Project Presentation:
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(1) Alonso J, Angermeyer MC, Bernert S, Bruffaerts R, Brugha.
Sampling and methods of the European Study of the Epidemiology of Mental Disorders (ESEMeD) project.
Acta Psychiatr Scand Suppl. 2004;(420):8-20.
Introduction
The ESEMeD project is a complex population-based home interview survey implemented in six European countries: Belgium, France, Germany, Italy, the Netherlands and Spain.
Sampling methods
- The target population was individuals aged 18 years or older residing in private households in the six study countries.
- A stratified multistage random sample without replacement was drawn in each country. Replacement was prohibited to ensure that every individual had a known probability of selection.
- The sampling frame and the number of sampling stages used to obtain the final sample differed across countries. In each sampling stage, probability sampling methods were implemented (Table 1).
- In four countries (Belgium, France, Italy and Spain), an additional sample of spouses from 10% of the main respondents was randomly selected.
- A random selection of individuals that had been either difficult to reach or were committed refusals was reapproached to attempt a refusal conversion in order to maximize response rate. The interviews obtained from this approach have been weighted by the inverse of their probability of selection.
- The overall response rate of the study was 61.2%. Within countries rates ranged from 45.9% in France to 78.6% in Spain.
- Different types of weights were applied to the sample data to produce estimates of statistics that would have been obtained if the entire sampling-frame had been surveyed.
The survey questionnaire
The questionnaire includes a revised version of the Composite International Diagnostic Interview (WMH-CIDI) together with specific information on severity of the disorders, symptoms, disability and quality of life, use of services, use of medication and risk factors. It is structured in 38 different sections Tabla 2.
The Composite International Diagnostic Interview (CIDI)
- The Composite International Diagnostic Interview (CIDI) is a comprehensive, fully structured diagnostic interview for the assessment of mental disorders.
- By means of computerized algorithms it provides lifetime and current (12- month and 1-month previous to the interview) diagnoses according to the International Classification of Diseases (ICD-10) , and the Diagnostic and Statistical Manual for Mental Disorders (DSM-IV) .
- For the ESEMeD study, a revised and further enhanced version of the CIDI (WMH-CIDI) was developed and adapted by the Coordinating Committee of the WHO-WMH 2000 Initiative. The WMH-CIDI includes fully structured questions on presence, persistence and intensity of clusters of psychiatric symptoms followed by probes for age of onset and lifetime course.
- The WMH-CIDI was first produced in English and underwent a rigorous process of adaptation in order to obtain conceptually and cross-culturally comparable versions in each of the target countries and languages.
Other study variables included in the survey interview
- The survey interview incorporated measures of severity of depression and anxiety disorders based on modifications of standardized instruments.
- It also included questions about family burden, and specific questions that assessed dimensions of disability and health-related quality of life (i.e WHODAS-II).
- Information on risk factors included family history, stressful emotional experiences, life events, childhood disorders, personality, spouse relationship, sexual life, religion, age, gender, ethnicity and social class.
- A battery of questions regarding the use of services was also administered. Items address whether respondents consulted a health professional for specific emotional problems, comorbid conditions and general health. It was also assessed the reasons for using health services, whether the respondents received treatment, the type of treatment, the duration and intensity of care, and barriers to care.
Questionnaire itineraries
- Two main questionnaire itineraries were defined: the long and the short path.
A lifetime psychiatric instrument containing screening questions for some specific disorders of mood and anxiety was administered to all respondents at the beginning of the questionarie. Individuals that, based on their anxiety or depression symptoms, could be considered as high risk individuals, and a random subsample (25%) of the respondents without symptoms (low risk individuals) followed the long path. The remaining 75% of respondents without symptoms not randomly selected for the long path followed the short path of the questionnaire.
Survey procedures and data control
- A survey firm in each country was contracted to undertake the survey fieldwork. Each survey firm provided a detailed description of the work to ensure standardization between countries.
- Questions were administered by trained lay interviewers using a computer-assisted personal interview (CAPI) that was programmed centrally with the Blaise software system.
- All interviewers had received the same training and were expected to adhere to the same protocol regarding contacts and interview administration. In addition, a pretest phase was carried out in each country participating in the project.
- The interview took place in the respondent’s home. Eligible individuals were asked for their informed consent to participate in a face-to-face interview.
- Once completed, the interviews were sent to the central project Data Center (Institut Municipal d’Investigació Médica (IMIM), Barcelona, Spain) for checking and storage.
- Data were managed and stored using Microsoft SQL Server 2000 software.
- Data quality was controlled in a number of ways to ensure that the study yielded information with the highest reliability, validity and timeliness. The control procedures were organized locally and centrally, and were coordinated by IMIM staff and members of the ESEMeD Scientific Committee.
Clinical reappraisal
- After the main CIDI interview, a clinical reappraisal study was carried out in three of the six countries: France, Italy and Spain.
- The aim was to compare the CIDI diagnoses obtained by the lay interviewer with those obtained by the reappraisal clinician administering the axis I Structured Clinical Interview for DSM-IV (SCID), a semi-structured interview that is reliable in community surveys.
- Clinical severity scales were incorporated into the SCID and were interleaved within the modules to ease administration. Global assessment of functioning (GAF) scale, was also rated by the clinicians.
- A total of 264 clinical reappraisal interviews were performed.
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Analysis of the data
- Three data analysis centres were involved in the project: IMIM (Barcelona, Spain), GlaxoSmithKline (GSK) (Philadelphia, USA; London, UK) and Harvard University (Boston, USA).
- The investigators requested analyses according to the publications plan and using a standard template form.
- Crosschecking of results was performed at a prefinal stage. To do so, the last version of analysis tables together with the programing information used to generate the tables were shared among the analysis teams.
- Results were provided to all the project Scientific Committee members for review.
- All the analyses were performed using SASTM software, version 8 of the SAS System for Windows and SUDAAN.
TABLE 1
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