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Circadian variation in the timing of stroke onset: a meta-analysis
1Department of Preventive Medicine, Rush Medical College of Rush University, and Rush-Presbyterian-St Luke's Medical Center, Chicago, Ill 60612, USA.
Insights
Stroke risk shows a clear circadian rhythm, with a significant increase in onset between 6 AM and noon. This morning peak affects all stroke subtypes, contradicting previous assumptions of no daily variation.
Area of Science:
- Neurology
- Circadian Biology
- Epidemiology
Background:
- Cardiovascular events like myocardial infarction exhibit circadian patterns.
- Previous research on stroke circadian variation yielded conflicting results, particularly for hemorrhagic stroke.
Purpose of the Study:
- To investigate the circadian timing of stroke onset.
- To determine if stroke subtypes demonstrate specific daily patterns.
Main Methods:
- A meta-analysis of 31 studies involving 11,816 stroke cases.
- Analysis of stroke onset times, subdivided by stroke type.
- Statistical methods to assess circadian variation, with even distribution for unspecified onset times.
Main Results:
- All stroke subtypes showed significant circadian variation in onset (P<0.001).
- A 49% increase in stroke risk was observed between 6 AM and noon.
- Risk was lower during midnight to 6 AM, with increased morning risk for ischemic, hemorrhagic, and transient ischemic attacks.
Conclusions:
- Stroke onset follows a distinct circadian pattern.
- A significantly higher risk of stroke occurs in the morning hours.
- These findings support the existence of daily biological rhythms influencing stroke occurrence.
Background And Purpose:
Acute myocardial infarction and sudden death display a circadian rhythm, with a higher risk between 6 AM and noon. Some reports suggest that stroke does not follow such a circadian variation and that hemorrhagic stroke occurs more often during the evening.
Methods:
A meta-analysis of 31 publications reporting the circadian timing of 11,816 strokes was performed, subdividing (when possible) by the type of stroke, according to the time of onset of symptoms. When precise timing was not given, strokes were distributed evenly (that is, biasing toward the null hypothesis of lack of circadian variation).
Results:
All subtypes of strokes displayed a significant (P<0.001) circadian variation in time of onset, whether divided into 3-, 4-, or 6-hour time periods. There was a 49% increase (95% confidence interval, 44% to 55%) in stroke of all types between 6 AM and noon (compared with expectations if no circadian variation was present), which is a 79% (95% confidence interval, 72% to 87%) increase over the normalized risk of the other 18 hours of the day. There were 29% fewer strokes between midnight and 6 AM, a 35% decrease compared with the other 18 hours of the day. All three subtypes of stroke had a significantly higher risk between 6 AM and noon (55% for 8250 ischemic strokes; 34% for 1801 hemorrhagic strokes, and 50% for 405 transient ischemic attacks).
Conclusions:
These data support the presence of a circadian pattern in the onset of stroke, with a significantly higher risk in the morning.