Impact of the human circadian system, exercise, and their interaction on cardiovascular function

• DOI: 10.1073/pnas.1006749107
• Publication Date: 2010-11-09T07:04:38Z
• Authors: Frank A. J. L. Sc...; Kun Hu; Heather Evoniuk; Erin E. Kelly; Atul Malhotra; Michael F. Hilton; Steven A. Shea
• Keywords: Adult; Male; Hemostasis; Likelihood Functions; 0303 health sciences; Time Factors; Hydrocortisone; Blood Pressure; Body Temperature; Circadian Rhythm; 3. Good health; 03 medical and health sciences; Catecholamines; Cardiovascular Diseases; Heart Rate; Humans; Female; Exercise

The risk of adverse cardiovascular events peaks in the morning (≈9:00 AM) with a secondary peak evening (≈8:00 PM) and trough at night. This pattern is generally believed to be caused by day/night distribution behavioral triggers, but it unknown whether endogenous circadian system contributes these daily fluctuations. Thus, we tested hypotheses that modulates autonomic, hemodynamic, hemostatic markers rest, stressors have different effects when they occur internal phases. Twelve healthy adults were each studied 240-h forced desynchrony protocol dim light while standardized rest exercise periods uniformly distributed across cycle. At there large variations plasma cortisol (peak-to-trough ≈85% mean, peaking phase corresponding ≈9:00 circulating catecholamines (epinephrine, ≈70%; norepinephrine, ≈35%, during biological day). ≈8:00 PM, was blood pressure cardiac vagal modulation. Sympathetic variables consistently lowest highest We detected no simple effect on hemostasis, although platelet aggregability had two peaks: ≈noon ≈11:00 PM. There modulation reactivity exercise, greatest withdrawal AM catecholamine numerous as well their resultant profiles could potentially contribute events.