Silent strokes carry risk of dementia

Silent strokes - which are hard to detect - can cause dementia and cognitive impairment, according to recent findings by the Memory Ageing and Cognition Centre at the National University Health System.

Its director, Associate Professor Christopher Chen, said that previous studies "had problems establishing a temporal link between silent stroke and symptoms as it was unclear when the silent stroke had occurred". So, only an association was made between the two.

But two studies, done between 2010 and 2014 by the centre, showed a "temporal link", he added in an interview last month.

In the first study, 649 people, picked randomly, underwent a brain scan. Results showed that six of them had suffered a recent stroke, though none of them had reported having one.

It was a result that was surprising and alarming, said Prof Chen, noting that the brain lesions have a span of only 10 days before they fade from the scanner's view. "If we catch one or two (at random), it is likely there are others," he said .

In the first study, 649 people, picked randomly, underwent a brain scan. Results showed that six of them had suffered a recent stroke, though none of them had reported having one.

The second study, done on about 1,000 patients, some of whom reported memory problems while others did not, showed it is three times likelier for the former group to have suffered silent strokes. "It supports this idea that silent strokes have a causal relationship (with) cognitive impairment," said Prof Chen.

He urged people, especially the elderly, to report signs of sudden confusion or dizziness to their family members or caregivers who must also, on their part, take care not to brush off these complaints as signs of ageing.

Symptoms of stroke can include slurred speech, drooping of the corner of the mouth, and one-sided weakness in the arms or legs. But "silent strokes do not present themselves in dramatic ways", said Prof Chen.

The medical community also needs to develop a standard procedure to help doctors detect silent strokes on scans, he said. "Currently, there are no guidelines. We actually have very good strategies to prevent stroke, and stroke is an under-recognised cause of dementia."

A version of this article appeared in the print edition of The Straits Times on January 01, 2016, with the headline 'Silent strokes carry risk of dementia'. Print Edition | Subscribe