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Abstract: Sleep disruption is a growing problem that may have serious health effects. As stress-induced increases in cortisol are thought to be a key adaptive process it is important to examine how this response is affected by sleep. The current study investigated the association of four sleep parameters (objective/subjectively measured sleep quality and quantity) and subsequent salivary cortisol reactivity (maximal change from baseline) to an experimental stressor in 53 healthy women. Objective actigraphy monitoring and self-report diaries were used to assess sleep. Results revealed that individuals with lower objective sleep quality (wake percentage during sleep) had a blunted response to the experimental stressor. No associations were found between cortisol reactivity and actigraphy-derived sleep quantity, or either of the self-reported sleep variables. Results are discussed with regard to the possible adverse health effects that may result from poor sleep quality and a blunted cortisol response to stress. [Copyright &y& Elsevier]

Abstract: Sleep is important for health; however, poor sleep is a growing problem in many Western societies, particularly among women. Alterations in immune function following poor sleep (defined by duration and disruption) may be linked to ill health. Not yet investigated are the possible effects on stress-induced mobilization of lymphocytes. As natural killer (NK) cells are particularly responsive to acute stress, the present study examined whether sleep period duration and percentage of time awake after sleep onset (WASO) the night before a laboratory stressor would predict reduced NK cell mobilization. Sleep was monitored by actigraphy in 39 healthy women. NK cell peripheral blood numbers were determined at baseline (post-20min rest), 4min into a Stroop task, immediately post-task and 30min after task completion. Participants with high WASO had significantly less NK cell mobilization to the stressor and failed to return to baseline levels after 30min compared to women with low WASO. No effects were found for sleep period duration. Findings raise the possibility that inadequate NK cell mobilization to, and poor recovery from acute stress may be one pathway by which sleep could impact health. [Copyright &y& Elsevier]