There is a strong link between stroke and Alzheimer's disease — one which opens up new avenues of prevention and treatment, say researchers.
OTTAWA — For decades, doctors have diagnosed some patients with stroke and others with Alzheimer's disease, even though the vast majority of seniors suffer from a combination of each.
Now, a growing body of evidence suggests that, far from being diseases that develop independently of each other, stroke and Alzheimer's can overlap and speed up signs of dementia, says a leading Canadian brain researcher.
"These disorders cohabit, especially in an aging brain," Dr. Sandra Black told the Canadian Stroke Congress in Ottawa Tuesday. "Both of these conditions work against stroke recovery and hasten functional decline."
Some studies have estimated that up to half of all seniors with age-related dementia have both Alzheimer's and cardiovascular disease — the kind that can lead to a heart attack or stroke. In contrast, fewer than one-third have an exclusive Alzheimer's diagnosis, and only 10 per cent suffer strokes alone.
The findings suggest the same medications — and healthy habits — that are good for the heart can also be good for the head, said Black, a neurologist and researcher at Toronto's Sunnybrook Research Institute.
The relationship between stroke and Alzheimer's is still hotly debated by experts.
What's clear is that when the brain lacks a healthy flow of blood due to hardened or constricted vessels, it is less able to fight off the damage associated with dementia, said Black.
Indeed, the same risk factors that raise a person's chances of having a stroke — high cholesterol and blood pressure, excess weight, smoking, lack of exercise — also raise the risk of dementia.
Likewise, a brain injury caused by small, "silent" strokes can accelerate memory and learning problems in people who already are developing Alzheimer's, but show no symptoms.
In fact, it's the minor, difficult-to-detect strokes, rather than the signature plaques and tangles responsible for Alzheimer's, that speed cognitive decline and destroy a person's ability to reason, communicate and carry out normal day-to-day activities, said Black.
The most solid evidence comes from a study of 700 U.S. nuns, who were followed for many years. All the nuns had similar eating and exercise habits, and all agreed to allow their brains to be studied after death.
These autopsies confirmed a striking relationship between the presence in the brain of vascular disease and symptoms caused by damage related to Alzheimer's. What's more, the sisters with brain abnormalities characteristic of Alzheimer's were more likely to have symptoms of dementia if they also had strokes or clogged brain arteries.
Stroke and Alzheimer's are leading causes of disability among Canadian seniors and are responsible for $10.5 billion annually in direct health-care costs.
Each year, an estimated 50,000 Canadians suffer a stroke, and another 315,000 live with its effects. About 500,000 live with Alzheimer's, or a related dementia — a figure that's expected to double in the next two decades, according to the Alzheimer Society of Canada.
"Especially since (these diseases) will be epidemic in this century, we urgently need to understand how they develop, how some elders can resist them and how they interact so that we can better treat and prevent them," Black said.
Traditionally, stroke and Alzheimer's experts have resisted working together — a divide that is only starting to narrow. Having a better understanding of the relationship between the two diseases would help physicians treat the risk factors that could affect their progression, especially in people aged 75 and over, said Black.
Several studies have suggested that certain types of blood-pressure-lowering drugs, such as angiotensin receptor blockers (ARBS), might hold Alzheimer's at bay. Other studies have pointed to a link between Alzheimer's and cholesterol, raising the possibility that statins, the drugs that lower cholesterol, also might protect the brain.
"There's a lot of circumstantial evidence, but no one has done a face-to-face trial," said Black.
Controlling weight, eating low-fat and low-salt diets and keeping the brain active through reading, doing puzzles and learning new things also appear to protect the brain against dementia.
By far the most promising treatment, even for people who already show signs of dementia, is regular aerobic exercise.
Animal studies have found exercise can reduce the accumulation of the abnormal proteins that are a hallmark of Alzheimer's. An Australian study of patients with memory problems also showed that brisk walking for 150 minutes a week improved cognitive function.
Black's research team is conducting a study on the impact of exercise on patients with early Alzheimer's.
