The effect of sleep restriction on postprandial salivary cortisol
Open Access
- Author:
- Perkhalyuk, Nataliya
- Area of Honors:
- Biobehavioral Health
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Orfeu M Buxton, Thesis Supervisor
Helen Marie Kamens, Thesis Honors Advisor - Keywords:
- sleep restriction
hypothalamic pituitary adrenal axis
cortisol
circadian rhythm
postprandial cortisol response - Abstract:
- Restricting sleep to meet the demands of increasingly hectic work schedules is becoming common place in the United States. Sleeping less than the recommended number of hours per night disrupts the circadian rhythm of hormone secretion leading to metabolic impairment. Sleep restriction, defined as sleeping 5 hours/night has been linked to increased risk of developing cardiometabolic disease. Previous studies found that one week of sleep restriction significantly reduces insulin sensitivity (Buxton et al., 2010). In addition, restricting sleep for just 5 nights impairs the metabolism of glucose and lipids (Ness et.al., 2019). The aim of the current analysis is to determine whether postprandial salivary cortisol levels following an evening meal (dinner) are altered by prior sleep restriction conditions compared to a sleep replete (well-rested) condition. This study separately analyzed data from two similar sleep restriction studies. Each study investigated the effects of sleep restriction on metabolic response across three sleep conditions: baseline sleep, restricted sleep and recovery sleep. In Study 1, the protocol included three nights of baseline sleep (10 hours/ night), seven nights of sleep restriction (5 hours/ night) followed by one night of sleep recovery (10 hours/ night). In Study 2, the protocol included three nights of baseline sleep (10 hours/ night), five nights of sleep restriction (5 hours/ night) followed by two nights of sleep recovery (10 hours/ night). In Study 1, all meals were equicaloric with a controlled macronutrient composition regarded as a standard meal (STD). Study 1 had no high fat meals. Study 2 contained two identical high fat meals (HFD) for two nights of the study whereas standard meals (STD) were served the remaining days but differed in macronutrient composition. Hourly saliva samples were collected for cortisol assays to determine differences in pre-and postprandial levels for baseline and sleep restriction conditions. We hypothesized that, compared to baseline extended sleep, restricted sleep will result in an increased level of postprandial salivary (free) cortisol. Our results indicated a significant increase in pre- to postprandial salivary cortisol in the sleep restriction condition compared to baseline sleep in one pair of nights but not the other in Study 1, and no significant difference in pre- to postprandial cortisol in the sleep restriction compared to baseline sleep condition in Study 2. A mixed effect model indicated sleep condition as the significant driver of increased cortisol concentrations in Study 1, whereas in Study 2, the significant driver was meal type. Sleep restriction (5h/ night) for 1 week significantly increased pre to postprandial salivary cortisol following a dinner meal. Pre to postprandial salivary cortisol was also significantly increased after the consumption of a high fat meal regardless of sleep condition. These findings raise concerns regarding sleep restriction and diet and their role in metabolic dysregulation due to increased levels of cortisol.