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Results for “causal inference”

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PubMed2006

Clustering of behavioural risk factors and compliance with clinical preventive recommendations in Spain.

OBJECTIVE: To examine the relationship between the clustering of behavioural risk factors and compliance with clinical preventive practices. METHOD: Cross-sectional study using a telephone interview of a sample of 16043 persons, representative of the population aged 18-64 years in the Madrid Region (Spain). The criteria for providing clinical preventive services were based on recommendations issued by the Spanish Society for Family and Community Medicine. Analyses were performed using logistic regression with adjustment for age, education, social class and year of interview. RESULTS: A positive dose-response association was observed between the number of behavioural risk factors (tobacco smoking, hazardous alcohol drinking, leisure-time sedentariness and unbalanced diet) and non-compliance of recommendations for blood-pressure and cholesterol testing, and for cytology and mammography screening (P < 0.001). Compared to subjects with no behavioural risk factors, those with all four risk factors showed a higher frequency of non-compliance of blood pressure assessment: OR = 2.5 (95% CI: 1.6, 3.8) in men and 2.7 (1.5, 4.8) in women, and cholesterolaemia testing: OR = 2.6 (1.8, 3.9) in men and 2.7 (1.5, 5.1) in women. Furthermore, among women, the presence of these four risk factors was also associated with a higher frequency of non-performance of cytology: OR = 6.4 (2.8, 14.8) and mammography screening: OR = 10.2 (2.1, 49.8). However, as it is a cross-sectional study, we do not know the direction of this relationship, therefore, any causal inference should be made with caution. CONCLUSIONS: Clustering of behavioural risk factors is associated with greater non-compliance with recommendations for both blood pressure and cholesterolaemia testing, and for cytology and mammography screening.

Adolescent↗
PubMed2003

Models of causation and the semantics of causal verbs.

This research examines the relationship between the concept of CAUSE as it is characterized in psychological models of causation and the meaning of causal verbs, such as the verb cause itself. According to focal set models of causation (; ), the concept of CAUSE should be more similar to the concepts of ENABLE and PREVENT than either is to each other. According to a model based on theory of force dynamics, the force dynamic model, the concepts of CAUSE, ENABLE, and PREVENT should be roughly equally similar to one another. The relationship between these predictions and the meaning of causal verbs was examined by having participants sort causal verbs and rate them with respect to the dimensions specified by the two models. The results from five experiments indicated that the force dynamic model provides a better account of the meaning of causal verbs than do focal set models of causation. Implications for causal inference and induction are discussed.

Humans↗
PubMed2000

Exogenous corticosteroids and major depression in the general population.

OBJECTIVE: An existing literature suggests that corticosteroid exposures are associated with an elevated level of depressive symptoms in various clinical populations. The objective of this study was to evaluate this association in a general population sample. METHODS: Data from a large-scale Canadian health survey were used in this analysis. The survey sample included 73,402 subjects over the age of 12 from the general Canadian population. The survey interview included a short-form version of the Composite International Diagnostic Interview (CIDI) section evaluating major depressive episodes. All estimates were weighted to account for unequal selection probabilities, and variance estimates were calculated using methods accounting for the survey design. RESULTS: A statistically significant elevation in major depression prevalence was observed in corticosteroid-treated subjects. The estimated 12-month period prevalence of major depression was approximately three times as high in corticosteroid treated vs. non-treated subjects irrespective of age, gender and perceived health. CONCLUSIONS: In the general population, persons taking corticosteroids have a higher frequency of major depression than non-exposed subjects. Because this was an analysis of cross-sectional survey data, causal inference is not possible. However, the existence of an epidemiological association, in conjunction with information from the broader literature, suggests that corticosteroid exposure may be a determinant of depressive disorders in the general population.

Adrenal Cortex Hormones↗
PubMed2002

Prenatal prescription of macrolide antibiotics and infantile hypertrophic pyloric stenosis.

