[1] Imperial Coll London, Sch Publ Hlth, Dept Primary Care & Publ Hlth, St Dunstans Rd, London W6 8RP, England
[2] Univ Naples Federico II, Dept Publ Hlth, Naples, Italy
[3] Univ Manitoba, Max Rady Coll Med, Rady Fac Hlth Sci, Dept Med, Winnipeg, MB, Canada
[4] Univ Manitoba, Max Rady Coll Med, Rady Fac Hlth Sci, Dept Community Hlth Sci, Winnipeg, MB, Canada
[5] UCL, Fac Brain Sci, Queen Sq Inst Neurol, Queen Sq Multiple Sclerosis Ctr,Dept Neuroinflamm, London, England
[6] Univ Coll London Hosp, Biomed Res Ctr, Natl Inst Hlth Res, London, England