Date of Award

Fall 10-1-2016

Degree Type


Degree Name

MS Microbiology




Roberta Moldow, Ph.D.

Committee Member

Jane Ko, Ph.D.

Committee Member

Heping Zhou, Ph.D.

Committee Member

Angela V. Klaus, Ph.D.


circadian rhythm, salivary cortisol, cognition, sleep-wake cycle, hypothalamic-pituitary-adrenal axis (HPA)


Cortisol is a salivary marker for the hypothalamic-pituitary-adrenal axis (HPA) component of the stress response. The activity of the HPA demonstrates a circadian rhythm. It is well known that sleep deprivation increases cortisol concentrations. In this study, we looked at the effect of an increase of one-hour sleep for one month on the circadian rhythm of the HPA.

Eight college subjects (n=8) collected saliva during their normal sleep wake cycle every 4 hours for 24 hours. Saliva collections were repeated after a month of increase of sleep by 1-hour. The subjects also completed demographic forms that asked for age, sex, time of last meal, smoker, caffeine consumption, time going to sleep, and time waking up. ELISA kits were used to analyze cortisol concentrations.

Salivary cortisol concentrations demonstrated a circadian rhythm, which revealed a significant peak at 0800h, which is consistent with the literature. The study shows that the total concentrations of salivary cortisol secreted over 24 hours as calculated by area under the curve (AUC) reveals that there is a significant decrease with increased sleep.