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[Relationship between circadian rhythms and blood pressure and the pathogenesis of cerebrovascular insufficiency]
Insights
Cerebrovascular accidents peak in the morning for most individuals due to autonomic nervous system changes. However, hypertension leads to a more even distribution of these events throughout the day.
Area of Science:
- Neurology
- Cardiology
- Physiology
Context:
- Cerebrovascular accidents (CVAs) exhibit diurnal variations, with higher incidence in the morning.
- Hypertension influences the temporal distribution of CVAs.
- Autonomic nervous system activity and cardiac arrhythmias are implicated in CVA timing.
Purpose:
- To investigate the diurnal patterns of cerebrovascular accidents.
- To explore the role of hypertension in altering CVA timing.
- To elucidate the physiological mechanisms underlying CVA occurrence throughout the day.
Summary:
- Non-embolic CVAs are more frequent in the morning, linked to nocturnal autonomic nervous system effects causing reduced microcirculation autoregulation.
- Embolic CVAs may be associated with heart arrhythmias during waking hours.
- Hypertensive individuals show a uniform CVA distribution, possibly due to restricted microcirculation and constant cerebro-vascular resistance offering paradoxical protection.
Impact:
- Understanding diurnal CVA patterns can inform preventative strategies and chronotherapy.
- Identifying risk factors associated with specific timing may improve patient outcomes.
- This research highlights the complex interplay between blood pressure, autonomic function, and cerebrovascular events.
Abstract:
Cerebrovascular accidents occur more frequently during the morning, less frequently during the night, whether due to thrombosis or embolism. In cases with hypertension, however, there have been noted a more uniform distribution of these complications throughout the day. The preponderance in the morning of the number of accidents in non-embolic subjects, depends probably on the state of the autonomic nervous system during the night, which gives rise to a dilated and hypotonic microcirculation. Autoregulation is, in this way, reduced and the physiological increase in blood pressure during the morning may induce a break through of autoregulation. In embolic subjects, on the other hand, an important role may be played by heart arrhythmias which occur usually during the waking hours. In hypertensives, the microcirculatory bed is restricted and cerebro-vascular resistance relatively constant. The brain, paradoxically, is thus better defended against any moderate increase in blood pressure and fluctuations in blood pressure throughout 24 hours, which may leave cerebral autoregulation unchanged, which probably explains the more uniform distribution of cerebro-vascular accidents throughout the 24 hour period.