A nested case-control study Mahyar Etminan, PharmD, Ali Samii, MD and James M. Brophy, MD, PhD, FRCPC From the Center for Clinical Epidemiology and Evaluation (M.E.), Vancouver Coastal Health Research Institute, Canada; Department of Medicine (M.E.), University of British Columbia, Vancouver, Canada; Department of Neurology (A.S.), University of Washington, Seattle, WA; and Department of Medicine