[1] Natl Inst Neurosci, Dept Neurol, Singapore 308433, Singapore
[2] Duke NUS Grad Med Sch Singapore, Singapore, Singapore
[3] Natl Univ Hlth Syst, Dept Med, Singapore, Singapore
[4] Univ Pittsburgh, Inst Canc, Div Canc Control & Populat Sci, Pittsburgh, PA USA
[5] Univ Pittsburgh, Grad Sch Publ Hlth, Dept Epidemiol, Pittsburgh, PA USA
[6] Natl Univ Singapore, Saw Swee Hock Sch Publ Hlth, Singapore 117548, Singapore