[1] Univ Nottingham, Div Epidemiol, Community Hlth Sci Sch, Queens Med Ctr, Nottingham NG7 2RD, England
[2] Assiut Univ, Community Hlth Sch, Fac Med, Assiut, Egypt
[3] Univ S Australia, Ctr Intergenerat Hlth Res, Div Hlth Sci, Social Epidemiol Unit, Adelaide, SA 5001, Australia
[4] Univ Nottingham, Div Psychiat, Community Hlth Sci Sch, Queens Med Ctr, Nottingham NG7 2RD, England