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."

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.