Mind the connection: Preventing stroke and dementia

-- Submitted by Dr. Patrice Lindsay and Stephanie Lawrence, Heart and Stroke Foundation

Stroke and dementia — it’s all in our heads

Stroke and dementia have much in common. Both are diseases of the brain. Stroke happens when the blood flow to the brain is interrupted and cells die as a result. Vascular dementia is often a further result of stroke damage, from either larger strokes or smaller ones accumulating over time.

Patients with stroke and dementia often share the same vascular risk factors including high blood pressure, high cholesterol and diabetes, as well as unhealthy behaviours such as tobacco use, physical inactivity and poor diet.

Both are age-related diseases — the older we get, the greater the chance of having a stroke and developing dementia. Yet, at the same time, both are increasing among younger people.  

Vascular cognitive impairment (VCI) occurs when blood vessel problems prevent brain cells from getting the oxygen they need, causing them to die. It is a syndrome where at least one cognitive domain is impaired, for example, attention, memory, language, perception or executive function. VCI encompasses a range of cognitive deficits, from relatively mild to vascular dementia, the most severe form. VCI is usually the result of stroke.

There are 62,000 strokes in Canada each year and 405,000 Canadians are living with the effects of stroke. Having a stroke more than doubles someone’s risk of developing dementia.Hundreds of thousands of Canadians over the age of 65 have dementia.

All strokes are not the same

A stroke happens when blood stops flowing to any part of the brain. This interruption causes damage to the surrounding brain cells which cannot be repaired or replaced; 1.9 million brain cells die every minute after stroke. Strokes can be large or small, and the effects of stroke depend on the part of the brain and the extent of damage.

Ischemic stroke is the most common form of stroke, caused by a blood clot.  
Hemorrhagic stroke occurs when a blood vessel ruptures, causing bleeding in or around the brain.

A transient ischemic attack (TIA) is sometimes referred to as a mini-stroke. TIAs are caused by a small clot that briefly blocks an artery and stops blood flow to part of the brain for a short period. Acute TIA symptoms might last only a few minutes; most are resolved within an hour and all symptoms are gone within 24 hours. However TIAs are an important warning that a more serious stroke may occur — 20 per cent of people who experience one will have a bigger stroke within three months, with the majority happening in the first few days after the TIA. Anyone who experiences a TIA should seek medical help immediately.

A covert stroke occurs when a small vessel becomes permanently blocked. Although cells around the affected area die, there is no obvious immediate outward physical damage or functional impact. Covert strokes do not affect muscle or motor skills — there is no paralysis, slurred speech or face droop.

Most people who have covert strokes don’t know it, as the name implies.

“They happen to people who don’t have a history of stroke, but it’s important for people to realize that covert strokes can have subtle symptoms for which they should seek attention from their doctor. In particular, the importance of covert strokes seems to be on changes in memory as people get older, which can interfere with their daily activities,” says Dr. Eric Smith, Stroke Neurologist, Calgary Stroke Program.

Unlike obvious (or clinical) strokes which happen in the brain's grey matter that controls specific functions, including movement, speech, and vision, covert strokes usually involve white matter which act as pathways in the brain connecting various grey matter regions. Covert strokes weaken connections necessary for what is often referred to as executive function. This includes processing information, remembering recent events, word-finding, finding your way around, multi-tasking, problem-solving, planning, decision-making and reasoning.

What dementia does

Dementia is not one specific disease; it is a combination of symptoms that has many different causes, and symptoms can range from mild cognitive impairment to severe dementia. Alzheimer’s disease is one common cause of dementia, but vascular cognitive impairment, usually caused by strokes, is almost as common. Alzheimer's disease and vascular dementia often occur together. This is referred to as “mixed dementia.”

“Dementia is a major problem in Canada, especially with an aging population. It refers to memory and thinking problems that prevent people from doing the things that used to be routine for them,” says Dr. Smith.

