Scientists have determined what time of day severe strokes occur more frequently

Scientists from the Carlos III National Research Center (CNIC, Spain) have established that the severity of ischemic stroke depends on the time of day it occurs: in the evening and nighttime hours, brain damage typically turns out to be more pronounced.

As reported by BAKU.WS with reference to the journal Circulation Research, a key role in this process is played by the circadian regulation of neutrophils - the most numerous cells of innate immunity that are the first to respond to a stroke. Experiments on mice and analysis of clinical data from more than 500 patients showed that in certain phases of the daily cycle, neutrophils transition to a more aggressive, pro-inflammatory state.

In the evening and nighttime, these cells more actively release extracellular traps - web-like structures made of DNA and proteins. Normally, they help the body fight infections, but during a stroke, their excess worsens microcirculation in the brain, contributes to the formation of microthrombi, reduces collateral blood flow, and increases tissue damage.

Conversely, in the morning hours, neutrophils behave less aggressively, which helps limit the affected area during a stroke. According to the study authors, these findings explain why patients with seemingly similar symptoms can have completely different outcomes.