[1] Karolinska Inst, Inst Environm Med, Div Epidemiol, SE-17177 Stockholm, Sweden
[2] Univ Alberta, Sch Publ Hlth, Dept Publ Hlth Sci, Edmonton, AB T6G 2M7, Canada
[3] Univ Alberta, Sch Publ Hlth, Alberta Ctr Injury Control & Res, Edmonton, AB T6G 2M7, Canada
[4] Toronto Western Hosp, Univ Hlth Network Rehabil Solut, CREIDO, Toronto, ON M5T 2S8, Canada
[5] Toronto Western Res Inst, Div Hlth Care & Outcomes Res, Toronto, ON, Canada
[6] Univ Toronto, Dept Publ Hlth Sci, Toronto, ON M5S 1A1, Canada
[7] Univ Toronto, Dept Hlth Policy Management & Evaluat, Toronto, ON M5S 1A1, Canada
[8] Inst Work & Hlth, Toronto, ON, Canada
[9] Univ British Columbia, Dept Med, Vancouver, BC V5Z 1M9, Canada
[10] Merck & Co Inc, Endocrinol Analgesia & Inflammat, Rahway, NJ 07065 USA
[11] NYU, Sch Med, Dept Orthopaed, New York, NY USA
[12] NYU, Sch Med, Dept Environm Med, New York, NY USA
[13] NYU, Sch Med, Program Ergon & Biomech, New York, NY USA
[14] NYU, Grad Sch Arts & Sci, New York, NY USA
[15] NYU, Med Ctr, OIOC, New York, NY 10016 USA
[16] Univ Hawaii Manoa, Dept Publ Hlth Sci, John A Burns Sch Med, Honolulu, HI 96822 USA
[17] Stanford Univ, Dept Orthopaed Surg, Sch Med, Stanford, CA 94305 USA
[18] Stanford Univ, Hosp & Clin, Orthopaed Spine Ctr, Stanford, CA 94305 USA
[19] Stanford Univ, Hosp & Clin, Spinal Surg Serv, Stanford, CA 94305 USA
[20] Univ Calif Irvine, Dept Neurol, Irvine, CA 92717 USA
[21] Univ Calif Los Angeles, Sch Publ Hlth, Dept Epidemiol, Los Angeles, CA 90024 USA