A heart clock rhythm orchestra – a different tune at different times in the day

by Amal Mohamed Dameer on July 21, 2020 in Clocks in the Spotlight.

Have you ever had your blood pressure checked at the doctor’s? Did you assume your blood pressure stayed the same all day? It does not! It is in concert in a circadian rhythm orchestra with low base notes during the night and high peak notes during the day guided by a conductor in the brain called the master circadian clock. This master clock coordinates peripheral clocks, located in every cell and organ throughout the body, with environmental cues such as day/night, exercise, temperature, fasting and feeding. This prepares the body for anticipatory rest or activity by producing changes to heart rate, blood pressure, blood clotting ability, blood vessel function and cardiac hormones – the functional parts to pull the heartstrings to a heartbeat.


When the circadian clock concert’s harmony is repeatedly misaligned with behaviours and/or environment not appropriately timed to it – as happens in shift work or to a smaller degree in social jetlag – it can be injurious to health. Indeed, shift work can be an independent risk factor for heart disease due to repeated misalignment between cardiovascular system behaviours and the circadian clock. For example, non-dipping night-time blood pressure occurs, which is in disharmony to the circadian night-time music sheet for dipping blood pressure. This increases the risk for adverse cardiovascular events and hypertension in chronic shift workers. Experimentally induced heart attacks in mice recovered slower when there was a circadian disruption in light/dark cycles. Experiments tweaking clock genes showed impact on tolerance of the heart to deficient blood supply with some mutations making it worse and some making it better. The suggestion from research advances is that both light/dark cycles and internal clock disruption affect cardiovascular health. Shift-work circadian effects can be helped in workers with bright light use during shift and exposure to low light when they sleep during the day.

For the complete article, please see: https://srbr.org/a-heart-clock-rhythm-orchestra/

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