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‘Covert strokes’ increase risk of dementia: report

Covert strokes occur five times more often than obvious strokes, and both are happening at a younger age, opening the door to more and earlier dementia, and sounding the alarm for an increased focus on prevention.

New data confirms a profound link between these two diseases of the brain. Having a stroke more than doubles the risk of developing dementia. Out of every 100 stroke patients without a past history of dementia, 16 are likely to develop dementia after their first or subsequent stroke. One in three Canadians will develop stroke, dementia, or both, according to the Heart and Stroke Foundation.

Stroke happens when blood stops flowing to parts of the brain, causing cells to die. Vascular cognitive impairment is also the result of blood vessel problems and results in a range of cognitive deficits, from relatively mild symptoms to vascular dementia. Both obvious clinical strokes and covert strokes – the type that happens when a small vessel becomes permanently blocked but there is no immediate outward physical damage – can lead to dementia.

“Stroke and dementia need to be studied together because in some ways they are one and the same,” says Dr. Andrew Demchuk, director, Calgary Stroke Program and Heart and Stroke Foundation spokesperson. “Stroke causes brain cells to die and this can precipitate dementia or worsen pre-existing dementia. There are different causes of dementia, and research now shows that stroke is a major contributor.”

According to a poll commissioned by the Heart and Stroke Foundation, Canadians’ awareness of both stroke and dementia is low. Less than half of Canadians know what a stroke is and less than one-third understand what dementia is and recognize the symptoms.

Uncovering covert strokes
Age is a risk factor for both stroke and dementia and as the population ages the actual number of strokes will rise, along with the number of people with dementia. Evidence is also showing that both are increasingly happening to younger people.

According to the most recent data from the Canadian Institute for Health Information (CIHI), 17 per cent of stroke patients were between the ages of 20 and 59. Similarly, according to new research that uses brain scan technology, covert strokes are also happening at an early age.

“About three per cent of Canadians in their 40s have evidence of a covert stroke. They can experience small strokes and they do not even realize it, and then it is too late as the damage is not reversible,” says Dr. Eric Smith, stroke neurologist, Calgary Stroke Program and Heart and Stroke Foundation spokesperson.

Currently one in 10 Canadians over 65 has dementia, and this increases to three in 10 over the age of 85. According to the Heart and Stroke Foundation poll*, more than one-quarter of Canadians mistakenly believe that dementia is a normal part of aging.

Dementia at an early age brings unique challenges, starting with difficulty getting a diagnosis, work-related and financial difficulties, as well as strain on relationships with spouses and children.

“My executive function and word-finding skills are damaged and this is permanent. I cannot multi-task the way I used to, and I have very little short-term memory so I have a white board in the kitchen and I write everything down. Everything also goes in my calendar. Thank goodness for technology; it is my lifeline,” says Susan Robertson, who was a full-time working mother when she had a stroke at 36.

Stroke – either a first stroke, subsequent stroke, TIA (mini-stroke) or covert stroke – can be prevented by managing vascular risk factors including high blood pressure and cholesterol and diabetes, as well as unhealthy behaviours such as tobacco use, physical inactivity and poor diet. The same is true for dementia. Dementia can be prevented, it can be delayed or its progression can be slowed by the same healthy behaviours. Physical activity and new learning – for example, learning a language or musical instrument – are particularly beneficial to good brain health.

High blood pressure is the number one modifiable risk factor for stroke yet according to the poll, less than one-quarter know it is a risk factor at all. When asked to identify risk factors, just over one-quarter named smoking, one-third identified poor diet, and less than one-fifth noted physical inactivity.

Nine in 10 Canadians have at least one risk factor for stroke and heart disease. This includes risk factors Canadians can do something about, and those they cannot change.

Risk factors Canadians can change:

• Know and control your blood pressure.
• Eat a healthy balanced diet that consists of a variety of natural/whole and minimally processed foods.
• Be physically active. Accumulate at least 150 minutes of moderate- to vigorous-intensity aerobic physical activity per week, in bouts of 10 minutes or more.
• Be smoke free.
• Manage diabetes.
• Limit alcohol. Women should limit themselves to no more than two drinks a day, to a weekly maximum of 10; and men to three drinks a day or a weekly maximum of 15.

Risk factors Canadians cannot change:

• having had a previous stroke or TIA (mini-stroke)
• family history of stroke or blood vessel problems
• age – the older you are, the higher your risk of stroke
• sex – until women reach menopause, they have a lower risk of stroke than men
• ethnicity – people of African or South Asian descent are more likely to have high blood pressure and diabetes.
• people of Indigenous heritage are reported to have higher incidence of high blood pressure and diabetes.

Visit heartandstroke.ca/strokereport for the full report.

*The poll with Canadians was conducted by Environics Research Group by telephone with 3,100 respondents 18 years and older, February 3–14, 2016.