Nikhil Prasad Fact checked by:Thailand Medical News Team Jan 14, 2026 4 hours, 40 minutes ago
Medical News: A new study from Croatia is raising alarms about an unexpected danger lurking behind the familiar winter flu. Researchers from the Department of Infectious Diseases and the Department of Neurology at University Hospital of Split, the University of Split School of Medicine, the Faculty of Health Sciences at the University of Split, and the Public Health Institute of Split and Dalmatian County have found that even mild influenza could temporarily weaken how well blood circulates in the brain.
Mild flu quietly weakens blood flow in the brain, a new study warns
The finding emerged after a close look at 92 adults aged 28 to 62, half of whom had confirmed influenza while the other half were healthy volunteers. Using a non-invasive ultrasound method called transcranial Doppler, the investigators measured the blood flow through a major brain artery during normal breathing and after patients held their breath.
This technique lets scientists calculate something called the breath-holding index, a key indicator of how responsive blood vessels are to changes in the body’s demands.
What The Scientists Discovered
According to this
Medical News report, the flu group performed significantly worse on nearly every measurement:
• Blood flow was slower at rest than in healthy people
• Blood flow rose less sharply during breath-holding, meaning vessels could not widen properly
• Breath-holding time was shorter, likely due to lung irritation
• Overall cerebrovascular reactivity was reduced by half
Researchers described this reduced responsiveness as a sign of impaired cerebrovascular reactivity, a condition linked to higher future stroke risk. Detailed figures show dramatic contrasts. The flu group recorded a median breath-holding index of only 0.47, compared to 0.99 among healthy controls. Flow velocity also rose far less after breath-holding, showing the brain’s circulation was struggling to adapt.
Recovery Offers Hope
Importantly, when the influenza sufferers returned three months later, their brains worked better. Blood flow responses improved markedly and the breath-holding index nearly doubled to 0.91, approaching normal levels. However, resting blood flow had not completely caught up, suggesting deeper recovery may take longer.
Participants also reported feeling healthier and exercising more than during their illness, offering another clue that the body rebounds gradually after infection.
Why This Matters
Doctors have long suspected infections could nudge people toward strokes and heart attacks, but this study may be the first to show a real-time functional impact on brain vessels in uncomplicated flu cases. The work suggests that inflammation triggered by influenza temporarily stiffens and disrupts the blood vessel lining, limiting the brain&rs
quo;s ability to compensate during stress.
The conclusions are sobering. Influenza may not just be a respiratory nuisance. Even in adults without high blood pressure, diabetes or obesity, the virus briefly weakens the brain’s protective circulation system and may contribute to stroke risk in the weeks after infection. More studies are needed to determine whether vaccination or antiviral treatment can guard against these invisible changes.
Final Conclusion
This study shines a light on influenza as more than a lung illness. By showing measurable reductions in the brain’s capacity to boost blood flow, the findings reveal a hidden vulnerability that persists after symptoms fade. Although most patients recover this capacity within months, the temporary weakness may help explain the uptick in strokes seen during flu season. The research reinforces the importance of preventing influenza and treating it seriously, as its harm may reach farther than many realize.
The study findings were published in the peer reviewed journal: PLOS One.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0340768
For the latest on influenza infections, keep on logging to Thailand
Medical News.
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https://www.thailandmedical.news/articles/influenza-or-flu
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