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PubMed2004

Evaluating heterogeneity in cumulative meta-analyses.

BACKGROUND: Recently developed measures such as I2 and H allow the evaluation of the impact of heterogeneity in conventional meta-analyses. There has been no examination of the development of heterogeneity in the context of a cumulative meta-analysis. METHODS: Cumulative meta-analyses of five smoking cessation interventions (clonidine, nicotine replacement therapy using gum and patch, physician advice and acupuncture) were used to calculate I2 and H. These values were plotted by year of publication, control event rate and sample size to trace the development of heterogeneity over these covariates. RESULTS: The cumulative evaluation of heterogeneity varied according to the measure of heterogeneity used and the basis of cumulation. Plots produced from the calculations revealed areas of heterogeneity useful in the consideration of potential sources for further study. CONCLUSION: The examination of heterogeneity in conjunction with summary effect estimates in a cumulative meta-analysis offered valuable insight into the evolution of variation. Such information is not available in the context of conventional meta-analysis and has the potential to lead to the development of a richer picture of the effectiveness of interventions.

Acupuncture↗
PubMed2006

Are there differences in all-cause and coronary heart disease mortality between immigrants in Sweden and in their country of birth? A follow-up study of total populations.

BACKGROUND: Mortality from cardiovascular diseases is higher among immigrants than native Swedes. It is not clear whether the high mortality persists from the country of birth or is a result of migration. The purpose of the present study was to analyse whether all-cause and coronary heart disease mortality differ between immigrants in Sweden and in the country of birth. METHODS: Two cohorts including the total population from Swedish national registers and WHO were defined. All-cause and CHD mortality are presented as age-adjusted incidence rates and incidence density ratios (IDR) in eight immigrant groups in Sweden and in their country of birth. The data were analysed using Poisson regression. RESULTS: The all-cause mortality risk was lower among seven of eight male immigrant groups (IDR 0.39-0.97) and among six of eight female immigrant groups (IDR 0.42-0.81) than in their country of birth. The CHD mortality risk was significantly lower in male immigrants from Norway (IDR = 0.84), Finland (IDR = 0.91), Germany (IDR = 0.84) and Hungary (IDR = 0.59) and among female immigrants from Germany (IDR = 0.66) and Hungary (IDR = 0.54) than in their country of birth. In contrast, there was a significantly higher CHD mortality risk in male immigrants from Southern Europe (IDR = 1.23) than in their country of birth. CONCLUSION: The all-cause mortality risk was lower in the majority of immigrant groups in Sweden than in their country of birth. The differences in CHD mortality risks were more complex. For countries with high CHD mortality, such as Finland and Hungary, the risk was lower among immigrants in Sweden than in their country of birth. For low-risk countries in South Europe, the risk was higher in immigrants in Sweden than in South Europe.

Age Distribution↗
PubMed1995

The P1 component of the middle latency auditory evoked potential predicts a practice effect during clinical trials in Alzheimer's disease.

Thirty-five patients with probable Alzheimer's disease who were enrolled in an experimental drug trial of linopirdine underwent repeated testing that included recording the middle latency auditory evoked potential (MLAEP), the Mini-Mental State Examination (MMSE), and the Alzheimer's Disease Assessment Scale Cognitive Subscale (ADASCOG). Patients lacking the P1 component of the MLAEP exhibited a significantly greater decline in cognitive function as measured by the ADASCOG over 56 weeks. This decline appeared to be due to a less robust practice effect, which was maximal in all patients at 16 weeks. At the end of 56 weeks the entire group of patients was near baseline with respect to the ADASCOG. This lack of the annualized decline expected from other longitudinal studies may be explained by practice and placebo effects. The MMSE did not exhibit a practice effect and showed the expected decline in scores.

Aged↗
PubMed2002

Statistical heterogeneity in systematic reviews of clinical trials: a critical appraisal of guidelines and practice.

