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Results for “Effect Modifier, Epidemiologic”

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At least 163 records · Page 9Linked to original sources
PubMed1991

Theory-based screening for prevention: focusing on mediating processes in children of divorce.

Prevention programs in mental health theoretically can benefit from selecting participants who have a greater likelihood of developing psychological problems because of their exposure to the putative mediators targeted for change in an intervention. Screening on mediators may increase statistical power to detect program effects, enhance the cost-effectiveness of intervention trials, and decrease the possibility of iatrogenic effects. The circumstances that optimize the strategy of screening on the basis of mediating variables are discussed, and data are presented to illustrate the development of a mediational selection strategy to identify families who might best benefit from a preventive intervention for children of divorce. In addition, we present evidence that adjustment problems for children experiencing a divorce, as with most mental health problems, are not the result of one specific factor, but are jointly determined by several mediating processes that occur subsequent to the divorce. The mediational selection strategy developed illustrates the utility of measuring a set of mediational processes central to conferring risk for mental health problems to children of divorce.

Adolescent↗
PubMed1993

Charting the process of change: a primer on survival analysis.

Survival analysis is a powerful and useful technique for understanding qualitative change. This article provides a practical, nontechnical introduction to the use of survival analysis for social scientists. Important issues in using survival analysis are discussed, including research design, data preparation and management, and data analysis. Attendance data from a self-help organization are used to illustrate common survival analysis tasks such as describing the overall survival and hazard functions, examining covariate effects, and modeling the form of the hazard function over time. An appendix that discusses the strengths and weaknesses of current survival analysis computer programs is included.

Data Collection↗
PubMed1994

Effects of repeated questionnaire administration in longitudinal studies of adolescent males' sexual behavior.

By comparing four similar groups of young adolescent males who completed questionnaires about their sexual behavior different numbers of times at various intervals, we explore the hypothesis that repeated questionnaire completion will affect sexual behavior. We find little support for the hypothesis even when the number of questionnaire administrations is very high.

Adolescent↗
PubMed1994

When to measure resting values in studies of children's cardiovascular reactivity.

Investigations suggesting that the order of obtaining resting and cardiovascular reactivity measurements moderates values have provided inconsistent results and have not analyzed data from children; the generalizability of results is uncertain. In this investigation, all children enrolled in the eighth-grade classrooms of the public schools of an entire county (n = 451) participated in standardized reactivity assessments. The order of resting and reactivity measurements was randomized by examination day (a total of 19 days). Analyses indicated that all comparisons of order effects on mean resting blood pressure and heart rate, as well as reactivity (both change from resting and absolute values and both mean and maximal values), were nonsignificant. Results indicate that measurement order is not always a necessary consideration in studies of reactivity; the conditions under which measurement order is a consideration requires clarification.

Adolescent↗
PubMed1994

Testing strategies to increase use of chloroquine chemoprophylaxis during pregnancy in Malaŵi.

The widespread problem of low and non-compliance to antimalarial chemoprophylaxis during pregnancy demands that attention be focused on alternative approaches to programming, product acceptability and demand for preventive services. This study describes the testing of three interventions to determine their effect on use of chloroquine (currently the most widely used drug for chemoprophylaxis) during pregnancy. The strategies evolved from community-based formative research undertaken to learn about the local concept of malaria and issues surrounding malaria prevention and treatment during pregnancy. The resulting interventions were tested in four clinics, and included a change in the health education message given during antenatal sessions, distribution of a sugar-coated chloroquine tablet, and an intervention combining the two strategies. The results showed a 45% increase in chloroquine use when the health education message was changed, and a 64% increase when the product was changed. High use levels were maintained with the combined intervention; an additive effect was seen. The study shows that improving the product was the most important factor in increasing the use of the program, and that changing the health education message can also make an impact on use.

Chemistry, Pharmaceutical↗
PubMed1993

Electromyographic biofeedback for neuromuscular reeducation in the hemiplegic stroke patient: a meta-analysis.

The efficacy of electromyographic biofeedback (EMG-BF) for neuromuscular reeducation in the stroke patient has been difficult to establish. The purpose of this study was to assess EMG-BF efficacy through meta-analysis. We searched the English-language clinical studies of biofeedback, stroke, and cerebral vascular disease between 1966 and 1991 using MEDLINE, PsycINFO, REHABDATA, and Dissertation Abstracts International. Studies were included in the analysis if (1) the patients sustained a cerebral vascular accident that resulted in hemiplegia, (2) the study had a randomized or matched control group, (3) the study measured a functional outcome, and (4) EMG-BF was the independent variable. Eight studies met the inclusion criteria (n = 192). Their average effect size was 0.81. The 95% confidence interval for the effect size was 0.5 to 1.12. These results indicate that EMG-BF is an effective tool for neuromuscular reeducation in the hemiplegic stroke patient.

