Influence of Circadian Misalignment on Sleep, Energy Expenditure, Thermoregulatory Physiology and Cognition
Year: 2014
Type: dissertation
Abstract: Demands of modern society force many work operations into the late night when the intrinsic circadian timing system is promoting sleep. Overnight shiftwork is associated with increased risk for adverse metabolic health, accidents and injury, and sleep disruption. Uncovering potential physiological mechanisms by which working and eating at adverse circadian times contribute to metabolic dysregulation are vital to the development of treatment strategies. Furthermore, understanding the time course of cognitive performance decrements during shiftwork and mechanisms by which caffeine improves alertness and disrupts sleep are important for developing evidence-based fatigue management approaches. Therefore, the aims of this dissertation were to: 1) determine fundamental changes in physiology that would promote a state of unwanted weight gain in response to food consumed during simulated overnight shiftwork; 2) determine how cognitive performance changes during extended wakefulness on the transition to the first night shift and during subsequent night shifts; and 3) determine if early morning caffeine administration influences the distal-proximal skin temperature gradient and improves alertness while subsequently disrupting daytime recovery sleep.\nThe results indicate: 1) working during the night increased total daily energy expenditure (EE) on the transition to the first nightshift day and decreased total daily EE on the second and third nightshifts, decreased EE during daytime sleep episodes, decreased EE in response to a late dinner meal, increased total daily fat utilization on the first and second nightshifts and reduced carbohydrate and protein utilization on the second nightshift, and decreased subjective hunger despite concurrent decreases in satiety hormones; 2) working during the night increased sleepiness and decreased cognitive performance which predominately did not change across subsequent nightshifts; and 3) caffeine administered 5h prior to daytime recovery sleep significantly decreased the distal-proximal skin temperature gradient, increased alertness, and disrupted daytime recovery sleep.\nThese findings suggest that reduced energy expenditure during nightshift work may represent a contributing mechanism by which working and eating during the night increases the risk of weight gain and obesity. Furthermore, results from this dissertation expand our knowledge on cognitive performance decrements across subsequent night shifts and physiological mechanisms by which caffeine improves alertness and disturbs sleep.
Author: McHill, Andrew William
Language: English
Subfield: Experimental and Cognitive Psychology
Field: Psychology
Domain: Social Sciences
Open Access status: green
Funders: National Institutes of Health, Directorate for Biological Sciences, University of Colorado Boulder, National Heart, Lung, and Blood Institute, National Institute of Diabetes and Digestive and Kidney Diseases, National Center for Research Resources, National Center for Advancing Translational Sciences
OpenAlex ID: W2522720938