[1] Univ Sheffield, Sch Med & Populat Hlth, Div Clin Med, Beech Hill Rd, Sheffield S10 2RX, S Yorkshire, England
[2] Univ Sheffield, Sch Med & Populat Hlth, Div Clin Med, Palliat Med, Sheffield, S Yorkshire, England
[3] Univ Nottingham, Sch Hlth Sci, Nottingham, England
[4] Univ Leeds, Div Primary Care Palliat Care & Publ Hlth, Palliat care, Leeds, W Yorkshire, England