0044 Impact Of Cognitive Stress, Circadian System And Their Interaction On Human Cardiovascular Function

• Published in: Sleep (New York, N.Y.) N.Y.), 2018-04, Vol.41 (suppl_1), p.A18-A18
• Main Authors: Chellappa, S, Hu, K, Shea, S, Scheer, F
• Format: Article
• Language: English
• Subjects: Behavior; Biological clocks; Circadian rhythm; Heart rate
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsy061.043

Abstract Introduction Maximum risk for adverse cardiovascular events (e.g., myocardial infarction, stroke) occurs in the morning hours (~6AM-12PM). These time-of-day variations may be due to effects of daily rhythms in behaviors or the circadian system on cardiovascular function. Cognitive stress is one behavioral factor that may contribute to the morning peak in adverse cardiovascular events. However, if the circadian system influences the cardiovascular response to human cognitive stress unknown. Methods Twelve healthy adults underwent a 240-h forced desynchrony protocol with all behaviors scheduled on 20-h recurring cycles to assess circadian function independent from environmental/behavioral effects (e.g., sleep/wake cycle). Cognitive stress was induced by a serial addition task. Outcomes of cardiovascular function included hemodynamic function [heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP)], circulating catecholamines (epinephrine and norepinephrine), sympathovagal balance (LF/HF) and cardiac vagal modulation [root square mean (RMSSD) and pNN50)]. Results Cognitive stress increased hemodynamic function (HR ~7%; SBP, DBP ~5%) and sympathovagal balance (LF/HF ratio ~25%), while it decreased cardiac vagal modulation (RMSSD, pnn50 ~50%). Significant circadian variations were observed in cardiovascular function, with peaks at circadian phases corresponding to ~12-4PM for heart rate and epinephrine, ~22PM for blood pressure, ~4AM for cardiac vagal modulation, and ~8AM for sympathovagal balance. No significant interactions occurred for cognitive stress and circadian phase. Performance (subjective ratings and task accuracy) and stress (subjective ratings and cortisol levels) did not predict time-of-day fluctuations on cardiovascular function, suggesting a cognitive stress effect per se. Conclusion Our data show that cognitive stress and the endogenous circadian system have additive effects on human cardiovascular function. Therefore, if cognitive stress occurs in the biological morning, its additive effects with the circadian system on cardiovascular function (e.g., sympathovagal balance and cardiac vagal tone) may put individuals at increased risk during those vulnerable hours. Support (If Any) NIH-R01-HL76409; NIH-K24-HL076446 (SAS); NIH-P30-HL101299 (FAJLS); NCRR-GCRC-M01-RR02635.