Dementia erodes your ability to remember things, find words, solve problems and follow directions all of which interfere with daily activities. In its mildest form dementia causes difficulties with day-to-day activities like shopping, managing money, driving, housework, and taking medications. More severe dementia causes difficulty performing even basic tasks such as getting dressed and bathing. It can come on suddenly but in some cases — especially with vascular or mixed dementia — its appearance can happen slowly. Effects can also happen in stages, where abilities deteriorate and then level off for a time before declining again.

The accompanying burden to the Canadian economy is high. Today, the combined direct (medical) and indirect (lost earnings) costs of dementia total $33 billion a year. If nothing changes, this number will climb to $293 billion a year by 2040.

The link between stroke and dementia

Stroke is now understood to be a powerful predictor of dementia — one-third of dementia risk can be attributed to stroke. The strokes that cause dementia can be large or small, and the results can be identified immediately or develop gradually over years.

“The amount of dementia does not always directly reflect the severity of the stroke,” says Dr. Smith. “A big stroke may not cause much dementia or any — depending on where it hits. On the other hand, tiny strokes can cause a lot of dementia.”

More stroke = more dementia

Evidence continues to reinforce the connection between stroke and dementia — the incidence for each increases the risk for the other. Research confirms this disturbing association: 10 per cent of stroke patients are diagnosed as having prior dementia, and an additional 10 per cent develop dementia after their first stroke. Having recurrent strokes further increases the chances of cognitive decline. More than one-third of patients develop dementia after a second stroke.

According to estimates based on the most current Canadian data, of every 100 stroke patients without a past history of dementia, 16 are likely to develop dementia after their first or recurrent stroke.

One in three Canadians will develop stroke, dementia, or both.

Uncovering covert strokes

Around the world, evidence has emerged over the last few years that strokes among younger people are increasing. In Canada all stroke risk factors for younger adults are on the rise. Alarmingly, according to most recent CIHI data, 17 per cent of hospital admissions for stroke and TIA were for patients between the ages of 20 and 59.

According to new research, covert strokes can also happen at an early age. This is difficult information to collect given that covert strokes go largely unrecognized and undiagnosed.

Brain scan technology can identify changes to the brain that indicate someone might have had covert strokes. Experts are now realizing that these small and hidden strokes are unfortunately helping lay the groundwork for vascular dementia.

“About three per cent of Canadians in their 40s have evidence of a covert stroke. This is especially true of people who are in poorer health because of vascular risk factors. 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. Smith.

This may not be such a surprising statistic given that covert strokes occur five times as often as obvious (or clinical) strokes. The incidence increases as people age; almost 20 per cent of 70-year-olds have experienced covert strokes.

The good news is that once evidence of covert strokes is uncovered, the focus can be put on a patient’s blood vessel health to ensure that vascular risk factors are being managed to prevent further damage including a bigger stroke.

Stroke at an earlier age brings with it the threat of dementia at an earlier age. Currently one in 10 Canadians over 65 has dementia, and this increases to three in 10 over the age of 85. The number of people with vascular dementia doubles every five years after age 65.

Diagnosing dementia in people under 65 can be difficult and can take years as family doctors rule out other causes for changes in behaviour. Health professionals should start considering stroke and dementia when diagnosing younger patients.

“The first signs of early-onset dementia can be work related,” says Dr. Theresa Green, Associate Professor, Faculty of Nursing, University of Calgary. “There can be a decline in performance but nobody knows why.”

Dementia in middle age can result in new challenges that older patients do not face. Those who are still of working age can experience challenges at work or face financial difficulties if they have to leave their jobs. Their spouses can feel overwhelmed with new responsibilities as caregivers and increased responsibilities taking care of children and teenagers, and older parents, as well as running a household

“Early dementia can be unravelling for the entire family,” says Dr. Green. “Children and teenagers tend to dissociate from a parent with dementia, and the whole dynamic of a marriage can change.”

