Sleep restriction increases the risk of developing cardiovascular diseases by augmenting proinflammatory responses through IL-17 and CRP

Abstract

Background: Sleep restriction, leading to deprivation of sleep, is common in modern 24-h societies and is associated with the development of health problems including cardiovascular diseases. Our objective was to investigate the immunological effects of prolonged sleep restriction and subsequent recovery sleep, by simulating a working week and following recovery weekend in a laboratory environment.

Methods and findings: After 2 baseline nights of 8 hours time in bed (TIB), 13 healthy young men had only 4 hours TIB per night for 5 nights, followed by 2 recovery nights with 8 hours TIB. 6 control subjects had 8 hours TIB per night throughout the experiment. Heart rate, blood pressure, salivary cortisol and serum C-reactive protein (CRP) were measured after the baseline (BL), sleep restriction (SR) and recovery (REC) period. Peripheral blood mononuclear cells (PBMC) were collected at these time points, counted and stimulated with PHA. Cell proliferation was analyzed by thymidine incorporation and cytokine production by ELISA and RT-PCR. CRP was increased after SR (145% of BL; p<0.05), and continued to increase after REC (231% of BL; p<0.05). Heart rate was increased after REC (108% of BL; p<0.05). The amount of circulating NK-cells decreased (65% of BL; p<0.005) and the amount of B-cells increased (121% of BL; p<0.005) after SR, but these cell numbers recovered almost completely during REC. Proliferation of stimulated PBMC increased after SR (233% of BL; p<0.05), accompanied by increased production of IL-1beta (137% of BL; p<0.05), IL-6 (163% of BL; p<0.05) and IL-17 (138% of BL; p<0.05) at mRNA level. After REC, IL-17 was still increased at the protein level (119% of BL; p<0.05).

Conclusions: 5 nights of sleep restriction increased lymphocyte activation and the production of proinflammatory cytokines including IL-1beta IL-6 and IL-17; they remained elevated after 2 nights of recovery sleep, accompanied by increased heart rate and serum CRP, 2 important risk factors for cardiovascular diseases. Therefore, long-term sleep restriction may lead to persistent changes in the immune system and the increased production of IL-17 together with CRP may increase the risk of developing cardiovascular diseases.

Figure 1. Cell distribution of PBMC.

Number of T cells, B cells, and natural killer (NK) cells in PBMC, expressed as percentage of participant's individual baseline values. SR = sleep restriction, REC = recovery, Con = control group, Exp = sleep restriction group. Data are presented as mean values ±SEM. * p<0.05.

Figure 2. PBMC proliferation and hs-CRP.

Proliferation of PBMC after stimulation with phytohaemagglutinin (PHA, 45 µg/mL) and high sensitivity C-reactive protein (hs-CRP) concentrations in plasma. SR = sleep restriction, REC = recovery, Con = control group, Exp = sleep restriction group. Data are expressed as percentages of participant's individual baseline values (mean±SEM). * p<0.05.

Figure 3. Cytokine mRNA and protein expression.

Cytokine mRNA and protein expression of phytohaemagglutinin (PHA, 45 µg/mL) activated PBMC. SR = sleep restriction, REC = recovery, Con = control group, Exp = sleep restriction group. Data are expressed as percentages of participant's individual baseline values (mean±SEM). * p<0.05.

Figure 4. From sleep restriction to cardiovascular diseases.

Schematic flow chart showing the proposed mechanism explaining how sleep restriction may ultimately evoke increased cardiovascular morbidity.