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The impact of the circadian timing system on cardiovascular and metabolic function
Christopher J Morris1, Jessica N Yang2, Frank A J L Scheer1
1Division of Sleep Medicine, Brigham and Women's Hospital, Boston, MA, USA; Division of Sleep Medicine, Harvard Medical School, Boston, MA, USA.
Insights
Cardiovascular events peak in the morning, influenced by the body's internal clock. Circadian misalignment in shift workers increases their risk for heart disease, obesity, and diabetes.
Area of Science:
- Chronobiology
- Cardiovascular Physiology
- Metabolic Health
Background:
- Adverse cardiovascular events exhibit a morning peak (6 AM-noon).
- Shift work is linked to increased cardiovascular disease, obesity, and diabetes.
- The body's internal circadian timing system influences cardiovascular risk markers.
Purpose of the Study:
- To investigate the role of the circadian timing system in the morning peak of cardiovascular events.
- To explore the impact of circadian misalignment on cardiovascular and metabolic health, particularly in shift workers.
Main Methods:
- Review of epidemiological data on cardiovascular event timing.
- Analysis of how the endogenous circadian system modulates cardiovascular risk factors and stress responses.
- Examination of studies on circadian misalignment and simulated night work effects on cardiovascular and metabolic function.
Main Results:
- Cardiovascular risk markers (e.g., cortisol, platelet activation) and stress responses (e.g., epinephrine) are highest or most unfavorable during the morning hours.
- Circadian misalignment and simulated night work negatively affect cardiovascular and metabolic function.
- The interaction between the circadian system and external stressors may explain the morning cardiovascular event peak.
Conclusions:
- The circadian timing system and its interplay with cardiovascular stressors contribute to the morning peak in adverse cardiovascular events.
- Circadian misalignment in shift workers is a significant factor in their elevated risk for cardiometabolic diseases.
Abstract:
Epidemiological studies show that adverse cardiovascular events peak in the morning (i.e., between 6 AM and noon) and that shift work is associated with cardiovascular disease, obesity, and diabetes. The endogenous circadian timing system modulates certain cardiovascular risk markers to be highest (e.g., cortisol, nonlinear dynamic heart rate control, and platelet activation) or to respond most unfavorably to stressors such as exercise (e.g., epinephrine, norepinephrine, and vagal cardiac modulation) at an internal body time corresponding to the time of day when adverse cardiovascular events most likely occur. This indicates that the circadian timing system and its interaction with external cardiovascular stressors (e.g., physical activity) could contribute to the morning peak in adverse cardiovascular events. Moreover, circadian misalignment and simulated night work have adverse effects on cardiovascular and metabolic function. This suggests that misalignment between the behavioral cycle and the circadian timing system in shift workers contributes to that population's increased risk for cardiometabolic disease.
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