title: Transient immune impairment after a simulated long-haul flight.
abstract: BACKGROUND
  Almost 2 billion people travel aboard commercial airlines every year, with about 20% developing symptoms of the common cold within 1 wk after air travel. We hypothesize that hypobaric hypoxic conditions associated with air travel may contribute to immune impairment.
  
  
  METHODS
  We studied the effects of hypobaric hypoxic conditions during a simulated flight at 8000 ft (2438 m) cruising altitude on immune and stress markers in 52 healthy volunteers (mean age 31) before and on days 1, 4, and 7 after the flight. We did a cohort study using a generalized estimating equation to examine the differences in the repeated measures.
  
  
  RESULTS
  Our findings show that the hypobaric hypoxic conditions of a 10-h overnight simulation flight are not associated with severe immune impairment or abnormal IgA or cortisol levels, but with transient impairment in some parameters: we observed a transient decrease in lymphocyte proliferative responses combined with an upregulation in CD69 and CD14 cells and a decrease in HLA-DR in the immediate days following the simulated flight that normalized by day 7 in most instances.
  
  
  CONCLUSIONS
  These transient immune changes may contribute to an increased susceptibility to respiratory infections commonly seen after long-haul flights.
authors.affiliation: Department of Medicine, National University Singapore, Yong Loo Lin School of Medicine, Singapore. epvws@pacific.net.sg
authors.forename: Annelies
authors.initials: A
authors.lastname: Wilder-Smith
authors.forename: Fatima B
authors.initials: FB
authors.lastname: Mustafa
authors.forename: Chung Mien
authors.initials: CM
authors.lastname: Peng
authors.forename: Arul
authors.initials: A
authors.lastname: Earnest
authors.forename: David
authors.initials: D
authors.lastname: Koh
authors.forename: Gen
authors.initials: G
authors.lastname: Lin
authors.forename: Iqbal
authors.initials: I
authors.lastname: Hossain
authors.forename: Paul A
authors.initials: PA
authors.lastname: MacAry
mesh_terms: D000328:Adult; D000368:Aged; D000401:Aircraft; D000531:Altitude; D015703:Antigens, CD / Q000032:analysis; D001273:Atmosphere Exposure Chambers; D015415:Biomarkers / Q000032:analysis; D001772:Blood Cell Count; D005260:Female; D005434:Flow Cytometry; D006684:HLA-DR Antigens / Q000032:analysis; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis; D000860:Hypoxia / Q000276:immunology*; D007070:Immunoglobulin A / Q000032:analysis; D008297:Male; D008875:Middle Aged
chemical_list: D015703:Antigens, CD; D015415:Biomarkers; D006684:HLA-DR Antigens; D007070:Immunoglobulin A; D006854:Hydrocortisone