nucleic acid probe hybridiztion and enzyme-linked immunosorbent assay. The boy subsequently developed immunity to poliovirus serotype 3. It is accepted that poliovirus infection can present occasionally as transverse myelitis. This is estimated to occur in 1:125-1:800 cases. It is also accepted that OPV can cause vaccine-associated paralytic polio with a frequency of approximately one case per 2.5 million doses of OPV distributed. It seems feasible therefore that OPV could cause transverse myelitis with a frequency of 1 in 300 million to one in two billion doses distributed. In a 1993 report from the Institute of Medicine of the National Acadamies of the United States pertaining to vaccine safety, theoretical criteria were advanced for the establishment of a causal relationship between a vaccine and a clinical outcome. The clinical history and laboratory results in this case satisfy these criteria, providing plausible evidence for the causal link between OPV and transverse myelitis.

Causality↗

PubMed1994

Causality orientations, failure, and achievement.

Two studies examined similarities between Deci and Ryan's (1985) causality orientations theory and Dweck and Leggett's (1988) social-cognitive theory of achievement. Study 1 examined the conceptual similarity between the individual difference measures central to the two theories. It was shown that autonomous college students are likely to adopt learning goals and report high confidence in their academic abilities; controlled students are likely to adopt performance goals and to report high levels of confidence in their ability; and impersonal students are likely to possess the classic helpless pattern of performance goals and low confidence in their academic abilities. Study 2 examined whether causality orientations, like Dweck's measures of goals and confidence, moderate the impact of failure feedback on motivation as measured in persistence and performance. The results suggested that autonomous individuals respond to failure in a mastery-oriented fashion, whereas impersonal individuals respond in a helpless manner. The response of controlled individuals to failure parallels that of people described as ego-involved or reactive.

Achievement↗

PubMed1993

Causal attributions and post-traumatic stress in adolescents.

The aim of the present study was to explore the relationship between causal attributions made by adolescent survivors of the Jupiter cruise ship sinking, and post-traumatic symptomatology in the year following disaster. Evidence is presented that more internal causal attributions for negative and uncontrollable events during the incident are associated with greater post-traumatic stress one year later. The findings are discussed with reference to an attributional model of shame.

Adolescent↗

PubMed1997

Causality assessment of the acute health complaints reported in association with oxygenated fuels.

In some areas where oxygenated fuel programs have been implemented, there have been wide-spread complaints of non-specific health effects attributed to the gasoline. There are a number of hypotheses that can account for this apparent association. This paper examines the hypothesis that the use of oxy-fuel (either oxygenated gasoline or reformulated gasoline) results in exposure of the general population to one or more chemicals at concentrations that cause toxicologic injury. Although several oxygenates can be used in oxy-fuels, this analysis focuses on MTBE because it is the most widely used oxygenate and because the database of relevant toxicologic data is greatest for this oxygenate. The causal assessment is based on an evaluation of the qualitative and quantitative plausibility that oxygenated fuel-related exposures have toxicological effects, and the epidemiologic studies that directly test the hypothesis that the use of oxygenated fuels causes adverse health effects. The plausibility that chemical exposures related to oxy-fuel use cause toxicological effects is very low. This determination is based on consideration of the exposure-response and time-action profiles for relevant toxicological effects of MTBE in animals, experimental MTBE exposure studies in humans, and the possibility that the addition of MTBE to gasoline results in toxicologically significant qualitative and/or quantitative changes in gasoline-related exposures. Similarly, the epidemiologic studies of oxy-fuel exposed cohorts do not support a causal relationship between oxy-fuel use and adverse health effects. Although the data are insufficient to rule the possibility of unique sensitivity in a small segment of the population, the strength of the evidence and the availability of other more plausible explanations for the health complaints reported in association with oxy-fuels support a high degree of confidence in the conclusion that MTBE-containing oxygenated fuels are not the cause of acute toxicity in the general population.

Air Pollutants↗