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

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.

Automated summary

The circadian system, controlled by clock genes, plays an important role in stroke outcomes. The circadian clock is present in the brain's suprachiasmatic nucleus and operates through molecular circadian clocks in neurons and other brain cells. Variations in the circadian cycle and clock genes can affect stroke occurrence and severity, with peak stroke occurring in the morning and worsening outcomes at midnight. Sleep blood pressure, influenced by the circadian rhythm, is a primary determinant of stroke risk.