OBJECTIVE: Heterogeneity between study results can be a problem in any systematic review or meta-analysis of clinical trials. Identifying its presence, investigating its cause and correctly accounting for it in analyses all involve difficult decisions for the researcher. Our objectives were: to collate recommendations on the subject of dealing with heterogeneity in systematic reviews of clinical trials; to investigate current practice in addressing heterogeneity in Cochrane reviews; and to compare current practice with recommendations. METHODS: We review guidelines for those undertaking systematic reviews and examine how heterogeneity is addressed in practice in a sample of systematic reviews, and their protocols, from the Cochrane Database of Systematic Reviews. RESULTS: Advice to reviewers is on the whole consistent and sensible. However, examination of a sample of Cochrane protocols and reviews demonstrates that the advice is difficult to follow given the small numbers of studies identified in many systematic reviews, the difficulty of pre-specifying important effect modifiers for subgroup analysis or meta-regression and the unresolved debate concerning fixed versus random effects meta-analyses. There was disagreement between protocols and reviews, often either regarding choice of important potential effect modifiers or due to the review identifying too few studies to perform planned analyses. CONCLUSION: Guidelines that address practical issues are required to reduce the risk of spurious findings from investigations of heterogeneity. This may involve discouraging statistical investigations such as subgroup analyses and meta-regression, rather than simply adopting a cautious approach to their interpretation, unless a large number of studies is available. The notion of a priori specification of potential effect modifiers for a retrospective review of studies is ill-defined, and the appropriateness of using a statistical test for heterogeneity to decide between analysis strategies is suspect.

Clinical Protocols↗
PubMed1997

Hawthorne effect: shortening of fluoroscopy times during radiation measurement studies.

Screening times were recorded before (n = 92, 13 radiologists) and after (n = 75, 6 radiologists) commencing a protocol with dose-area product (DAP) measurements and filling of structured questionnaires. Fluoroscopy times were significantly (p = 0.0001) longer before starting these measurements (median 4.3, mean 5.2 min) than during them (median 3.2, mean 3.6 min), which indicates a Hawthorne effect. Fluoroscopy times did not increase during the DAP measurement period up to 21 barium enemas and a study period of up to 45 days per radiologist. Previous fluoroscopic radiation measurements based on action during an analysis period may be biased towards too short fluoroscopy times and too low doses. Radiation measurement, even if not scientifically indicated, seems a practical way of reducing doses.

Barium Sulfate↗
PubMed2002

Treating fever in children: paracetamol or ibuprofen?

Community health practitioners frequently prescribe or advise parents on antipyretic medications for children with fevers. This mini-review sets out to examine the evidence for the relative effectiveness of two of the most widely available and commonly used over-the-counter medicines - paracetamol and ibuprofen. A systematic literature search was undertaken to identify all studies comparing the effects of the two drugs. The Medline, Embase, Cinahl and RCN databases were searched. Eight randomized controlled trials that reported temperature differences at time-points between 1 and 6 hours after administration were identified. Statistical meta-analysis showed no clear benefit for one drug over another 1 hour after administration. However, by 6 hours after administration ibuprofen was clearly superior resulting in a mean temperature 0.58 degrees C lower than paracetamol. Both drugs appeared well tolerated and no evidence of difference in short-term adverse effects was observed. Both drugs are effective antipyretics but the longer action of ibuprofen may make it preferable in some circumstances.

Acetaminophen↗
PubMed1994

Therapist/patient matching and early treatment dropout.

This study of intake procedures was initiated with a view towards reducing the early dropout rate of substance abusers. Eight different therapists conducted intake interviews of 634 cocaine dependent, first admissions to an outpatient cocaine treatment program. No significant differences in return rate were found across either the eight therapists or their level of academic training. We found that matching therapists and patients with respect to gender and race for the intake interview did not increase the proportion of patients returning for a second visit. In addition, the hypothesis that providing a sense of continuity by having the therapist who conducted the intake interview become the treatment therapist did not result in a higher return rate than if the patient was assigned to a different treatment therapist. Although the results do not indicate methods of further reducing early treatment dropouts they are helpful in reducing concerns about who conducts intake interviews and how patients are assigned.

Adult↗
PubMed2004

Theory of planned behaviour and ecstasy use: an analysis of moderator-interactions.

OBJECTIVE: This study tested potential moderator interactions between components of the Theory of Planned Behaviour (TPB) in relation to ecstasy use, extending previous research. It was expected that attitudes, subjective norms and perceived behavioural control (PBC) would moderate each other in predicting intended use of this drug. METHOD: A cross-sectional survey was administered to 200 young adults. RESULTS: In hierarchical multiple regression analysis, past behaviour and attitude independently predicted intention; previous use of ecstasy and more positive attitudes towards ecstasy use were associated with stronger intentions to use this drug in the future. Moreover, there was a significant interaction between attitude and PBC (R(2)(change) = 0.05). Slope analysis revealed that PBC better predicted intention given more positive attitudes towards ecstasy use. CONCLUSIONS: This moderator function may help explain predictive inconsistencies reported in the literature. Implications for the TPB are considered.

Adaptation, Psychological↗
PubMed2002

Multicomponent procedure to teach conditional discriminations to children with autism.

