Primary Care Research Unit of Salamanca (APISAL), Institute of Biomedical Research of Salamanca (IBSAL), Health Service of Castilla y León (SACyL), 37005 Salamanca, Spain. Department of Nursing and Physiotherapy, University of Salamanca, 37007 Salamanca, Spain. University Clinical Hospital of Valladolid, Health Service of Castilla y León (SACyL), 47003 Valladolid, Spain. Health and Social Research Center, University of Castilla-La Mancha, 16071 Cuenca, Spain. Calvià Primary Care Center, Balearic Islands Health Research Institute (IDIBSA), Health Service of Balearic Islands, 07180 Calvià, Spain. Department of Medicine, University of the Balearic Islands, 07122 Palma, Spain. Las Fuentes Norte Health Center, Aragonese Group of Primary Care Research (GAIAP), Aragon Health Research Institute (IISA), Aragon Health Service, 50002 Zaragoza, Spain. Department of Internal Medicine, Psychiatry and Dermatology, University of Zaragoza, 50009 Zaragoza, Spain. Department of Medicine, University of Salamanca, 37007 Salamanca, Spain. Department of Biomedical and Diagnostic Sciences, University of Salamanca, 37007 Salamanca, Spain. EVIDENT Research Group, RICAPPS: Chronicity, Primary Care and Health Promotion Research Network, 37005 Salamanca, Spain.