Researchers from the US, Taiwan and South Korea find that the risk of future stroke is 39% higher among patients with cognitive impairment than those with normal cognitive function, according to a new study published in the Canadian Medical Association Journal (CMAJ).

Cognitive impairment ranges from mild to severe. Individuals experiencing mild impairment may begin to notice changes in cognitive functions but can continue to go about their daily tasks. Severe impairment can result in losing the ability to understand the meaning or significance of something and the faculty to speak or write, leading to an inability to live independently.

Cognitive impairment is not caused by any one particular disease or condition, or limited to a specific age group. Alzheimer's disease and other dementias - in addition to conditions such as stroke, traumatic brain injury, and developmental disabilities - can cause cognitive impairment.

Indicators that a person has cognitive impairment include:

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More than 16 million people in the US are living with cognitive impairment, and it is a major contributor to disability and dependence worldwide.
  • Memory loss
  • Trouble learning new things
  • Loss of concentration
  • Frequently asking the same question or repeating the same story
  • Not recognizing people and places
  • Having issues exercising judgment, such as knowing what to do in an emergency
  • Changes in mood or behavior
  • Vision problems
  • Struggling with making decisions that affect their everyday life
  • Difficulty planning and carrying out tasks, such as following a recipe or keeping track of monthly bills.

More than 16 million people in the US are living with cognitive impairment, and it is a major contributor to disability and dependence worldwide. Globally, stroke is the leading cause of long-term disability among adults and the 2nd leading cause of death. Stroke is the 4th leading cause of death in the US with over 125,000 deaths annually.

Several previous study results inconsistent

Several studies have assessed the link between cognitive impairment and risk of subsequent stroke, but results have been inconsistent. The researchers of this latest study aimed to determine the association between cognitive impairment and risk of future stroke.

"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," notes Dr. Bruce Ovbiagele, chair of the Department of Neurology at the Medical University of South Carolina.

The study investigators identified 18 cohort studies and conducted a meta-analysis, involving 121,879 participants, of which 7,799 later reported strokes. The majority of the studies were from North American or European countries. One was conducted in Taiwan and three were an international collaboration. All but one of the studies included both men and women.

As a guideline on the definition of cognitive impairment, the mini-mental state examination (MMSE) score process was used. The MMSE test, also called neurocognitive testing, is scored from 0 to 30. The test is also divided into sections, each with its own score. These results help show which part of someone's thinking and memory may be affected - a score of 25-30 is considered normal.

The results were analyzed only from studies that used a widely adopted definition of cognitive impairment (i.e., mini-mental state examination score <25 or nearest equivalent) and explored the association of this definition of cognitive impairment with future stroke.

Increased risk of fatal stroke and ischemic stroke with cognitive impairment

A higher rate of stroke was observed in people with cognitive impairment than in people with normal cognitive function.

On further analyses performed on stroke outcome (fatal v. nonfatal) and type of stroke (ischemic v. hemorrhagic), the academics found that baseline cognitive impairment was associated with an increased risk of fatal stroke but not with nonfatal stroke. When they combined data by ischemic or hemorrhagic stroke, an association was found between baseline cognitive impairment and an increased risk of ischemic stroke but no increased risk of hemorrhagic stroke.

The authors of the study write:

"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. This risk increased to 64% when a broadly adopted definition of cognitive impairment was used."

Previous studies have shown that atherosclerosis and inflammation are associated with an increased risk of both cognitive impairment and stroke. Increased coronary artery calcification is interconnected with poor memory in midlife and independently increases the risk of future stroke in the general population.

Cognitive impairment is also connected with high variability in blood pressure, which itself is a risk factor for stroke. Finally, cognitive impairment can be linked to factors such as lack of medication compliance, poor diet, physical inactivity, frailty and depression, which increase the risk of stroke.

Findings suggest that identifying people with cognitive impairment may provide opportunities to reduce the future burden of stroke through the timely implementation of evidence-based prevention strategies.

"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.

Earlier this year, Medical News Today reported how mild cognitive impairment is linked to early death. People who have thinking problems - but who have an intact memory - may be more prone to early death than people who have no problems with their memory or thinking. These are the findings of one of the first studies to look at the relationship between early death and mild cognitive impairment.