1. Robarts Research Institute (R.A.H., H.C.), London, Canada N6A 5K8;
2. Center for Studies in Family Medicine (S.B.H.), University of Western Ontario, London, Canada N6A 5K8;
3. Samuel Lunenfeld Research Institute and Department of Medicine, Mount Sinai Hospital, University of Toronto (A.J.G.H., B.Z.), Toronto, Ontario, Canada M5B 1X5