[1] Columbia Univ, Coll Phys & Surg, Dept Med, New York, NY 10027 USA
[2] Columbia Univ, Coll Phys & Surg, Dept Neurol, New York, NY USA
[3] Columbia Univ, Mailman Sch Publ Hlth, Dept Biostat, New York, NY USA
[4] Columbia Univ, Mailman Sch Publ Hlth, Dept Epidemiol, New York, NY USA