"I don't have an interaction with a patient and family now without talking about exercise, heart-healthy diet, salt — all that stuff," said Black.
Now, a growing body of evidence suggests that, far from being diseases that develop independently of each other, stroke and Alzheimer's can overlap and speed up signs of dementia, says a leading Canadian brain researcher.
"These disorders cohabit, especially in an aging brain," Dr. Sandra Black told the Canadian Stroke Congress in Ottawa Tuesday. "Both of these conditions work against stroke recovery and hasten functional decline."
Some studies have estimated that up to half of all seniors with age-related dementia have both Alzheimer's and cardiovascular disease — the kind that can lead to a heart attack or stroke. In contrast, fewer than one-third have an exclusive Alzheimer's diagnosis, and only 10 per cent suffer strokes alone.
The findings suggest the same medications — and healthy habits — that are good for the heart can also be good for the head, said Black, a neurologist and researcher at Toronto's Sunnybrook Research Institute.
The relationship between stroke and Alzheimer's is still hotly debated by experts.
What's clear is that when the brain lacks a healthy flow of blood due to hardened or constricted vessels, it is less able to fight off the damage associated with dementia, said Black.
Indeed, the same risk factors that raise a person's chances of having a stroke — high cholesterol and blood pressure, excess weight, smoking, lack of exercise — also raise the risk of dementia.
Likewise, a brain injury caused by small, "silent" strokes can accelerate memory and learning problems in people who already are developing Alzheimer's, but show no symptoms.
In fact, it's the minor, difficult-to-detect strokes, rather than the signature plaques and tangles responsible for Alzheimer's, that speed cognitive decline and destroy a person's ability to reason, communicate and carry out normal day-to-day activities, said Black.
The most solid evidence comes from a study of 700 U.S. nuns, who were followed for many years. All the nuns had similar eating and exercise habits, and all agreed to allow their brains to be studied after death.
These autopsies confirmed a striking relationship between the presence in the brain of vascular disease and symptoms caused by damage related to Alzheimer's. What's more, the sisters with brain abnormalities characteristic of Alzheimer's were more likely to have symptoms of dementia if they also had strokes or clogged brain arteries.
Stroke and Alzheimer's are leading causes of disability among Canadian seniors and are responsible for $10.5 billion annually in direct health-care costs.
Each year, an estimated 50,000 Canadians suffer a stroke, and another 315,000 live with its effects. About 500,000 live with Alzheimer's, or a related dementia — a figure that's expected to double in the next two decades, according to the Alzheimer Society of Canada.
"Especially since (these diseases) will be epidemic in this century, we urgently need to understand how they develop, how some elders can resist them and how they interact so that we can better treat and prevent them," Black said.
Traditionally, stroke and Alzheimer's experts have resisted working together — a divide that is only starting to narrow. Having a better understanding of the relationship between the two diseases would help physicians treat the risk factors that could affect their progression, especially in people aged 75 and over, said Black.
Several studies have suggested that certain types of blood-pressure-lowering drugs, such as angiotensin receptor blockers (ARBS), might hold Alzheimer's at bay. Other studies have pointed to a link between Alzheimer's and cholesterol, raising the possibility that statins, the drugs that lower cholesterol, also might protect the brain.
"There's a lot of circumstantial evidence, but no one has done a face-to-face trial," said Black.
Controlling weight, eating low-fat and low-salt diets and keeping the brain active through reading, doing puzzles and learning new things also appear to protect the brain against dementia.
By far the most promising treatment, even for people who already show signs of dementia, is regular aerobic exercise.
Animal studies have found exercise can reduce the accumulation of the abnormal proteins that are a hallmark of Alzheimer's. An Australian study of patients with memory problems also showed that brisk walking for 150 minutes a week improved cognitive function.
Black's research team is conducting a study on the impact of exercise on patients with early Alzheimer's.
"I don't have an interaction with a patient and family now without talking about exercise, heart-healthy diet, salt — all that stuff," said Black.
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