Accepted for Publication: July 11, 2012.
Author Contributions:Study concept and design: N. J. O. Birkmeyer, Genaw, and J. D. Birkmeyer. Acquisition of data: N. J. O. Birkmeyer, Chengelis, and Schram. Analysis and interpretation of data: N. J. O. Birkmeyer, Finks, Carlin, Chengelis, Krause, Hawasli, Genaw, English, Schram, and J. D. Birkmeyer. Drafting of the manuscript: N. J. O. Birkmeyer. Critical revision of the manuscript for important intellectual content: N. J. O. Birkmeyer, Finks, Carlin, Chengelis, Krause, Hawasli, Genaw, English, Schram, and J. D. Birkmeyer. Statistical analysis: N. J. O. Birkmeyer, Krause, and J. D. Birkmeyer. Obtained funding: N. J. O. Birkmeyer. Administrative, technical, and material support: N. J. O. Birkmeyer, Genaw, and Schram. Study supervision: N. J. O. Birkmeyer, Finks, Carlin, and Schram.
Michigan Bariatric Surgery Collaborative Sites: Kalamazoo, Michigan: Borgess Medical Center and Bronson Methodist Hospital; Saginaw, Michigan: Covenant Healthcare; Troy, Michigan: Crittenton Hospital Medical Center and William Beaumont Hospital, Troy; Pontiac: Doctor's Hospital of Michigan and St Joseph Mercy Oakland; Ypsilanti, Michigan: Forest Health Medical Center; Alma: Mid Michigan Medical Center–Gratiot; Detroit, Michigan: Harper University Hospital, Henry Ford Hospital, and Henry Ford West Bloomfield Hospital; Wyandotte, Michigan: Henry Ford Wyandotte Hospital; Flint, Michigan: Hurley Medical Center and McLaren Regional Medical Center; West Bloomfield, Michigan: Huron Valley–Sinai Hospital; Niles, Michigan: Lakeland Community Hospital; Marquette, Michigan: Marquette General Hospital; Mount Clemens, Michigan: McLaren Macomb Hospital; Muskegon, Michigan: Mercy Health Partners; Wyoming, Michigan: Metro Health (Grand River Surgery); Midland: Mid Michigan Medical Center– Midland; Traverse City, Michigan: Munson Medical Center (Grand Traverse Surgery); Grand Haven, Michigan: North Ottawa Community Health System; Dearborn, Michigan: Oakwood Hospital; Port Huron: Port Huron Hospital (Lap Band Center of Michigan) and St Joseph Mercy–Port Huron; Madison Heights, Michigan: Providence Hospital and Medical Center; East Lansing, Michigan: Sparrow Weight Management Center; Grand Rapids, Michigan: Spectrum Health and St Mary's Health Care–Grand Rapids; Zeeland, Michigan: Spectrum Health Zeeland; St Clair Shores, Michigan: St John Hospital and Medical Center (Eastside Surgical Specialists); Madison Heights, Michigan: St John Weight Loss Center; Livonia, Michigan: St Mary Mercy Hospital; Ann Arbor: University of Michigan; Sault Ste Marie, Michigan: War Memorial Hospital; Grosse Pointe, Michigan: William Beaumont Hospital, Grosse Pointe; and Royal Oak, Michigan: William Beaumont Hospital, Royal Oak.
Conflict of Interest Disclosures: None reported.