Up to three million people over the age of 65 each year could be experiencing "silent strokes" after surgery, research published in the Lancet medical journal suggests.
Covert strokes, which are not obvious except on a brain scan, are more common than strokes that swiftly bring about visible symptoms, Canadian researchers found.
They found that one in 14 post-operative patients had a silent stroke when they surveyed more than 1,000 people in North and South America, Asia, New Zealand, and Europe.
This suggests up to three million people over the age of 65 could be experiencing silent strokes every year globally, according to the study led by the Population Health Research Institute of Hamilton Health Sciences and McMaster University in Hamilton, Ontario, Canada.
Dr PJ Devereaux, co-principal investigator of the NeuroVISION study, said: "We've found that 'silent' covert strokes are actually more common than overt strokes in people aged 65 or older who have surgery."
Those who had a silent stroke after surgery were 13 per cent more likely to experience cognitive decline, delirium, overt stroke or a "mini stroke", caused by a temporary disruption in the blood supply to part of the brain, within one year.
Dr Brian Rowe, scientific director of the Institute of Circulatory and Respiratory Health, Canadian Institutes of Health Research (CIHR), said: The NeuroVISION Study provides important insights into the development of vascular brain injury after surgery, and adds to the mounting evidence of the importance of vascular health on cognitive decline.
Australian Associated Press