Activities of Daily Living↗
PubMed1994

The outcome problem in psychotherapy: what have we learned?

The outcome problem in psychotherapy has usually been studied without much regard to the theories underlying the methods used. It is suggested that theories are vital to scientific advancement, and that without them we cannot even specify criteria to judge outcomes. Numerous studies since the 1950s have in essence failed to disconfirm the view that various forms of psychotherapy do not show greater effectiveness than spontaneous remission or placebo treatment. An effort is made to clarify the nature of spontaneous remission and placebo treatment, and to discuss the consequences of the many empirical findings and meta-analyses published over the past 50 years. A theory is suggested linking spontaneous remission, placebo treatment, psychotherapy and behaviour therapy, leading to a discussion of ethical considerations and cost-effectiveness issues.

Cost-Benefit Analysis↗
PubMedDate not supplied

Evaluation of research studies. Part III: Statistical significance testing.

Reading and interpreting research studies is an important and necessary activity of clinical practitioners. Correct evaluation of research findings requires appreciation of certain fundamentals of research methodology and statistics. This article, the third of the series, will review issues pertinent to statistical significance testing.

Bias↗
PubMed1991

Planning the analysis of a breast cancer prevention trial.

The analysis of cancer prevention trials necessitates specialized procedures. Differences in the analysis plan between cancer prevention and therapy trials are emphasized. Discussion is focused upon (a) how trial conduct influences the analysis, (b) how noncompliance affects the analysis and the considerations this raises during the design and conduct of the trial, (c) how delays in the effect of the intervention impinges upon the analysis, and (d) statistical methods available to carry out the analysis. The analysis of a cancer prevention trial represents a final step in the evaluation of the study intervention and requires an adaptive planning procedure.

Breast Neoplasms↗
PubMed1989

Practical problems in interim analyses, with particular regard to estimation.

This article considers some of the practical problems inherent in interim analyses and stopping rules for randomized clinical trials. Topics covered include group sequential designs, trials with unplanned interim analyses, estimation problems in clinical trials with planned interim analyses, and the balance between individual and collective ethics. Particular attention is paid to the fact that clinical trials that stop early are prone to exaggerate the magnitude of treatment effect. Accordingly, a Bayesian "shrinkage" method of analysis is proposed to help quantify the extent to which surprisingly large point and interval estimates of treatment difference in clinical trials that stop early should be moderated.

Bayes Theorem↗
PubMed1991

Out of sight, out of mind--2. Social and historical contexts of self-harmful behaviour among aborigines of remote Australia.

Statements regarding the absence of suicidal and other self-harmful behaviour among Australian Aborigines are now untenable. The preceding paper presented the wider context of suicides in custody by examining suicide and other self-harmful behaviour in the Aboriginal population of the Kimbereley region of Western Australia. The emergence of suicide in that population was further located within an increase in deaths from non-natural causes over the last two decades. Following a brief history of the region, this paper develops an even wider context--suicidal behaviour among indigenous groups elsewhere. The relevance of these findings to the trends among Kimberely Aborigines is explored, leading to the central theme of the paper, the importance of an understanding of the socio-historical context in evaluating emerging patterns of harmful behaviour, and their relationship to alcohol use. Results obtained during a survey of the patterns and consequences of alcohol use from a stratified random sample of 516 Kimbereley Aborigines are presented. The author concludes by using the behaviours described in this and the preceding paper to examine the way in which Aboriginal 'problems' are constructed by the wider society, and 'solutions' defined.

Alcoholism↗
PubMed1994

The use of depth interviewing with vulnerable subjects: lessons from a research study of parents with learning difficulties.

This paper explores the practicalities of using the technique of depth interviewing with people who have learning difficulties. The authors set out to provide other researchers with guidance in the use of the life story approach and to demonstrate its utility with this vulnerable and devalued group of informants. They conclude that depth interviewing can provide new knowledge not accessible through other methods of data collection, and offers a way of giving people with learning difficulties a voice in the making of their own history.

Confidentiality↗
PubMed1995

Clinical and public health perspectives and applications of health-related quality of life measurement.

Health-related quality of life (HRQL) measures have been developed from the utilitarian ethical perspective of public health medicine which may be contrasted with individual-centered indicators; these emphasise the unique experience of a patient. The impairment-disability-handicap framework provides a more complete description of disease consequences and health outcomes than a generic HRQL indicator. The assessment of reliability and validity of HRQL indicators is often carried out inappropriately: population repeatability is measured when an indicator will be used to examine changes in individuals; between observer variation may be large compared with variation between populations. Content and construct validity are usually measured but the more important predictive validity is neglected. Effect sizes of HRQL indicators are likely to be inflated by use of between subject estimates of variance but the more appropriate within subject variance is seldom reported. HRQL indicators are of very limited value for many clinical and public health tasks: monitoring health of individuals and populations; evaluating the effects of health and social policy; allocating resources; evaluating the effects of treatment. Alternative methods of assessment derived from the impairment-disability-handicap conceptual framework are preferable.