Five children with autism with a history of failing to acquire conditional discriminations learned to discriminate objects in response to spoken names or to match amounts to numbers with a combined blocking procedure. The procedure for teaching object discriminations involved (a) presenting the same spoken word until 10 consecutive correct responses occurred and (b) keeping the left-right location of the objects on the table constant. After mastery, the requirement for changing the spoken word was gradually reduced. Finally, the spoken words were presented randomly. In the final stage, the objects were located randomly. The procedure to teach number matching was similar. All children learned these discriminations with few errors. This procedure may be beneficial in teaching conditional discriminations to children with learning difficulties.

Autistic Disorder↗
PubMed1998

Personality disorders in sociocultural perspective.

Personality disorders are shaped by a social and cultural context. This principle is supported by evidence that Axis II diagnoses have a different prevalence in different societies, and that some disorders demonstrate cohort effects. Transitions from traditional to modern social structures, accompanied by social disintegration and rapid social change, could account for these phenomena. The main mechanisms of action would involve interference with family functioning and with buffering from the social community.

Cross-Cultural Comparison↗
PubMed2001

Interviewers' and respondents' effects on self-reported alcohol consumption in a Swiss health survey.

OBJECTIVE: Characteristics of interviewers and respondents have been shown to influence the quality of data from survey research in various domains. There is little evidence for such effects in alcohol research, however. The purpose of the study reported here was to examine effects of gender and age of interviewers and respondents simultaneously This was done using hierarchical linear modeling, the advantage of which is that it can account for the clustering effects of respondents being nested within interviewers. METHOD: Data were obtained from the first wave of an ongoing randomized longitudinal study on changes in alcohol consumption in Switzerland. The response rate was 77.9%. Analyses were based on 2,746 (1,749 male) subjects with an average of at least monthly consumption in the 6 months before the telephone interview. Consumption was assessed by means of a graduated frequency measure. Five different hierarchical linear models of increasing complexity were used to test several hypotheses of interviewer and respondent effects. Findings from hierarchical linear modeling were compared with those from "classical" analysis of variance. RESULTS: A theoretical design effect of 1.89 attributable to interviewers was found. Both analyses of variance and hierarchical linear modeling provide support for a structure with a main effect for gender of respondents, as well as a main effect for age of respondents and an interaction effect between interviewers' and respondents' ages. CONCLUSIONS: Interviewer effects affect the estimation of statistics in survey research and must be adjusted for either by means of multilevel analysis or by the use of specialized sample survey software.

Adolescent↗
PubMed2006

The World Health Survey: a report on the field experience in Brazil.

This article reports on the field experience with the World Health Survey in Brazil with the aim of collaborating in the development and enhancement of the methodology and analyzing interview questions based on the interviewers' experience. The authors comment on the field experience and application of the questionnaire, based on reports by regional coordinators and interviewers, in order to shed light on the context in which the interviews took place. The article reports on how the respondents grasped and interpreted the questionnaire. The authors propose improvements in interviewer training and simple interview reporting measures aimed at improved logistics with such nationwide survey instruments.

Brazil↗
PubMed2001

The benefits of interventions for work-related stress.

OBJECTIVES: This quantitative meta-analysis sought to determine the effectiveness of occupational stress-reducing interventions and the populations for which such interventions are most beneficial. METHODS: Forty-eight experimental studies (n = 3736) were included in the analysis. Four intervention types were distinguished: cognitive-behavioral interventions, relaxation techniques, multimodal programs, and organization-focused interventions. RESULTS: A small but significant overall effect was found. A moderate effect was found for cognitive-behavioral interventions and multimodal interventions, and a small effect was found for relaxation techniques. The effect size for organization-focused interventions was nonsignificant. Effects were most pronounced on the following outcome categories: complaints, psychologic resources and responses, and perceived quality of work life. CONCLUSIONS: Stress management interventions are effective. Cognitive-behavioral interventions are more effective than the other intervention types.

Behavior Therapy↗
PubMed2004

Evidence-based public health: moving beyond randomized trials.

Randomized controlled trials (RCTs) are essential for evaluating the efficacy of clinical interventions, where the causal chain between the agent and the outcome is relatively short and simple and where results may be safely extrapolated to other settings. However, causal chains in public health interventions are complex, making RCT results subject to effect modification in different populations. Both the internal and external validity of RCT findings can be greatly enhanced by observational studies using adequacy or plausibility designs. For evaluating large-scale interventions, studies with plausibility designs are often the only feasible option and may provide valid evidence of impact. There is an urgent need to develop evaluation standards and protocols for use in circumstances where RCTs are not appropriate.

Causality↗