People with cognitive impairment are significantly more likely to have a stroke, with a 39% increased risk, than people with normal cognitive function, according to a new study published in CMAJ (Canadian Medical Association Journal).
“Given the projected substantial rise in the number of older people around the world, prevalence rates of cognitive impairment and stroke are expected to soar over the next several decades, especially in high-income countries,” writes Dr. Bruce Ovbiagele, Chair of the Department of Neurology, Medical University of South Carolina, Charleston, South Carolina, with coauthors.
Cognitive impairment and stroke are major contributors to disability, and stroke is the second leading cause of death world-wide. Although stroke is linked to the development and worsening of cognitive impairment, it is not known whether the reverse is true. Previous studies that have looked at the link between cognitive impairment and subsequent stroke have been inconsistent in their findings.
The study in CMAJ, by researchers in the United States, Taiwan and South Korea, analyzed data from 18 studies of 121 879 people with cognitive impairment, of whom 7799 later had strokes. Most of the included studies were conducted in North America or Europe.
The researchers observed a significantly higher rate of stroke in people with cognitive impairment than in people with normal cognitive function.
“We found that the risk of future stroke was 39% higher among patients with cognitive impairment at baseline than among those with normal cognitive function at baseline,” write the authors. “This risk increased to 64% when a broadly adopted definition of cognitive impairment was used.”
Stroke symptoms often include cognitive impairment. Cognitive deficits may manifest in different ways including confusion, memory problems, decreased mental ability, impulsiveness, distractibility, impaired judgement, executive dysfunction, and agnosognosia (patient’s inability to recognize his/her impairment).
Confusion - The stroke victim may appear disoriented, have short term memory loss, or demonstrate bizarre or unusual behavior. Confused patients will have problems sustaining a meaningful conversation. Sometimes a patient may appear confused but actually have aphasia which is a speech disorder where the patient can have difficulty producing or comprehending speech. See the aphasia page for more information.
Memory Problems - Memory loss after a stroke is not uncommon. It can present as an inability to learn and recall new information or remember and retrieve long term memory. Sometimes the loss is subtle, and a caregiver may not notice memory problems until the patient attempts more complicated activities of daily living. Ideas to help the stroke patient with memory deficits, include establishing a standard daily routine, keeping frequently used items in a designated place, and making a memory notebook for important information.
Impulsiveness - The impulsive stroke patient will not think before acting and has trouble with impulse control. Impulsiveness is most common in patients that have experienced a frontal lobe or right brain stroke. Safety may be compromised because the patient may try to do activities that he or she is incapable of doing (i.e. driving, cooking, walking without assistance, etc.) Caregivers may think that their loved one is trying to maintain independence when in fact the patient’s impulse control has been impaired. Impulsiveness can also cause inappropriate behavior responses such as sudden anger, yelling, crying or rude remarks.
Blockage of blood vessels in the brain (brain infarcts), atherosclerosis, inflammation and other vascular conditions are associated with a higher risk of stroke and cognitive impairment and may contribute to the increased risk.
“Cognitive impairment should be more broadly recognized as a possible early clinical manifestation of cerebral infarction, so that timely management of vascular risk factors can be instituted to potentially prevent future stroke events and to avoid further deterioration of cognitive health,” conclude the authors.
Stroke is the second most common cause of cognitive impairment and dementia. The accumulation of lacunar infarcts, ischemic white matter disease and cerebral hypoperfusion are the most common causes of cognitive impairment/dementia due to stroke that can go unrecognized for up to 30 years, by which time there is substantial impairment.
These types of stroke predominantly affect the connections between areas of cortex that associate complex types of information, the disruption of which leads to impaired cognition and function. Larger strokes are usually detected clinically and cognitive impairment is thus more likely to be detected early on. Detecting stroke early allows initiation of the appropriate treatment that can prevent or substantially delay the onset and progression of cognitive impairment/dementia.
How Much Stroke Can Cause Cognitive Impairment?
The smallest amount of stroke necessary to cause cognitive impairment/dementia is greater than 10 ml and less than 50 ml, which amount to between 1% and 4% of the brain’s volume. Cognitive impairment/dementia can result from stroke volumes smaller than 10 ml when they affect the hypothalamus, thalamus, brainstem or hippocampus.
The most common types of cognitive deficits arising from stroke are disturbances of attention, language syntax, delayed recall and executive dysfunction affecting the ability to analyze, interpret, plan, organize, and execute complex information. The risk of vascular cognitive impairment and dementia as well as the rate of cognitive decline in cerebrovascular disease is highly dependent upon the control of the underlying risk factors for stroke. If left untreated, vascular cognitive impairment and dementia do decline.
The risk of developing cognitive impairment secondary to stroke begins at age 50. Risk is highest in those persons with vascular risk factors, including hypertension, hyperlipidemia, atherosclerotic vessel disease affecting the aorta, carotid, vertebrobasilar, or major cerebral arteries, homocysteinemia, diabetes, heart disease, hypotension, obesity, physical exercise less than two days per week and 30 minutes per session, smoking, alcohol dependence,
coagulopathies, and prior stroke.
Canadian Medical Association Journal