1 Department of Health Sciences, University of Oslo, Pb 1089 Blindern, 0317 Oslo, Norway; Norwegian National Advisory Unit on Ageing and Health, Vestfold Hospital Trust, Pb 2136, 3103 Tønsberg, Norway; Department of Geriatric Medicine, Oslo University Hospital, Pb 4956 Nydalen, 0424 Oslo, Norway. Electronic address: g.g.tangen@medisin.uio.no.
2 Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, Pb 4 St. Olavs Plass, 0130 Oslo, Norway. Electronic address: astrid.bergland@hioa.no.
3 Norwegian National Advisory Unit on Ageing and Health, Vestfold Hospital Trust, Pb 2136, 3103 Tønsberg, Norway; Department of Geriatric Medicine, Oslo University Hospital, Pb 4956 Nydalen, 0424 Oslo, Norway. Electronic address: knut.engedal@aldringoghelse.no.
4 Department of Health Sciences, University of Oslo, Pb 1089 Blindern, 0317 Oslo, Norway. Electronic address: a.m.mengshoel@medisin.uio.no.