Sydney, July 31 - Beware of the 'silent' stroke that doesn't leave any outward symptoms, but causes brain damage. It afflicts people over 60, especially those with high blood pressure.

'These strokes are not truly silent, because they have been linked to memory and thinking problems and are a possible cause of a type of dementia,' said study author Perminder Sachdev, neuropsychiatry professor at the University of New South Wales (UNSW).

'High blood pressure (BP) is very treatable, so this may be a strong target for preventing vascular disease,' said Sachdev, who did his MBBS and MD in 1978 and 1981 respectively from the All India Institute of Medical Sciences in New Delhi.

The study involved 477 people aged between 60 to 64 years who were followed for four years.

At the beginning, 7.