OBJECTIVE: To assess the association between prenatal antibiotics, including erythromycin, and infantile hypertrophic pyloric stenosis in a large cohort of infants. METHODS: This was a retrospective cohort study of births to women enrolled in Tennessee Medicaid/TennCare, 1985-1997. Prescriptions for erythromycin, nonerythromycin macrolides, and other antibiotics were identified from pharmacy files linked with birth certificate files. The primary study outcome was development of pyloric stenosis in the infant, identified from linked hospital discharge diagnosis and surgical procedure codes. RESULTS: The cohort included 260,799 mother/infant pairs. Among these women, 13,146 filled prescriptions for erythromycin (50.4 per 1000), and 621 filled prescriptions for nonerythromycin macrolides (2.4 per 1000). There was no association with prenatal erythromycin prescription and infantile hypertrophic pyloric stenosis either after 32 weeks' gestation (adjusted odds ratio 1.17, 95% confidence interval, 0.84, 1.64, P =.33) or at any time during pregnancy (adjusted odds ratio 1.15, 95% confidence interval 0.84, 1.56, P =.36). There was an association between maternal prescriptions for nonerythromycin macrolides and infantile hypertrophic pyloric stenosis (adjusted odds ratio 2.77, 95% confidence interval 1.22, 6.30, P =.01). CONCLUSION: The hypothesized association between erythromycin and infantile pyloric stenosis was not seen. Causal inference from the association between prenatal nonerythromycin macrolides and infantile hypertrophic pyloric stenosis is limited by the small number of affected children and the evidence of other differences between users of nonerythromycin macrolides and controls.

Adult↗
PubMed2000

Association between DQB1 and cervical cancer in patients with human papillomavirus and family controls.

OBJECTIVE: The role of human leukocyte antigen (HLA) DQB1 alleles and human papillomavirus (HPV) as contributing factors to invasive cervical cancer was investigated. To overcome problems of misleading causal inferences common in traditional case-control studies, a family-based test, the transmission/disequilibrium test, was used. METHODS: Ninety-six patients with pathologically confirmed invasive cervical cancer were ascertained. Human papillomavirus types were determined in 80 patients, of whom 81.25% were HPV-positive, and 18.75% were HPV-negative. Deoxyribonucleic acid was extracted from samples, taken from patients and their parents, and sequenced to determine DQB1 genotypes. Nuclear family data were used to test whether the DQB1 locus is associated with invasive cervical cancer while controlling for high-risk HPV-positive patients. The transmission/disequilibrium test evaluates whether the frequency of transmission of parental marker alleles to their affected offspring deviates from the expected Mendelian frequency of 50%. RESULTS: The HLA DQB1 locus showed evidence for allelic association with invasive cervical cancer in high-risk HPV-positive patients (P = .006). The transmission/disequilibrium test showed that the DQB1*0303 allele was transmitted to high-risk HPV patients more often than expected by chance, chi2(1) = 8.0, P = .005 (P = .035 when correcting for multiple tests). Tests of association were negative when applied to all 96 patients, irrespective of HPV status. No significant differences were found in the distribution of the DQB1 alleles among HPV-positive patients compared with those who were HPV-negative, indicating that HLA alleles are not associated with susceptibility to HPV infection. CONCLUSION: These results suggest that the DQB1*0303 allele increases the risk for invasive cervical cancer in women who are HPV-positive.

Adenocarcinoma↗
PubMed2001

Limitations of controlled experimental systems as models for natural systems: a conceptual assessment of experimental practices in biogeochemistry and soil science.

