Dependency evolution in Spanish disabled population : a functional data analysis approach

In a health context dependency is defined as lack of autonomy in performing basic activities of daily living that require the care of another person or significant help. However, this contingency, if present, changes throughout the lifetime. In fact, empirical evidence shows that, once this situation occurs, it is almost impossible to return to the previous state and in most cases the intensity increases. In this article, the evolution of the intensity in this situation is studied for the Spanish population affected by this contingency. Evolution in dependency can be seen as sparsely observed functional data, where for each individual we get a curve only observed at those points in which changes in the condition of his/her dependency occur. We use functional data analysis techniques such as curve registration, functional data depth or distance-based clustering to analyse this kind of data. This approach proves to be useful in this context since it takes into account the dynamics of the dependency process and provides more meaningful conclusions than simple pointwise or multivariate analysis. The database analysed comes from the Survey about Disabilities, Personal Autonomy and Dependency Situations, EDAD 2008, (Spanish National Institute of Statistics, 2008). The evaluation of the dependency situation for each person is ruled in Spain by the Royal Decree 504/2007 that passes the scale for assessment of the situation set by Act 39/2006. In this article, the scale value for each individual included in EDAD 2008 has been calculated according to this legislation. Differences between sex, ages and first appearance time have been considered and prediction of future evolution of dependency is obtained