title: Improved survival in heart transplant patients living at high altitude.
abstract: OBJECTIVE
  Higher altitudes are associated with chronic hypoxia and elevated pulmonary vascular resistance, both potentially detrimental to patients requiring heart transplantation. The purpose of the present study was to determine whether altitude negatively affects survival among patients undergoing heart transplantation.
  
  
  METHODS
  The United Network of Organ Sharing database for adult patients undergoing heart transplantation from 1990 to 2008 (n = 36,529) was analyzed, and each patient was assigned an altitude according to their home ZIP code. Survival was compared between patients at less than 2000 ft, 2000 or more to less than 4000 ft, and 4000 ft or more. Adjusted survival was calculated using Cox proportional hazards analysis with propensity-matched stratification.
  
  
  RESULTS
  Patients living at above 2000 ft had a 16% reduction in the risk of death at 1 year after transplant (P = .006) compared with those at lower altitudes. At 5 and 10 years, the risk reduction was 6% (P = .21) and 6% (P = .114), respectively. Among patients living above 4000 ft, the 1-, 5-, and 10-year reduction in the risk of death was 20% (P = .022), 12% (P = .057), and 15% (P = .0052) compared with those living below 2000 ft, respectively. Patients at high altitude had a lower incidence of diabetes, used tobacco less often, and accounted for the greatest proportion of status 2 heart transplants. Comparing the factors predicting survival at high and low altitudes, patients with a status 1A listing had improved outcomes at higher altitudes.
  
  
  CONCLUSIONS
  Patients living above 2000 ft have improved survival after heart transplantation, an advantage even more pronounced at 4000 ft. Although the mechanism of protection remains unclear, the findings might reflect differences in pre-2006 organ allocation.
authors.affiliation: Division of Cardiothoracic Surgery, University of Utah, Salt Lake City, UT 84132-2101, USA.
authors.forename: Curtis J
authors.initials: CJ
authors.lastname: Wozniak
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Baird
authors.forename: Josef
authors.initials: J
authors.lastname: Stehlik
authors.forename: Stavros G
authors.initials: SG
authors.lastname: Drakos
authors.forename: David A
authors.initials: DA
authors.lastname: Bull
authors.forename: Amit N
authors.initials: AN
authors.lastname: Patel
authors.forename: Craig H
authors.initials: CH
authors.lastname: Selzman
mesh_terms: D000328:Adult; D000531:Altitude; D016009:Chi-Square Distribution; D019992:Databases as Topic; D005260:Female; D016027:Heart Transplantation / Q000009:adverse effects / Q000401:mortality*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D057216:Propensity Score; D016016:Proportional Hazards Models; D012111:Residence Characteristics; D018570:Risk Assessment; D012307:Risk Factors; D016019:Survival Analysis; D015996:Survival Rate; D013997:Time Factors; D009927:Tissue and Organ Procurement; D016896:Treatment Outcome; D014481:United States