Experimental systems in which phenomena are studied under controlled conditions allow scientists to infer causal relationships from observable effects. When investigating ecosystems, however, scientists face complex systems. The conventional approach is to divide the system into conceptual units and to prepare experimental systems accordingly. Experimental systems are used as models for ecosystems: initially, scientists assume an analogy between the experimental system and ecosystem, then encode the experimental system into a formal system by measuring variables, and decode statements from the formal system to the ecosystem. We distinguish three types of experimental systems, i.e. laboratory, container and field set-ups, further divided into seven subtypes. Starting from the premises of experimental systems, we comment on the possibilities and limitations of experimentally derived causal relationships and on their significance for ecosystem understanding and prediction, illustrated by examples from soil science and the environmental sciences. Experimental set-ups have a characteristic duration, degree of structural integrity, internal variability and boundaries, which relate to conceptual closure and experimental control: control tends to be maximum on short time scales, in homogeneous set-ups with analytical boundaries, and in systems with few parameters to be observed. Complexity is increased at the expense of control. The higher the degree of manipulation, however, the better is reproducibility, but the larger is the deviation from unique ecosystems with their infinite number of factors. The material realization of closed systems is preceded by a conceptual closure of the system. Closure is relative to the domain of phenomena of interest, the theory and the list of variables selected by the scientist. Successful decoding from experimental systems to ecosystems largely depends on the validity of the chosen analogy. Laboratory systems are idealized systems which contain a limited number of a priori defined variables, and which are shielded from environmental influences. In contrast, ecosystems are materially and conceptually open, non-stationary, historical systems, in which system-level properties can emerge, and in which variables are produced internally. We conclude that when conducting experiments, causal factors can be identified, but that causal knowledge derived from insufficiently closed systems is invalid. In ecosystems, innumerous factors interact, which may enhance, reduce or neutralize the effect of an experimentally determined factor. Thus, experimental model systems need to be evaluated for concrete, well-defined ecosystems with a concrete history. Increasingly detailed studies of isolated phenomena in the laboratory will probably not contribute much to ecosystem-level understanding. When conducting experiments, scientists should aim at the maximum degree of complexity they can actually handle and they should justify the chosen analogy.

Ecosystem↗
PubMed1997

A nested case-control study of non-Hodgkin lymphoma and serum organochlorine residues.

BACKGROUND: The steady worldwide increase in the incidence of non-Hodgkin lymphoma during the past few decades remains mostly unexplained. Several studies suggest that there may be an association between the agricultural use of the organochlorine 1,1,1-trichloro-2,2'bis(p-chlorophenyl)ethane (DDT) and increased risk of non-Hodgkin lymphoma. We have investigated the association between risk of non-Hodgkin lymphoma and body burden of selected organochlorines in the general population in a nested case-control study. METHODS: We measured prediagnostic serum concentrations of DDT, its metabolites, and other organochlorines, including polychlorinated biphenyls (PCBs), in 74 cases of non-Hodgkin lymphoma and 147 matched controls identified from a prospective cohort of 25,802 adults, established in 1974 in Washington County, Maryland, USA. We report results for total lipid-corrected serum concentrations of DDT and total PCBs. FINDINGS: There was a strong dose-response relation between quartiles of total lipid-corrected serum PCB concentrations and risk of non-Hodgkin lymphoma overall (odds ratios by quartile: 1.0; 1.3 [95% CI 0.5-3.3]; 2.8 [1.1-7.6]); and 4.5 [1.7-12.0]; p for trend = 0.0008) and separately in men and in women. There was also evidence suggesting that seropositivity for the Epstein-Barr virus early antigen potentiated the effects of serum PCBs. By contrast, total lipid-corrected serum concentrations of DDT were not associated with risk of non-Hodgkin lymphoma. INTERPRETATION: These results should be regarded as hypothesis-generating. Before causal inferences can be made about exposure to PCBs and increased risk of non-Hodgkin lymphoma, our findings require replication and the biological plausibility of the association needs further investigation.

Adult↗
PubMed2003

(Unlearned) lessons from John Graunt and Kenneth Rothman: a "CLASSic" example.

This commentary reviews the work of John Graunt and Kenneth J. Rothman on statistical significance and the need for prespecification of study end points. The authors argue that it is dangerous to substitute oversimplifications based exclusively on whether a result has reached statistical significance for a rational process of causal inference. An example is given based on the Celecoxib Long-term Arthritis Safety Study.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Lower self-reported depression in patients with erectile dysfunction after treatment with sildenafil.

BACKGROUND: Depressive symptoms in men with erectile dysfunction (ED) may improve under successful ED treatment. Self-reported depressive symptoms were compared in men with ED after sildenafil treatment to a group of untreated patients. METHODS: In an open study, self-reported depressive symptoms of 54 men after successful treatment with sildenafil (>4 weeks) and 51 men awaiting ED treatment were investigated with the Center of Epidemiologic Studies-Depression Scale (CES-D). CES-D items were subjected to an exploratory factor analysis and group differences in CES-D items and factors were analyzed. RESULTS: Groups were comparable with respect to demographic characteristics and illness duration. CES-D total scores were lower in the group treated with sildenafil. Substantial differences were found in favor of the group treated with sildenafil, particularly in scores on a "positive affect" factor. CONCLUSIONS: The findings emphasize the relevance of depression associated with ED and the importance of effective ED treatment. Although depression was generally low in this sample, hedonistic aspects were substantially enhanced in the group of ED patients after sildenafil treatment. LIMITATIONS: The open and cross-sectional study design does not permit causal inference. Selection bias and motivational aspects to participate in the study can not completely be ruled out.

Aged↗
PubMed2000

Coping and medication adherence in bipolar disorder.

BACKGROUND: Effective treatment of bipolar disorder depends on medication adherence, yet few correlates of adherence have been identified. The pleasure experienced during some manic episodes may render some individuals reluctant to adhere to medications that reduce these 'highs'. Clinical observers identify denial of the severity or existence of illness as common to both bipolar disorder and addiction. The Alcoholics Anonymous model promotes acceptance as a pathway to abstinence adherence. This report hypothesized that acceptance coping would correlate positively and denial coping would correlate inversely with adherence to mood-stabilizing medication among individuals with bipolar disorder. METHODS: Thirty-two participants diagnosed with bipolar I disorder were administered scales from the Brief COPE and an adherence self-report measure. RESULTS: Consistent with hypotheses, curvilinear relationships between acceptance and denial with adherence were detected, suggesting that low levels of acceptance and high levels of denial undermine medication adherence. LIMITATIONS: Given the cross-sectional, naturalistic design of the study, no causal inferences can be made. CONCLUSIONS: The results uncover links between coping styles and adherence in a psychiatric population. The link between acceptance-denial coping, and mature, self-supportive behavior may point the way towards more effective psychosocial interventions.

Adaptation, Psychological↗
PubMed2000

The relationship between psychosocial work characteristics and low back pain: underlying methodological issues.

OBJECTIVE: To evaluate the current epidemiological evidence linking psychosocial work characteristics with low back pain. BACKGROUND: Psychosocial work characteristics have been widely evaluated as potential risk factors for low back injury. However, studies with different study populations and using various types of measures have had conflicting results. METHODS: This review is the most extensive to date, reviewing 66 articles that have provided empirical evidence about the relationship between psychosocial work characteristics and initial reporting of lower back pain. The studies are reviewed with an emphasis on certain methodological issues: controlling for potential confounding; timing of the data collection; and measurement of the exposures and outcomes. RESULTS: The results of this review suggest that controlling for potential confounding from occupational biomechanical demands had a large influence on the associations found between psychosocial work characteristics and lower back pain. In addition, the use of accurate and reliable measures for the occupational exposures (biomechanical and psychosocial) and the lower back pain outcomes appears to influence the strength of the associations found between psychosocial work characteristics and lower back pain. CONCLUSION: Given the methodological concerns discussed in this review, it is difficult to draw strong causal inferences from this literature. However, it does appear that psychosocial characteristics are related to some lower back pain outcomes, and that employees' reactions to psychosocial work characteristics (e.g., job dissatisfaction and job stress) are more consistently related to lower back pain than are the psychosocial work characteristics themselves (e.g., work overload, lack of influence over work, quality of relationships with coworkers). RELEVANCE: This review attempts to identify and address methodological issues in the literature evaluating the relationship between psychosocial work characteristics and lower back pain. Implications for future research are presented.

Humans↗
PubMed2002

Environmental epidemiology: basics and proof of cause-effect.

