Diurnal rhythms in blood cell populations and the effect of acute sleep deprivation in healthy young men

Abstract

Study objectives: The sleep/wake cycle is accompanied by changes in circulating numbers of immune cells. The goal of this study was to provide an in-depth characterization of diurnal rhythms in different blood cell populations and to investigate the effect of acute sleep deprivation on the immune system, as an indicator of the body's acute stress response.

Design: Observational within-subject design.

Setting: Home environment and Clinical Research Centre.

Participants: 15 healthy male participants aged 23.7 ± 5.4 (standard deviation) yr.

Interventions: Total sleep deprivation.

Measurements and results: Diurnal rhythms of several blood cell populations were assessed under a normal sleep/wake cycle followed by 29 hr of extended wakefulness. The effect of condition (sleep versus sleep deprivation) on peak time and amplitude was investigated. Interindividual variation of, and the level of correlation between, the different cell populations was assessed. Comprehensive nonlinear curve fitting showed significant diurnal rhythms for all blood cell types investigated, with CD4 (naïve) cells exhibiting the most robust rhythms independent of condition. For those participants exhibiting significant diurnal rhythms in blood cell populations, only the amplitude of the granulocyte rhythm was significantly reduced by sleep deprivation. Granulocytes were the most diverse population, being most strongly affected by condition, and showed the lowest correlations with any other given cell type while exhibiting the largest interindividual variation in abundance.

Conclusions: Granulocyte levels and diurnal rhythmicity are directly affected by acute sleep deprivation; these changes mirror the body's immediate immune response upon exposure to stress.

Keywords: Human; circadian; flow cytometry; granulocytes.

Figure 1

Full laboratory protocol. Black bars indicate sleep periods, 0 lux; gray bars, wake periods in a semirecumbent position, < 5 lux; white bars, free movement and wake, 100 lux; ▴controlled meals; — blood sampling period.

Figure 2

Changes in granulocyte population for each participant over the 48-hr sampling period. For better comparability, cell counts per time point were calculated as a fraction of the mean for each individual. The gray bars indicate wake periods in a semi-recumbent position, < 5 lux; the black bar indicates the sleep period, recumbent position, 0 lux. Note the elevated values in some of the subjects during the sleep deprivation part of the study.

Figure 3

Nonlinear curve fitting of z-scored blood cell counts. Changes in abundance over the 48-hr sampling period are given for each cell (sub)population under study. Gray lines indicate individual patterns; black lines indicate the cosine curve fitted to the data points for all 10 individuals.

Figure 4

Heat plot for visualization of the correlation matrix. Higher correlation between independent cell types is depicted by darker squares. Rows and columns are sorted by the mean correlation coefficient per row, which is the same per corresponding column.