Biomedical subjects

Jürgen Hoyer

Publications and source records attributed to Jürgen Hoyer.

4 recordsLinked to original sources

PubMed2003

Association chain graphs: modelling etiological pathways.

Multiple time-dynamic and interrelated risk factors are usually involved in the complex etiology of disorders. This paper presents a strategy to explore and display visually the relative importance of different association pathways for the onset of disorder over time. The approach is based on graphical chain models, a tool that is powerful but still under-utilized in most fields. Usually, the results of these models are displayed using directed acyclic graphs (DAGs). These draw an edge between a pair of variables whenever the assumption of conditional independence given variables on an earlier or equal temporal footing is violated to a statistically significant extent. In the present paper, the graphs are modified in that confidence intervals for the strengths of associations (statistical main effects) are visualized. These new graphs are called association chain graphs (ACGs). Statistical interactions cause 'edges' between the respective variables within the DAG framework (because the assumption of conditional independence is violated). In contrast they are represented as separate graphs within the subsample where the different association chains may work within the ACG framework. With this new type of graph, more specific information can be displayed whenever the data are essentially described only with statistical main- and two-way interaction effects.

Alcoholism↗

PubMed2002

Screening for anxiety in an epidemiological sample: predictive accuracy of questionnaires.

The study examined the predictive accuracy of selected questionnaires when screening for anxiety in a representative epidemiological sample of young female adults (N = 1877). All participants were diagnosed using a structured diagnostic interview. Anxiety questionnaires included global as well as specific measures (Beck Anxiety Inventory (BAI), Symptom Checklist, Anxiety Sensitivity Index (ASI), Fear Questionnaire (FQ), Mobility Inventory (MI)). Sensitivity, specificity, positive and negative predictive power were computed for two screening decisions: (1) identifying any anxiety disorder or (2) identifying a specific anxiety disorder (agoraphobia) within the total sample and the clinical subsample. Due to naturalistic (low) base rates in epidemiological samples, diagnostic indices were lower than those previously reported. However, questionnaire data proved useful when a specific disorder was targeted (agoraphobia) and specific symptoms were operationalized.

Adolescent↗

PubMed2002

Generalized anxiety and depression in primary care: prevalence, recognition, and management.

AIMS: Determine attitudes toward patients with generalized anxiety disorder (GAD) and major depressive episodes (MDE) in primary care; determine prevalence of GAD, MDE, and comorbid GAD/MDE among primary care patients; assess physician recognition of GAD and MDE; and describe primary care interventions for these patients. METHOD: 558 primary care physicians participated in a 1-day survey. Over 20,000 patients completed a diagnostic-screening questionnaire for GAD and MDE. Physician questionnaires included a standardized clinical appraisal of somatic and psychosocial symptoms and information on past and current treatments and a prestudy questionnaire assessing experience with and attitudes toward patients with GAD and MDE. RESULTS: 56.9% of physicians viewed GAD as a genuine mental disorder with clinical management problems and considerable patient burden; 27.4% treated GAD patients differently from MDE patients. 5.3% of patients met criteria for GAD, 6.0% for MDE, 3.8% for pure GAD, 4.4% for pure MDE, and 1.6% for comorbid GAD/MDE. Pure GAD and MDE were associated with disability, high utilization of health care resources, and suicidality, which were even higher with comorbid GAD/MDE. Physicians recognized clinically significant emotional problems in 72.5% of patients with pure GAD, 76.5% with pure MDE, and 85.4% with comorbid GAD/MDE. However, correct diagnosis was much lower (64.3% for MDE and 34.4% for GAD). Although the majority of patients with recognized GAD or MDE were treated, only a small minority with GAD were prescribed medications or referred to specialists. CONCLUSION: The high proportion of respondents with pure GAD is inconsistent with previous reports that GAD is usually comorbid with depression. GAD remains poorly recognized and inadequately treated. Improving the recognition and treatment of GAD in primary care patients is discussed relative to new treatments.

Adolescent↗

PubMedDate not supplied

[What to do if statistical power is low? A practical strategy for pre-post-designs].

This article deals with the issue of statistical validity when evaluating interventions. The most common study design with two groups and two points of measurement is discussed. In clinical research settings, unsatisfactory statistical validity is often seen due to small sample sizes. In order to resolve this problem, a strategy based on an approach by Hager is proposed which takes both significance testing and effects sizes systematically into account. Using an example from clinical research practice the problematic issue of statistical power is introduced and methods to increase the power of tests are discussed. Within this framework, Erdfelder's compromise power analysis (computing alpha levels according to a predetermined beta/alpha error ratio) is crucial as well as a lowering of the number of applied tests by data reduction and the improved detection of potential effects by methods to reduce error variance. The results show that significance tests should not be used in case of small sample and effect sizes. In these cases different approaches should be used.

Data Interpretation, Statistical↗