1. National School of Occupational Medicine, Carlos III Institute of Health, Madrid, Spain.
2. Department of Physical Medicine and Rehabilitation, School of Medicine, Complutense University of Madrid, Madrid, Spain.
3. National Centre of Epidemiology, Carlos III Institute of Health, Madrid, Spain.
4. CIBERNED (Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas), Madrid, Spain.