title: Seasonal variation influences outcomes following lung cancer resections.
abstract: OBJECTIVE
  The effect of seasonal variation on postoperative outcomes following lung cancer resections is unknown. We hypothesized that postoperative outcomes following surgical resection for lung cancer within the United States would not be impacted by operative season.
  
  
  METHODS
  From 2002 to 2007, 182507 isolated lung cancer resections (lobectomy (n = 147 937), sublobar resection (n = 21650), and pneumonectomy (n = 13916)) were evaluated using the Nationwide Inpatient Sample (NIS) database. Patients were stratified according to operative season: spring (n = 47382), summer (n = 46131), fall (n = 45370) and winter (n = 43624). Multivariate regression models were applied to assess the effect of operative season on adjusted postoperative outcomes.
  
  
  RESULTS
  Patient co-morbidities and risk factors were similar despite the operative season. Lobectomy was the most common operation performed: spring (80.0%), summer (81.3%), fall (81.8%), and winter (81.1%). Lung cancer resections were more commonly performed at large, high-volume (>75th percentile operative volume) centers (P < 0.001). Unadjusted mortality was lowest during the spring (2.6%, P < 0.001) season compared with summer (3.1%), fall (3.0%) and winter (3.2%), while complications were most common in the fall (31.7%, P < 0.001). Hospital length of stay was longest for operations performed in the winter season (8.92 ± 0.11 days, P < 0.001). Importantly, multivariable logistic regression revealed that operative season was an independent predictor of in-hospital mortality (P < 0.001) and of postoperative complications (P < 0.001). Risk-adjusted odds of in-hospital mortality were increased for lung cancer resections occurring during all other seasons compared with those occurring in the spring.
  
  
  CONCLUSIONS
  Outcomes following surgical resection for lung cancer are independently influenced by time of year. Risk-adjusted in-hospital mortality and hospital length of stay were lowest during the spring season.
authors.affiliation: Division of Thoracic and Cardiovascular Surgery, Department of Surgery, University of Virginia Health System, Charlottesville, VA, USA.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: LaPar
authors.forename: Alykhan S
authors.initials: AS
authors.lastname: Nagji
authors.forename: Castigliano M
authors.initials: CM
authors.lastname: Bhamidipati
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Kozower
authors.forename: Christine L
authors.initials: CL
authors.lastname: Lau
authors.forename: Gorav
authors.initials: G
authors.lastname: Ailawadi
authors.forename: David R
authors.initials: DR
authors.lastname: Jones
mesh_terms: D000368:Aged; D015897:Comorbidity; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008175:Lung Neoplasms / Q000401:mortality / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011013:Pneumonectomy / Q000009:adverse effects* / Q000379:methods / Q000401:mortality; D011183:Postoperative Complications / Q000453:epidemiology; D012621:Seasons; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology