“…As far as the language is concerned, 18 studies were in English (7,(20)(21)(22)(23)(24)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37) and one in Spanish (25) . According to the country of publication, nine studies were carried out in North America (7,20,(24)(25)31,(33)(34)(36)(37) ; In Europe, seven (21)(22)(23)(26)(27)(28)32) and in Asia and Australia, three (29)(30)35) . As for the publication period, 14 different journals were identified, most notably the Archives of Gerontology and Geriatrics, with three publications (26)(27)32) , and Archives of Internal Medicine (31,37) , BMC Geriatrics (23,28) and Journal of Gerontology (7,33) , with two studies each, and the others, one article …”