Bringing epidemiology and toxicology together to better understand cause and effect relationships requires attention to several interconnected problems: problems of commitment, complexity, and of communication. The most fundamental of these is commitment as it is reflected in the basic purpose of environmental epidemiology. The purpose of epidemiology is not to prove cause-effect relationships, and not only because scientific proof is elusive. The purpose of epidemiology is to acquire knowledge about the determinants and distributions of disease and to apply that knowledge to improve public health. A key problem, therefore, is how much and what kinds of evidence are sufficient to warrant public health (typically preventive) actions? The assessment of available evidence lays the foundation for the problem of complexity: relevant evidence arrives from toxicologic and epidemiological investigations, and reflects the acquisition of knowledge from many levels of scientific understanding: molecular, cellular, tissue, organ systems, complete organisms (man and mouse), relationships between individuals, and on to social and political processes that may impact human health. How to combine evidence from several levels of understanding will require the effective communication of current methodological practices. The practice of causal inference in contemporary environmental epidemiology, for example, relies upon three largely qualitative methods: systematic narrative reviews, criteria-based inference methods, and (increasingly) meta-analysis. These methods are described as they are currently used in practice and several key problems in that practice are highlighted including the relevance to public health practice of toxicological evidence.

Animals↗
PubMedDate not supplied

Impact of HIV risk and infection and the role of prevention services.

Blood-borne infection associated with injection drug use is a significant cause of morbidity and mortality. Over the last decade, HIV infection and its clinical sequelae have had a significant impact on research and interventions involving injecting drug users (IDUs) in the United States and elsewhere. Discussed are some of the major intervention options for reducing blood-borne infections in general and HIV in particular. The use of multiple interventions is considered within the community context in which both IDUs and service providers operate. Intervention options discussed include treatment for drug dependence; voluntary and confidential HIV testing and counseling; community health outreach; bleach distribution; and easy, legal access to needles and syringes through pharmacy sales and needle exchange programs. Many surveillance and evaluative studies have examined multiple intervention efforts that include all or some of these program components and suggest positive outcomes. However, these studies tend to be limited by experimental designs that restrict attribution of causal inference. Examples of such programs in the United States and abroad are examined in terms of their potential for reducing HIV risk behaviors and averting new infections. The article concludes that diversity among AIDS prevention programs, rapid deployment (at earlier stages of epidemics), and effective coordination (minimization of interagency conflicts) are important factors in successful AIDS prevention programming and attaining disease prevention objectives.

Blood-Borne Pathogens↗
PubMed2003

A population-based cohort study of mortality among adults prescribed paracetamol in Denmark.

OBJECTIVE: We examined overall and cause-specific mortality in a population-based cohort of individuals prescribed paracetamol. We evaluated rates of death due to liver and renal disease, cancer, and other major causes of death. METHOD: Using the population-based pharmacoepidemiology prescription database of North Jutland County, Denmark, we identified nearly 50,000 persons receiving prescriptions for paracetamol from 1989 to 1995 and evaluated mortality through 1996. Standardized mortality ratios (SMRs) for 18 specific causes of death were computed for persons prescribed paracetamol compared with persons among the general population of the county. RESULTS: SMRs were elevated regardless of cause of death, with a nearly doubled overall death rate among persons prescribed paracetamol. The mortality ratios were highest within 1 year of paracetamol prescription and tended to decline with increasing follow-up, especially for cancers. The magnitudes of the excess mortality risks for liver and renal diseases were not materially higher than for other causes of death. CONCLUSION: Paracetamol is a first-line analgesic for patients with a wide variety of chronic or serious illnesses and therefore is associated with increased rates of nearly all causes of death. The findings are an example of confounding by indication. Paracetamol may be a drug most prone to this form of bias in pharmacoepidemiologic studies. Future observational studies reporting adverse effects of paracetamol must thoroughly evaluate confounding by indication before making causal inferences.

Acetaminophen↗
PubMed1999

Guidelines for authors of books and papers on complementary medicine.

