title: Seasonal variation in surgical outcomes as measured by the American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP).
abstract: OBJECTIVE
  We hypothesize that the systems of care within academic medical centers are sufficiently disrupted with the beginning of a new academic year to affect patient outcomes.
  
  
  METHODS
  This observational multiinstitutional cohort study was conducted by analysis of the National Surgical Quality Improvement Program-Patient Safety in Surgery Study database. The 30-day morbidity and mortality rates were compared between 2 periods of care: (early group: July 1 to August 30) and late group (April 15 to June 15). Patient baseline characteristics were first compared between the early and late periods. A prediction model was then constructed, via stepwise logistic regression model with a significance level for entry and a significance level for selection of 0.05.
  
  
  RESULTS
  There was 18% higher risk of postoperative morbidity in the early (n = 9941) versus the late group (n = 10313) (OR 1.18, 95%, CI 1.07-1.29, P = 0.0005, c-index 0.794). There was a 41% higher risk for mortality in the early group compared with the late group (OR 1.41, CI 1.11-1.80, P = 0.005, c-index 0.938). No significant trends in patient risk over time were noted.
  
  
  CONCLUSIONS
  Our data suggests higher rates of postsurgical morbidity and mortality related to the time of the year. Further study is needed to fully describe the etiologies of the seasonal variation in outcomes.
authors: Department of Surgery, University of Michigan Health System, Ann Arbor, MI 48109-0331, USA.englesbe@med.umich.edu
authors: Michael J
authors: MJ
authors: Englesbe
authors: Shawn J
authors: SJ
authors: Pelletier
authors: John C
authors: JC
authors: Magee
authors: Paul
authors: P
authors: Gauger
authors: Tracy
authors: T
authors: Schifftner
authors: William G
authors: WG
authors: Henderson
authors: Shukri F
authors: SF
authors: Khuri
authors: Darrell A
authors: DA
authors: Campbell
mesh_terms: D016009:Chi-Square Distribution; D017598:Efficiency, Organizational; D005260:Female; D013502:General Surgery / Q000592:standards*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009873:Operating Rooms / Q000458:organization & administration; D017063:Outcome Assessment, Health Care; D011183:Postoperative Complications / Q000453:epidemiology* / Q000401:mortality; D011785:Quality Assurance, Health Care; D012044:Regression Analysis; D012621:Seasons; D012955:Societies, Medical; D014481:United States / Q000453:epidemiology
references: Anesthesiology. 2004 Nov;101(5):1210-4
references: 15505458
references: J Am Coll Surg. 2004 Oct;199(4):531-7
references: 15454134
references: JAMA. 1990 Feb 16;263(7):953-7
references: 2299762
references: Lancet. 1991 Jul 6;338(8758):9-13
references: 1676131
references: Med Care. 1993 Jan;31(1):73-83
references: 8417272
references: Lancet. 1994 Apr 16;343(8903):975
references: 7909025
references: J Am Coll Surg. 1997 Oct;185(4):315-27
references: 9328380
references: Ann Surg. 1998 Oct;228(4):491-507
references: 9790339
references: Int J Aviat Psychol. 1999;9(1):19-32
references: 11541445
references: Ann Intern Med. 2004 Dec 7;141(11):851-7
references: 15583227
references: J Vasc Surg. 2005 Mar;41(3):382-9
references: 15838467
references: Ann Surg. 2005 Jun;241(6):1024-7; discussion 1027-8
references: 15912052
references: Surgery. 2005 Nov;138(5):837-43
references: 16291383
references: Cancer. 2006 Jun 1;106(11):2476-81
references: 16634089
references: JAMA. 2006 Jul 5;296(1):72-8
references: 16820549
references: Surgery. 2006 Jul;140(1):25-33
references: 16857439
references: Int J Epidemiol. 2000 Apr;29(2):274-9
references: 10817125
references: Surgery. 2001 Aug;130(2):346-53
references: 11490370
references: Ann Surg. 2001 Sep;234(3):370-82; discussion 382-3
references: 11524590
references: Am J Crit Care. 2001 Nov;10(6):376-82
references: 11688604
references: Int J Epidemiol. 2001 Oct;30(5):1109-16
references: 11689530
references: N Engl J Med. 2002 Apr 11;346(15):1128-37
references: 11948273
references: Hum Factors. 2001 Winter;43(4):641-74
references: 12002012
references: Ann Surg. 2002 Sep;236(3):344-53; discussion 353-4
references: 12192321
references: JAMA. 2002 Oct 23-30;288(16):1987-93
references: 12387650
references: Health Serv Res. 2002 Dec;37(6):1553-81
references: 12546286
references: Am J Surg. 2003 Aug;186(2):169-74
references: 12885613
references: J Gen Intern Med. 2003 Aug;18(8):639-45
references: 12911646
references: JAMA. 2003 Sep 24;290(12):1617-23
references: 14506121
references: N Engl J Med. 2003 Nov 27;349(22):2117-27
references: 14645640
references: Br Med J (Clin Res Ed). 1982 Oct 2;285(6346):919-23
references: 6811068