A new study suggests that people over 60 may be at risk of experiencing “silent” strokes, those which go unnoticed by their victim. But this variety of stroke may pose problems similar to a regular stroke, since it can also leave the individual with memory deficits and certain forms of dementia.

The research team from the University of New South Wales, led by Perminder Sachdev, tracked 477 participants (aged 60−64) for four years. Using Magnetic Resonance Imaging (MRI), they scanned the brains of the participants for signs of stroke. In 7.8% of the group there was evidence of stroke in the brain matter, although none of the patients had reported ever having had a stroke.

Four years later, the participants’ brains were scanned again, and the researchers found that an additional 1.6% had suffered from a silent stroke over this period.

What’s more, people with high blood pressure were 60% more likely than those with normal blood pressure to experience a silent stroke. Participants whose brains showed an anomaly called white matter hyperintensities (a type of damage that indicates that there is breakdown in the connection network of the brain) were five times as likely to experience a silent stroke as people without this pattern.

Sachdev speculates that silent strokes “probably have a cumulative effect. If they are very small then the brain has enough reserves to be able to cope with them and not show any abnormalities in function. But as they are increasing then the brain's reserve is depleted and you start seeing abnormalities.” He points out that other symptoms of silent stroke are slowing of processing speed, a decrease in detailed memory, and problems with motor movements.

He suggests that seniors have their blood pressure checked at regular intervals, and begin working to bring it down if it is too high. "We see blood pressure as one of the risk factors and it shouldn't be, because high blood pressure is entirely treatable."