Repeated exposure to sleep restriction followed by recovery sleep – Effects on IL-6 expression and glucocorticoid (GC) sensitivity of monocytes

Abstract

Restricting sleep on week days and catching up on sleep on weekend days is a highly prevalent pattern in work and school populations. We hypothesized that the repeated exposure to such patterns progressively increases the inflammatory response, due to reduced GC sensitivity of monocytes. Fourteen participants (age 25 ± 1 yrs) completed two 25-day-in-hospital periods; sleep-restriction and control-sleep in randomized order. The sleep-restriction condition consisted of three weekly cycles of 5 days with 4 h of sleep/night followed by 2 days with 8 h of sleep/night. Blood draws were taken at 11:30 h on the baseline day and the end of each sleep-restriction and recovery-sleep period. The inflammatory response was assessed by interleukin (IL)-6 positive monocytes (determined by flow cytometry); GC sensitivity of monocytes was determined by measuring the ability of dexamethasone to suppress lipopolysaccharide-stimulated IL-6 expression. IL-6 positive monocytes increased in the second and third week of sleep-restriction over control-sleep by 15% and 20%, respectively (both p 0.05), and did not return to baseline levels during intermittent recovery-sleep. GC sensitivity of monocytes was increased across all 3 weeks of sleep-restriction when compared to control-sleep, and did not normalize during intermittent recovery-sleep periods (all p 0.05). In conclusion, despite an increase in the sensitivity of monocytes to the counter-inflammatory GC signal, monocytes still express more IL-6 in response to repeated exposure of sleep-restriction. Importantly, recovery-sleep does not normalize these changes.