Total sleep deprivation induces an acute and transient increase in NK cellactivity in healthy young volunteers

Study Objectives: To investigate the effects of one night's total sleep dep rivation (TSD) on NK cell activity, with rigorous control of circadian phas e of sampling points as well as physical exercise level in association with sleep deprivation. Design: The mean sleep onset time of each subject before starting the study was defined as his 0000 h. This study was composed of a Sleep-Sleep sessio n (sleep times, 00:00 h - 08:00 h and 24:00 h - 32:00 h) and a Sleep-Wake s ession (sleep time, 00:00 h - 08:00 h) with TSD (24:00 h 32:00 h) placed in a cross-over design with 2-week interval between each session. In each ses sion, the subjects were rested in the supine position under dim light from - 06:00 h to 36:00 h (for 42 hours). Setting: University-based sleep and chronobiology laboratory Participants: 10 healthy adult men (mean age, 20.9 y; age range, 19-23 y) Interventions: N/A Measurements and Results: NK cell activity was measured every 4 hours from 12:00 h. NK cell activity during TSD (at 28:00 h) has been revealed to sign ificantly increase (p=0.01) compared with the corresponding value in the Sl eep-Sleep session. This effect was weaker at their usual waking time 32:00 h (p=0.07), and disappeared until 36:00 h (4 hours after awakening). The ci rcadian rhythm phases (dim light melatonin onset time) were coincident betw een the 2 sessions. Conclusions: The present findings suggest that one night TSD induces an acu te and transient increase in NK cell activity that is not influenced by the effects of circadian rhythm or the amount of physical exercise undertaken during TSD.