1. From the Departments of Pediatrics (R.L.S., S.P.M.) and Healthcare and Epidemiology (R.L.S.), University of British Columbia, Vancouver, British Columbia, Canada; The Centre for Applied Health Research and Evaluation (R.L.S.), Vancouver, British Columbia, Canada; and the Departments of Pediatrics and Neurology (P.S.M., S.P.M.), University of California, San Francisco, Calif.