The time dimension to stroke: Circadian effects on stroke outcomes and mechanisms

Nov 28, 2022Neurochemistry international

Daily timing affects stroke outcomes and underlying processes

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Abstract

Circadian rhythm variations may influence stroke outcomes, with peak stroke occurrences reported in the morning.

The master circadian clock in the brain is located in the suprachiasmatic nucleus (SCN).
Molecular circadian clocks in the SCN are regulated by specific genes, including Clock and Bmal1.
Negative feedback from genes like Per1-3 and Cry1-2 regulates these clock mechanisms.
Hypertension is a primary risk factor for stroke, with blood pressure typically dipping 15-20% during sleep.
Non-dippers, or those who do not exhibit this normal blood pressure pattern, may face increased stroke risk.
Stroke severity and poor outcomes are associated with variations in circadian timing, particularly at midnight.

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The circadian system is widely involved in the various pathological outcomes affected by time dimension changes. In the brain, the master circadian clock, also known as the "pacemaker," is present in the hypothalamus's suprachiasmatic nucleus (SCN). The SCN consists of molecular circadian clocks that operate in each neuron and other brain cells. These circadian mechanisms are controlled by the transcription and translation of specific genes such as the clock circadian regulator (Clock) and brain and muscle ARNT-Like 1 (Bmal1). Period (Per1-3) and cryptochrome (Cry1 and 2) negatively feedback and regulate the clock genes. Variations in the circadian cycle and these clock genes can affect stroke outcomes. Studies suggest that the peak stroke occurs in the morning after patients awaken from sleep, while stroke severity and poor outcomes worsen at midnight. The main risk factor associated with stroke is high blood pressure (hypertension). Blood pressure usually dips by 15-20% during sleep, but many hypertensives do not display this normal dipping pattern and are non-dippers. A sleep blood pressure is the primary determinant of stroke risk. This article discusses the possible mechanism associated with circadian rhythm and stroke outcomes.

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The time dimension to stroke: Circadian effects on stroke outcomes and mechanisms

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