Department Chair or Program Director
Bachelor of Science
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Morning and evening chronotypes (circadian preference) differ on several factors, such as stress response and sleep quality. Previous cardiovascular findings support the assumption that evening types exhibit a greater response to stress. Previous cortisol literature, in contrast, suggests that morning types have a greater response to stress. The two measures have not yet been investigated together in relation to chronotypes. The study explores differences in cardiac measures (heart rate (HR), heart rate variability (HRV)) as well as salivary cortisol in morning and evening types at baseline and under stress at different times of the day (7-11 AM or 4-7 PM). Students (n = 53) were pre-screened for chronotype preference. Participants provided salivary samples and completed a computerized mental arithmetic task while HR was recorded. Heart rate significantly increased from baseline during the task, and HRV significantly decreased. Evening types had significantly higher cortisol concentrations in the morning session, and significantly higher performance in the evening session. The interaction of chronotype and testing time did not reach significance for any of the dependent variables. General patterns partially support the idea that evening types may exhibit higher stress markers that could impair task performance.
Jacobs, Megan, "Physiological Differences in Stress Reactivity between Morning and Evening Chronotypes" (2019). Student Research Submissions. 281.