The impact of sleep restriction and simulated physical firefighting work on acute inflammatory stress responses

Wolkow, Alexander and Ferguson, Sally A. and Vincent, Grace E. and Larsen, Brianna and Aisbett, Brad and Main, Luana C. (2015) The impact of sleep restriction and simulated physical firefighting work on acute inflammatory stress responses. PLoS One, 10 (9):e0138128. pp. 1-17.

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Abstract

Objectives
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.

Conclusion
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.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 20 Sep 2020 23:47
Last Modified: 21 Sep 2020 00:19
Uncontrolled Keywords: pituitary-adrenal axis; c-reactive protein; blood-cell count; antiinflammatory cytokines; wildfire suppression; capillary blood; heart-disease; healthy-men; interleukin-6; deprivation
Fields of Research (2008): 11 Medical and Health Sciences > 1106 Human Movement and Sports Science > 110602 Exercise Physiology
11 Medical and Health Sciences > 1117 Public Health and Health Services > 111705 Environmental and Occupational Health and Safety
Socio-Economic Objectives (2008): C Society > 92 Health > 9205 Specific Population Health (excl. Indigenous Health) > 920505 Occupational Health
Identification Number or DOI: 10.1371/journal.pone.0138128
URI: http://eprints.usq.edu.au/id/eprint/39606

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