People in their 40s and 50s tend to be involved in a broader range of activities that they want to continue compared with more elderly patients. Their families also require support to cope with their new situation. Unfortunately support and services appropriate for these specific patients and their caregivers are lacking.

The cost in lives

According to the latest CIHI data, patients hospitalized for stroke and who also have dementia are at a much greater risk of dying than those without dementia. The mortality rate is just over 20 per cent for patients with both stroke and dementia, as compared with 13 per cent for those with just stroke.

Almost half of stroke patients (45 per cent) without dementia are sent home from hospital without the need for additional support services. This is in striking contrast to only 14 per cent of those with dementia — many fewer because they are not able to manage without support. It is no surprise then that 29 per cent of stroke patients with dementia are sent to long-term care instead of returning home, compared with just five per cent of stroke-only patients.

Even in hospital, once out of acute care, stroke patients with dementia require more complex care — at more than double the rate of those without dementia.

On average, people with vascular dementia live for five years, with a shorter lifespan than the general population and those who have Alzheimer’s.  

The consequences of dementia stretch beyond the significant challenges individuals face navigating their everyday lives. Depression and vascular cognitive impairment — whether milder forms or more severe dementia — are related; — they may both be caused by something called white matter disease, and are often seen in stroke patients. Depression can also be the result of trying to cope and adjust to the many changes and loss after a stroke. Canadian Stroke Best Practice Recommendations state that post-stroke patients with suspected cognitive impairment should be screened for depression.  

Age is still a significant risk factor

In most age groups, rates of stroke have been declining, which is welcome news. “The age-standardized risk for dementia has also decreased and we suspect much of the decline is linked to better vascular risk factor management,” says Dr. Smith.

Unfortunately the somewhat lower rates of stroke and dementia at any given age is more than matched by the dramatically increasing number of older Canadians; age is a risk factor for both stroke and dementia. As the population ages the actual numbers of strokes will rise, along with the number of people who develop dementia. Clinicians are already seeing more strokes and more dementia, and are treating more patients.

Preventing stroke prevents dementia

If having stroke increases the risk of developing dementia, it follows that preventing stroke also prevents dementia and vascular cognitive impairment. It is never too early to prevent both stroke and dementia and it is never too late to reduce risk.

“Reducing stroke risk protects your brain. Healthy living is about dementia too. Everything you do to protect your body protects your brain,” says Dr. Smith.

Stroke — either a first stroke, subsequent stroke, TIA or covert stroke — can be prevented by managing vascular risk factors. The same is true for dementia. Dementia can be prevented, it can be delayed or its progression can be slowed by the same approaches.

Resources

Resources for Canadians

  • Learn the signs of stroke and act FAST by calling 9-1-1 immediately. Visit http://heartandstroke.ca/FAST
  • Know and manage your stroke risk factors. Take the Heart&Stroke Risk Assessment at http://heartandstroke.ca/ehealth
  • Take control of your blood pressure with the Heart&Stroke Blood Pressure Action Plan at http://heartandstroke.ca/ehealth.
  • Use the Heart and Stroke Foundation patient resources available at http://www.heartandstroke.com/site/c.ikIQLcMWJtE/b.3483933/k.CD67/Stroke...
    • Your Stroke Journey: A Guide for People Living with Stroke is a comprehensive guide to help stroke survivors and their families understand the effects of stroke and manage their recovery.
    • Taking Charge of your Stroke Recovery: A Survivor’s Guide to the Canadian Stroke Best Practice Recommendations is a resource for stroke survivors and their families that describes key recommendations for stroke care.
    • Post-stroke checklist for clinicians and patients is an easy to use guide to ensure important aspects of stroke prevention and follow-up are addressed.

Resources for healthcare providers
Canadian Stroke Best Practice Recommendations provide comprehensive guidelines for healthcare professionals working with stroke patients and their families, and patient and professional education resources have also been developed. http://strokebestpractices.ca

Get the full report at http://heartandstroke.ca/strokereport,

Find out how to recognize the signs of stroke at http://heartandstroke.ca/FAST.