Elsevier

Public Health

Volume 118, Issue 6, September 2004, Pages 426-433
Public Health

Methods and demographic findings of the baseline survey of the NEDICES cohort: a door-to-door survey of neurological disorders in three communities from Central Spain

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Abstract

Objective: To describe the methods and general results of the baseline longitudinal survey in a defined cohort of elderly people from three areas of Central Spain (urban and rural). The survey was designed to study dementia, essential tremor, Parkinson's disease and stroke.

Study design: A population-based longitudinal study with door-to-door interviews.

Methods: This study was carried out in two phases: Phase 1 (health status questionnaire and screening performed by lay interviewers) and Phase 2 (diagnosis of neurological illnesses by neurologists).

Results: The study flow chart, screening instruments for neurological disorders, main demographic data (age, sex, educational attainment, occupation) and general health status of the 5278 screened participants (2238 men and 3040 women) are given for the two phases. The response rate was 85.3%, and participation was higher in men and in the urban area.

Conclusions: Participation rates were good in both phases of the NEDICES baseline study, and this was influenced by age, sex and setting of the participants. Educational attainment, occupation and health status data are analogous to other Spanish studies performed in the elderly. As the study population was large and good participation rates were achieved, precise analysis of morbidity of the neurological disorders investigated will be possible.

Introduction

Several population-based studies investigating neurological disorders in the elderly have been performed recently in Spain.1., 2., 3., 4., 5., 6., 7., 8., 9. However, these studies had relatively small population samples (less than 1500 people) and they evaluated single-site populations. Between 1994 and 1995, a large-scale survey was performed to obtain an elderly Spanish cohort, in whom health status will be estimated, in addition to morbidity (prevalence and incidence rates) and mortality rates of age-related cardiovascular and neurological diseases.

The NEDICES cohort was carried out in two phases (screening and diagnosis) according to the rules of a population-based survey in rare diseases, in which specialists are required to make differential diagnoses in a large sample.10

The NEDICES study was based on two previous projects: the World Health Organization Age-Associated Dementia project (WHO-AAD)11 and the EPICARDIAN study.12 Other aspects were included for assessing caregivers' needs. Spanish participation in the WHO-AAD project was mainly for the validation of dementia screening tests. The EPICARDIAN study was designed to investigate cardiovascular diseases and their risk factors. The NEDICES study selected three geographical areas to obtain a cohort of elderly people dwelling in one well-defined area of Spain (Central Spain), but with different cultural and socio-economic backgrounds. The main aim of this longitudinal project was to analyse the prevalence and incidence rates of neurological diseases (stroke and transient ischaemic attack syndrome (TIA), dementia, Parkinson's disease (PD) and essential tremor) over a 3-year period.

In this paper, we describe the planning and methods of this large-scale survey, and report the demographic findings of the NEDICES cohort.

Section snippets

Geographical areas

Three communities of central Spain were studied, two urban and one rural. The first urban site was the district of ‘Margaritas’ in Getafe (170,000 inhabitants, 15.5% over 65 years of age), a suburb of metropolitan Madrid composed mainly of working-class people. The second urban site was the ‘Lista’ area in a central district of Madrid (approximately 150,000 inhabitants, 16.5% over 65 years of age), composed mainly of people of medium or medium-high income (professionals and white-collar

Results

Fig. 1 shows the flow chart of the survey according to its phases. From 6395 people on the census, only 5914 subjects were eligible for the study (deaths before the onset of the study, 115; census errors, 58; changed address, 308; total not eligible=481 persons). Of these 5914 eligible subjects, 636 were not screened (deaths before the onset of Phase 1, 52; refusals, 292; unreachable, 292), 4503 were screened directly and 775 were screened indirectly for several reasons (deaths during screening

Discussion

The aim of this study was to establish a specific Spanish cohort of elderly people dwelling in three communities of central Spain, and to estimate incidence data and risk factors of several neurological disorders (dementia, PD and essential tremor, and stroke and TIA) over 3 years. For this purpose, we focused on three geographical areas with different cultural and sociodemographic characteristics. According to the results on education and occupation, this survey offered three cohorts with

Acknowledgements

The NEDICES study was supported through grants from the World Health Organization Age-Associated Dementia Project (WHO-AAD), the EPICARDIAN study, PB1225-C04 and ASTA Medica (videotaping of Parkinsonian patients), and official Spanish Research Agencies (FIS 93/0773, CAM 94/0032).

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