Writing about complementary medicine, whether intended for book or journal publication, has often suffered from three flaws: inadequate attention to the origin and nature of knowledge claims; careless use of problematic concepts such as 'holistic' or 'natural' and poor application of basic principles of good scholarship. In this paper I present guidelines to promote better writing. With respect to knowledge claims, authors need to be explicit about the origin of the claim; that is, the reasons why they believe it to be true. Many books and papers on complementary medicine are flawed because their authors avoided explaining why they have made particular claims. Claims can be justified by using personal experience or by quoting scientific research. When using personal experience, authors need to: describe the practitioners concerned; use generalities about practitioners with care and be wary when referring to 'classical' or 'traditional' practitioners. When quoting scientific research, authors should: cite references and use these sparingly and specifically; avoid 'secondary sourcing', reliance on abstracts and the referencing of authorities; use 'weasel words' ('may' or 'can') with extreme care; think carefully about causal inferences and take care with laboratory-based research. Many of the concepts found in books and papers on complementary medicine are used rather carelessly. Concepts such as holism or 'natural' medicine, or even the concept of 'complementary' and 'conventional' medicine, are often taken to have simple and obvious meanings. Yet these concepts are extremely slippery and open to differing interpretations, especially if they are used with insufficient care. Authors should apply basic principles of good scholarship by displaying thoroughness and attention to detail; reflecting on the validity of each point made; reflecting on the limitations of their arguments and maintaining a level of disinterestedness. However, authors should avoid trying to sound academic for the sake of it: the use of long words, obscure jargon and dense and lengthy prose does not make a work scholarly.

Authorship↗
PubMed2003

A report of the functional connectivity workshop, Dusseldorf 2002.

This report provides a commentary on the issues presented and discussed at the recent "Functional Brain Connectivity" workshop, held in Dusseldorf, Germany. The workshop brought together researchers using different approaches to study connectivity in the brain, providing them with an opportunity to share conceptual, mathematical, and experimental ideas and to develop strategies and collaborations for future work on functional integration. The main themes that emerged included: (1) the importance of anatomical knowledge in understanding functional interactions the brain; (2) the need to establish common definitions for terms used across disciplines; (3) the need to develop a satisfactory framework for inferring causality from functional imaging and EEG/MEG data; (4) the importance of analytic tools that capture the dynamics of neural interactions; and (5) the role of experimental paradigms that exploit the functional imaging of perturbations to cortical interactions.

Animals↗
PubMed2000

Bacterial vaginosis.

Bacterial vaginosis is the most common cause of vaginitis, affecting over 3 million women in the United States annually. Depopulation of lactobacilli from the normal vaginal flora and overgrowth of Gardnerella vaginalis and other anaerobic species are the presumed etiology. To date, no scientific evidence shows that bacterial vaginosis is a sexually transmitted disease. Malodorous vaginal discharge is the most common symptom. Differential diagnoses include trichomoniasis, moniliasis, and allergic or chemical dermatitis. The diagnosis is confirmed when at least three of the following four findings are present (Amsel's criteria): 1) thin, homogenous discharge, 2) pH greater than 4.5, 3) positive amine test, and 4) presence of clue cells. The sensitivity and positive predictive value are both 90%. Vaginal Gram stain is also reliable and allows for permanent record. Cultures are nonspecific because G. vaginalis resides in normal vaginal flora as well. Papanicolaou smears are not particularly sensitive, but their positive predictive value is very high. The Centers for Disease Control and Prevention recommend three treatment regimens in nonpregnant patients: oral metronidazole (500 mg twice daily for 7 days), intravaginal 2% clindamycin cream (one applicatorful at bedtime for 7 days), or intravaginal metronidazole gel (one to two applicatorfuls per day for 5 days). Alternative regimens include a single 2-g oral dose of metronidazole or a 7-day course of oral clindamycin, 300 mg twice daily. The association between bacterial vaginosis and adverse pregnancy outcomes has satisfied many criteria for a causal inference. Treatment of bacterial vaginosis in women with previous history of preterm labor results in fewer preterm deliveries than in untreated women from the same population.

Journal Article↗
PubMed1988

Height of women, twinning and breast cancer: epidemiological evidence of a relationship.

A comparison was made of the stature of women, twinning rates, and breast cancer mortality for 32 countries. As height increased, so did twinning and breast cancer mortality (P less than 0.005). Dizygotic twinning and breast cancer increased sharply with the mean height of the female population. With due caution in drawing causal inferences when uncontrolled confounding variables are present, it is suggested that these findings are an evolutionary consequence of the high mortality found in twin pregnancy.

Body Height↗