title: The Impact of Sleep Restriction and Simulated Physical Firefighting Work on Acute Inflammatory Stress Responses.
abstract: OBJECTIVE
  This study investigated the effect restricted sleep has on wildland firefighters' acute cytokine levels during 3 days and 2 nights of simulated physical wildfire suppression work.
  
  
  METHODS
  Firefighters completed multiple days of physical firefighting work separated by either an 8-h (Control condition; n = 18) or 4-h (Sleep restriction condition; n = 17) sleep opportunity each night. Blood samples were collected 4 times a day (i.e., 06:15, 11:30, 18:15, 21:30) from which plasma cytokine levels (IL-6, IL-8, IL-1β, TNF-α, IL-4, IL-10) were measured.
  
  
  RESULTS
  The primary findings for cytokine levels revealed a fixed effect for condition that showed higher IL-8 levels among firefighters who received an 8-h sleep each night. An interaction effect demonstrated differing increases in IL-6 over successive days of work for the SR and CON conditions. Fixed effects for time indicated that IL-6 and IL-4 levels increased, while IL-1β, TNF-α and IL-8 levels decreased. There were no significant effects for IL-10 observed.
  
  
  CONCLUSIONS
  Findings demonstrate increased IL-8 levels among firefighters who received an 8-h sleep when compared to those who had a restricted 4-h sleep. Firefighters' IL-6 levels increased in both conditions which may indicate that a 4-h sleep restriction duration and/or period (i.e., 2 nights) was not a significant enough stressor to affect this cytokine. Considering the immunomodulatory properties of IL-6 and IL-4 that inhibit pro-inflammatory cytokines, the rise in IL-6 and IL-4, independent of increases in IL-1β and TNF-α, could indicate a non-damaging response to the stress of simulated physical firefighting work. However, given the link between chronically elevated cytokine levels and several diseases, further research is needed to determine if firefighters' IL-8 and IL-6 levels are elevated following repeated firefighting deployments across a fire season and over multiple fire seasons.
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, 221 Burwood Hwy, Burwood, VIC 3125, Australia; Bushfire Co-Operative Research Centre, East Melbourne 3002, Australia.
authors.forename: Alexander
authors.initials: A
authors.lastname: Wolkow
authors.affiliation: Bushfire Co-Operative Research Centre, East Melbourne 3002, Australia; Central Queensland University, Appleton Institute, Wayville 5034, Australia.
authors.forename: Sally A
authors.initials: SA
authors.lastname: Ferguson
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, 221 Burwood Hwy, Burwood, VIC 3125, Australia; Bushfire Co-Operative Research Centre, East Melbourne 3002, Australia.
authors.forename: Grace E
authors.initials: GE
authors.lastname: Vincent
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, 221 Burwood Hwy, Burwood, VIC 3125, Australia; Bushfire Co-Operative Research Centre, East Melbourne 3002, Australia.
authors.forename: Brianna
authors.initials: B
authors.lastname: Larsen
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, 221 Burwood Hwy, Burwood, VIC 3125, Australia; Bushfire Co-Operative Research Centre, East Melbourne 3002, Australia.
authors.forename: Brad
authors.initials: B
authors.lastname: Aisbett
authors.affiliation: Centre for Physical Activity and Nutrition Research, Deakin University, 221 Burwood Hwy, Burwood, VIC 3125, Australia.
authors.forename: Luana C
authors.initials: LC
authors.lastname: Main
mesh_terms: D000328:Adult; D016207:Cytokines / Q000097:blood*; D004032:Diet; D005260:Female; D061388:Firefighters; D006801:Humans; D007249:Inflammation / Q000276:immunology; D053583:Interleukin-1beta / Q000097:blood; D015847:Interleukin-4 / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D011897:Random Allocation; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000097:blood / Q000276:immunology*; D040701:Stress Disorders, Traumatic, Acute / Q000097:blood / Q000276:immunology*; D013312:Stress, Physiological / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000097:blood
chemical_list: D016207:Cytokines; C508585:IL1B protein, human; C508598:IL4 protein, human; C508600:IL6 protein, human; D053583:Interleukin-1beta; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D015847:Interleukin-4