[1] G Gennimatas Gen Hosp, Dept Internal Med, Thessaloniki 54635, Greece
[2] Univ Southampton, Southampton Gen Hosp, MRC Lifecourse Epidemiol Unit, Southampton, Hants, England
[3] Univ Athens, Sch Med, Dept Crit Care, Attikon Univ Hosp, GR-11527 Athens, Greece
[4] Univ Athens, Sch Med, Dept Internal Med, Attikon Univ Hosp, GR-11527 Athens, Greece