Pavlis, Alexia (2007) Cognitive, neuroanatomical and neuroendocrine effects of long-term rotating shift work in a nursing sample. Other Degree thesis, Victoria University.

Abstract

Sleep disruption, like that experienced by long-term rotating shift workers, is a physiological stressor which causes a variety of adverse physical, psychological and cognitive symptoms. Some cognitive symptoms are thought to be mediated by the direct effect of stress hormones on the hippocampus. Regardless of its source, stress provokes endocrine responses in the body that affect the hypothalamic-pituitary-adrenal (HPA) axis. Whereas acute activation of the HPA axis adaptively activates the body’s stress response by increasing cortisol production, prolonged or repeated activation is detrimental to health due to dysregulation of the HPA axis. Cortisol affects the hippocampus, which has a high concentration of glucocorticoid receptors and plays a prominent role in the down-regulation of the HPA axis. Overstimulation of glucocortioid receptors can cause hippocampal atrophy and related cognitive deficits. Research has found that air crew with inadequate recovery time between outbound, transmeridian long-haul flights showed performance decrements on cognitive tasks, reduced hippocampal volumes and increased cortisol levels. The current study aimed to investigate whether work-related sleep disruption caused similar effects among rotating shift-workers from outside the flight industry. Twelve long-term female rotating shift-workers (nurses) and 17 day working female control participants (nurses and others) participated in the study. Analyses of the sleep health, cognitive (memory, attention, visual-spatial skills), endocrine (salivary cortisol), magnetic resonance imaging (MRI) and spectroscopy (MRS) data of these participants showed few differences between groups in cognitive performance, volumetric MRI or MRS. Shift workers reported less sleep over a fortnight, higher levels of fatigue and lower levels of vigor compared to controls. Cortisol rhythm changes including earlier morning rise and peak attenuation were apparent in shift workers. The results are interpreted in terms of age differences between the groups and the existence of a 'healthy worker' effect in the shift workers.

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