Undetected strokes increase dementia risk

At the recent Canadian Stroke Congress in Ottawa, Dr. Sandra Black, director of Sunnybrook's brain sciences research program, presented an overview on the relationship between vascular brain disease and Alzheimer's disease, including evidence that so-called silent strokes increase the risk of dementia.

"Previous brain imaging studies in other countries of people aged 65 and older show that 95 per cent have brain small vessel disease seen as white spots and patches on magnetic resonance images," says Dr. Black, Brill Chair in Neurology at University of Toronto. " Longitudinal follow up has shown that this other type of small vessel disease also increases risk for clinical stroke events, depression, falls, and Alzheimer's dementia."

These studies have shown that a quarter of healthy senior volunteers living in the community have evidence of small silent strokes. Even in middle-aged people (average age 60), this number may be as high as 14 per cent, according to preliminary results of the Canadian PURE MIND study, which provides the first such information in Canada.

"Sixty-five per cent of stroke patients experience difficulty with thinking, memory, goal setting and motivation after a stroke, and 20 to 30 per cent become clinically demented within three months post-stroke," adds Dr. Black.

While a major stroke event can result in the sudden loss of thinking and walking abilities, brain small vessel disease can also have the same effects over a more gradual period of time.

"The time is now for the brain to be the top priority for Canada's health research community," says Dr. Black. In the next 20 years the number of people with dementia and Alzheimer's disease is expected to reach more than one million in Canada alone, increasing ten-fold the current health care costs of $15 billion per year, she says.

In the meantime, there are important counter measures people can take to delay and prevent these devastating diseases. This is because stroke and Alzheimer's share the same vascular risk factors, such as high blood pressure, obesity, diabetes, and high cholesterol. Stopping smoking, losing weight and regular aerobic exercise may delay onset of cognitive decline and dependency in daily activities.