Research
The impact of shift work induced chronic circadian disruption on IL-6 and TNF-α immune responses
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* Corresponding author: Anke van Mark anke.van.mark@arbeitsmedizin.uni-luebeck.de
1 Institute of Occupational Medicine, University of Lübeck, 23538 Lübeck, Ratzeburger Allee 160, Germany
2 AUDI AG Ingolstadt, 85045 Ingolstadt, Germany
3 Department of Psychiatry and Psychotherapy, University of Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany
4 Institute of Occupational Medicine, Charité - Universitätsmedizin Berlin, Free University and Humboldt-University, 14195 Berlin, Thielallee 73, Germany
5 European Research Society for Environment and Health in Transportation (EUGT) e. V., 14195 Berlin, Thielallee 73, Germany
6 Clinical Infectious Diseases, Research Center Borstel, 23845 Borstel, Germany
Journal of Occupational Medicine and Toxicology 2010, 5:18 doi:10.1186/1745-6673-5-18
Published: 5 July 2010Abstract
AIM
Sleep disturbances induce proinflammatory immune responses, which might increase cardiovascular disease risk. So far the effects of acute sleep deprivation and chronic sleep illnesses on the immune system have been investigated. The particular impact of shift work induced chronic circadian disruption on specific immune responses has not been addressed so far.
Methods
Pittsburgh-Sleep-Quality-Index (PSQI) questionnaire and blood sampling was performed by 225 shift workers and 137 daytime workers. As possible markers the proinflammatory cytokines IL-6 and TNF-α and lymphocyte cell count were investigated. A medical examination was performed and biometrical data including age, gender, height, weight, waist and hip circumference and smoking habits were collected by a structured interview.
Results
Shift workers had a significantly higher mean PSQI score than day workers (6.73 vs. 4.66; p < 0.001). Day workers and shift workers had similar serum levels of IL-6 (2.30 vs. 2.67 resp.; p = 0.276), TNF-α (5.58 vs. 5.68, resp.; p = 0.841) or lymphocytes count (33.68 vs. 32.99, resp.; p = 0.404). Furthermore there were no differences in cytokine levels (IL-6 p = 0.761; TNF-α p = 0.759) or lymphocyte count (p = 0.593) comparing the sleep quality within the cohorts. When this calculation of sleep quality was stratified by shift and day workers irrespective of their sleep quality day workers and shift workers had similar serum levels of IL-6, TNF-α or lymphocytes count. Multiple linear regression analysis showed a significant correlation of lymphocytes count and smoking habits.
Conclusion
Shift work induces chronic sleep debt. Our data reveals that chronic sleep debt might not always lead to an activation of the immune system, as we did not observe differences in lymphocyte count or level of IL-6 or TNF-α serum concentration between shift workers and day workers. Therefore chronic sleep restriction might be eased by a long-term compensating immune regulation which (in healthy) protects against an overstimulation of proinflammatory immune mechanisms and moderates metabolic changes, as they are known from short-term sleep deprivation or sleep related breathing disorders.