Sleep loss mirrors stress affects on immune system

By Lucy Piper

Acute sleep loss affects the immune system in a similar way to stress, researchers report.

Studying the white blood cells of healthy young men under a normal sleep/wake cycle and following 29 hours of being awake, they found that sleep loss significantly affected the diurnal rhythm in granulocyte number.

"We have demonstrated that granulocyte rhythmicity is severely affected by acute sleep deprivation, with higher circulating levels, lower amplitudes, and loss of rhythmicity," the team explains in Sleep.

"Future research will reveal the molecular mechanisms behind this immediate stress response and elucidate its role in the development of diseases associated with chronic sleep loss."

The 15 men, aged an average of 24 years, participating in the study followed a strict schedule of 8 hours of sleep every day for a week to stabilize their circadian clocks and minimize sleep deprivation.

They were then kept awake for a 29-hour period. White blood cell counts during this period, compared with no sleep deprivation, showed a significant effect on the amplitude of white blood cells, which could be explained by a significant increase in the granulocyte population during this time. Amplitudes of all the other independent white blood cell types were not statistically significant.

Indeed, granulocytes were the white blood cell type most affected by sleep deprivation, demonstrating the biggest loss in both rhythmicity and amplitude (from 0.88 to 0.49 during sleep deprivation), while CD4 cells were the least affected.

Granulocytes also showed the weakest correlations with the other white blood cell types and exhibited the largest interindividual variation in abundance, ranging from approximately 30% up to 80% of the percentage of white blood cells.

"We show for the first time that the diurnal rhythm in granulocyte numbers is significantly affected by sleep loss, exhibiting lower amplitude and loss of rhythmicity, and this is accompanied by an overall increase in the circulating levels of granulocytes," say Katrin Ackermann, from Erasmus MC University Medical Centre in Rotterdam, the Netherlands, and colleagues.

"Our findings suggest that the observed changes in granulocyte levels directly mirror the body's immediate immune response upon exposure to stress."

They conclude: "This will have implications for clinical practice and for professions associated with long-term sleep loss such as rotating shift workers."

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