Lower Cognitive Scores and Stroke Risk: Does Age Matter?

Lower scores on tests of thinking, memory, and processing speed in adults in their sixties are associated with a higher risk for a first stroke years later, a longitudinal study showed.In a population-based cohort of nearly 5000 adults, those aged 60-69 years who had the lowest scores for global cognition, episodic memory, and perceptual speed had a 66%-86% higher risk for stroke than those with the highest cognitive scores.These associations were not significant among adults aged 70 years or older, suggesting that the link between cognitive performance and future risk for stroke may vary across older age groups.“Cognitive testing might be an important screening tool for future cerebrovascular events for this age group,” lead investigator Alice Askemyr, MD, a geriatrics researcher at Lund University and Skåne University Hospital, both in Malmö, Sweden, and colleagues wrote.“Our results were independent of behavioral, psychological, and physiological factors and adds new insights on age- and sex-specific associations of stroke among those with lower cognitive functioning,” they added.The study was published online on September 30 in the Journal of the American Heart Association.Cognition and Stroke RiskStroke and cognitive impairment share several risk factors, including hypertension, diabetes, physical inactivity, smoking, and excessive alcohol consumption. Previous research has also linked cognitive impairment with an increased risk for stroke, although findings have varied by cognitive domain and age.“We chose to investigate different age spans because the older population is very diverse. For instance, while many people in their sixties may have only a few medical conditions, people in their eighties often suffer from multiple medical conditions and take numerous medications,” Askemyr said in a statement. “Furthermore, what serves as a risk factor in early life might not serve as one if it is acquired later in life and vice versa.”Investigators used data from the Good Aging in Skåne study, a population-based prospective cohort of adults randomly selected from five municipalities in southern Sweden. The mean follow-up with 12.3 years, with assessments in 2001, 2007, or 2012 and followed through the end of 2023 or until the first stroke or death.The study included 4912 adults (46.2% men) without dementia, prior stroke, or transient ischemic attack at baseline. The majority of participants (n = 3094) were aged 60-69 years, 494 were aged 70-79 years, and 1184 were aged 80 years or older. During the follow-up, 572 participants had a first stroke.Participants completed tests that assessed episodic memory, perceptual speed, verbal fluency, and selected executive functions. The investigators also calculated a global cognition score and divided scores into age-specific tertiles, with the highest tertile as the reference group.The Risk for Stroke in the SixtiesAcross the full cohort, lower perceptual speed was associated with a higher risk for stroke (hazard ratio [HR], 1.40). After full adjustment, however, associations between stroke and global cognition, episodic memory, executive function, and verbal fluency were not statistically significant.The age-specific analyses revealed something different. Among participants aged 60-69 years, those in the lowest tertile for global cognition had an 86% higher risk for stroke than those in the highest tertile (HR, 1.86; 95% CI, 1.27-2.69).The risk for stroke was 68% higher among those with lower scores in episodic memory (HR, 1.68; 95% CI, 1.21-2.33) and 66% higher among those with lower perceptual speed scores (HR, 1.66; 95% CI, 1.19-2.32).The risk for stroke also increased as scores for global cognition, episodic memory, and perceptual speed decreased (P = .007, .007, and .006, respectively). Executive function and verbal fluency were not significantly associated with the risk for stroke in this age group.The findings were less pronounced among adults in their seventies, with none of the cognitive measures showing a significant increase in the risk for stroke. Although lower perceptual speed was linked to increased risk for stroke among adults aged 80 years or older in unadjusted models, the findings were no longer significant after adjustment.There were also differences by sex in the 60-69 age group. Among men, those with low global cognition had more than twice the risk for stroke (HR, 2.11), as did those with low episodic memory (HR, 2.30). Low perceptual speed was also linked to higher risk for stroke in men (HR, 1.77), whereas none of these findings were statistically significant in women.The findings need further study, particularly because there were few hemorrhagic strokes and relatively few stroke cases in some groups, the investigators noted.The study was observational, so it could not determine whether lower cognitive performance directly contributed to stroke. There was also a lack of baseline MRI data to assess underlying cerebrovascular changes.Why Age May MatterLower cognitive performance may reflect underlying brain changes that precede a clinically apparent stroke, Askemyr suggested.“So-called ‘silent’ brain injuries can affect both cognitive functioning and the future risk of stroke,” she said in the statement.“They affect roughly 70% of adults over age 70, so their effects may be easier to detect among people in their sixties, when such injuries and other factors that can affect cognition, including medical conditions and medications, are less common,” she added.Lower cognitive performance may be worth considering when assessing the risk for stroke in otherwise healthy adults in their sixties, the investigators wrote.Future MRI studies are needed to determine whether underlying cerebrovascular changes help explain the link between lower cognitive performance and stroke, including differences by age, sex, and stroke subtype, they concluded.The Good Aging in Skåne study was funded by the Swedish Ministry of Health and Social Affairs, the County of Region Skåne, and the Swedish Research Council. Disclosure information for study authors is available in the original study publication.