Effect Modifier, Epidemiologic↗
PubMed1992

Reporting the size of effects in research studies to facilitate assessment of practical or clinical significance.

"Statistically significant" results may lack practical or clinical significance, and the description of results in reports of research studies is frequently incomplete or misleading in presentation of data necessary to assess such significance (effect sizes). Various common presentations are discussed, and one method of presentation of results is proposed that not only encompasses all the others, but enhances the scope of useful information conveyed in a research report. The results of the Infant Health and Development Program (IHDP) are used to illustrate the method.

Child Behavior↗
PubMedDate not supplied

Interviewer effects on self-reported substance use among homeless persons.

This study examines respondent editing of survey responses to questions regarding substance use. Previous research has identified several types of interviewer effects that may be associated with respondent editing, including direct and social distance effects. Little is known, however, regarding how these potential effects may influence self-reported substance use behavior. Data analyzed for this study were collected as part of a survey of substance use among homeless persons conducted in Cook County, Illinois. A total of 481 respondents were sampled at random in emergency and transitional shelters, soup kitchens, drop-in centers, and single room occupancy (SRO) hotels. Overall, a direct, gender-based effect was observed, with homeless respondents of both genders more willing to reveal substance use behaviors to male interviewers. Some race- and age-related direct effects were also identified, with White and older interviewers obtaining more reports of substance use. These findings yield important evidence regarding respondent editing of self-reported substance use and have implications for the common practice of demographically matching interviewers and respondents.

Adolescent↗
PubMed1993

Effects of adjacent surfaces of different shapes on regurgitant jet sizes: an in vitro study using color Doppler imaging and laser-illuminated dye visualization.

OBJECTIVES: The present study was designed to estimate the influence of different-shaped adjacent surfaces on regurgitant jets as assessed by color Doppler imaging and laser-illuminated dye optical visualization. BACKGROUND: Because color Doppler techniques provide real-time two-dimensional imaging of flow, the evaluation of valvular regurgitation by analysis of variance-encoded regurgitant jets by this method has been widely used in clinical studies. However, recent studies have demonstrated that color Doppler jet sizes are affected not only by several hemodynamic factors and instrument settings but also by the interaction between jets and adjacent wall surfaces. In clinical conditions, jets may interact with adjacent walls of variable shapes that might have different effects on the jet size. METHODS: An in vitro model was constructed consisting of a rigid, optically clear receiving chamber that had no outlet resistance and had a pulsatile pump ejecting through 1.5, 2.3 and 3.1 mm2 inflow orifices into the chamber. The surfaces were flat or smoothly and equally curved, convex and concave aluminum positioned at 0, 2 and 4 mm from and to the side of the inflow orifices. The pump was run with stroke volumes from 0.5 to 3.0 ml and with a pulse frequency of 70 beats/min. The echocardiographic and laser beams were aimed at the inflow orifice imaging jets perpendicular to the surfaces (vertical view) through the central plane of the jet flows. Maximal jet areas were measured by both color Doppler techniques and laser-illuminated dye visualization. RESULTS: Color Doppler study showed fair correlation between the jet areas and the stroke volumes (r = 0.83 to 0.99), but the jet sizes under different surface conditions were variable. All the surface jet areas at a jet-surface distance of 0 and 2 mm were smaller than free jet areas at the same stroke volume for both flat and convex surfaces (p < 0.001). Flow constraint by the concave surface resulted in the smallest jet areas (p < 0.001). The color Doppler jet areas on the curved surfaces were significantly smaller than the laser-illuminated dye visualization jet areas (p < 0.01 to 0.0001). However, at intermediate jet-surface distances (4 mm and sometimes 2 mm with higher velocity flows), jet interaction with the flat and especially with the convex surface resulted in larger jets. This effect was most pronounced on dye fluorescence studies because flow around these jets consisted mainly of low velocity vortical events with only partial surface adherence and these low velocity swirling flows were not well imaged by color Doppler technique. CONCLUSIONS: Our study suggests that the different-shaped adjacent surfaces with different degrees of flow alterations resulted in variable decreases in jet size and that color Doppler imaging could not encode and image the angled and low velocity swirling events well when jets flowed along the curved surfaces. These effects need to be taken into account when interpreting color Doppler images.

Analysis of Variance↗