Reflections on the preliminary results of the ELES Longitudinal study

The Longitudinal Study "Ageing in Spain" (ELES) aims to follow, for 20 years, Spaniards born before 1960 in order to analyse their ageing process through the collection of periodic information. To find out the feasibility of this proposal, it was decided to carry out a large pilot study in 2011, in which information was collected through questionnaires from 1,747 people from all over Spain. Objective measurements of the body and physical and cognitive function were also carried out and blood was drawn. Most of the variables are made available to the research community free of charge on the project's website (www.proyectoeles.es). We hope to obtain follow-up data in 2015

This page also contains the first articles that have been published based on this information, specifically on quality of life, participation in the study and the influence of socio-educational variables on cognitive functioning.

As one of the researchers who has had the opportunity to follow more closely the collection, purification and dissemination of the data, the three fundamental lessons I have drawn from this process are

1) The scientific and organisational level of our country makes it possible to tackle a project of these dimensions, and undoubtedly greater ones, with a guarantee of success. What we lack is not capacity, but the conviction in the general society and also in the research community that it is worth spending resources on a national longitudinal study on ageing.

2) The criteria for selecting study participants should seek not so much geographical representativeness as a guarantee of participation and follow-up. The pilot study was designed to interview people selected at random from many municipalities in all the autonomous communities. But it has become clear that many Spaniards are tired of participating in surveys, even if these are endorsed by prestigious public and research bodies. The non-participation of selected people is especially serious when those who participate are different from those who do not. We have seen in the pilot study that participation depends on the socio-economic level and the region of residence. It is also possible that many of the participants may lose interest in the study and we may not be able to follow them, which is especially negative in a longitudinal project. In order to achieve a good participation and adherence to the study I think it is essential to first convince the communities where the individuals are to be selected of the importance of the project. The effort that this requires is not compatible with extending the recruitment of participants throughout Spain. We will have to look for alternatives, worse from the point of view of design, but in which a high level of participation of those selected is guaranteed.

3) When I asked for advice on the selection of questions in the questionnaire, María Victoria Zunzunegui, one of the first researchers to carry out a longitudinal study on ageing in a Spanish population (Leganés), recommended that I only put questions that someone had committed to analyse. To try to ensure that most of the euros spent on obtaining the information have been spent in a useful way, there has to be a highly motivated and large group of researchers waiting "anxiously" to be able to analyse it. Researchers who have to master the areas they ask questions about.  We hope that the use of the data from the pilot study of the website by the research community will generate a critical mass of researchers that will bring the longitudinal study to fruition.

KeywordsProject information: proyectoeles.es