In a recent study published in the Journal of Epidemiology & Community Health, researchers investigated the relationship between teenage cognitive performance and stroke in adulthood.
Study: Cognitive function in adolescence and the risk of early-onset stroke. Image Credit: Komsan Loonprom/Shutterstock.com
Background
Stroke is a public health problem since it causes high hospitalization rates, long-term disability, and death. While the incidence of stroke in elderly individuals is decreasing, it is increasing among those under the age of 50.
Stroke survivors may suffer long-term physical and psychological consequences, emphasizing the need to identify risk factors for stroke of early onset.
Poor cognitive ability may be associated with social health determinants such as socioeconomic position and education, both of which are highly associated with stroke risk.
Previous research has shown conflicting results on the relationship between cognitive function and stroke risk, with earlier studies focusing primarily on cognitive performance in middle age.
About the study
In the current national study, researchers studied the relationship between adolescent cognitive function and stroke among 1.70 million adolescents.
The researchers included 1,741,345 teenagers who underwent extensive cognitive function assessments between the ages of 16 and 20 years old before requiring military duty between 1987 and 2012.
They eliminated those who lacked cognitive function data or died before January 1, 2014, at the time of the Israeli National Stroke Registry's (INSR) creation.
The military pre-recruitment multiple-choice evaluation consisted of a general intelligence test administered by professionals. This exam included four subtests, i.e., Otis-R, Similarities-R, Arithmetic-R, and Raven's Progressive Matrices-R.
Otis-R assesses verbal comprehension and execution; Similarities-R evaluates verbal categorization and abstraction; Arithmetic-R assesses mathematical ability, concept manipulation, and concentration; and Raven's Progressive Matrices-R assesses visual-spatial problem-solving and non-verbal-type abstract reasoning.
The cumulative score of the four evaluations yields a nine-point scale assessment of cognition performance. The researchers divided the cognitive score into z-scores based on gender and year of examination.
They divided cognitive performance into the following categories: high [8.0 to 9.0, intelligence quotient (IQ) score >118], medium (4.0 to 7.0, IQ scores ranging from 89 to 118), and low (1.0 to 3.0, IQ score <89).
The researchers linked participant data with the National Stroke Registry (NSR). The study endpoint was an incident first stroke, an ischemic stroke, and an intracerebral hemorrhage, as recorded by the INSR.
The researchers used Cox proportional hazards regression models to determine the hazard ratios (HR) for the initial ischemic stroke between 2014 and 2018.
Study covariates included age, biological sex, body mass index (BMI), educational attainment, residential socioeconomic status, and diabetes. The researchers performed follow-up evaluations until the stroke episode, December 31, 2018, or death, whichever came first.
Results
The mean age of 1,741,345 participants was 17 years; 42% were female, and 18%, 70%, and 12% had low, medium, or excellent cognitive ability, respectively. The group with impaired cognitive function was more likely to be overweight or obese, have not completed high school, and live in a low-income neighborhood.
Over 8,689,329 follow-up years, the researchers recorded 908 incident stroke cases (141 hemorrhagic and 767 ischemic). The average age of stroke incidence was 40 years (the maximum age was restricted to 50 years). Forty-five individuals with new-onset stroke died (5% of all stroke cases), with 62% of them occurring within one month of the incident.
BMI- and sociodemographic status-controlled HR values for stroke in low- and medium-level cognitive ability groups were 2.7 and 1.8, respectively, compared to individuals with high cognitive ability.
Poorer cognitive ability groups had higher rates of both types of strokes, notably ischemic stroke, which increased from 3.9 to 14 instances per 106 individual years.
The researchers found dose-response correlations, with each unit of worse cognition z-score related to a 33% higher stroke risk (HR, 1.3). These relationships were comparable for ischemic stroke, lower for hemorrhagic stroke, remained in sensitivity assessments controlling for diabetes and hypertension, and were prominent before the age of 40.
Among male and female adolescents with poor cognitive ability, the HR values were 2.9 and 3.2, respectively. After correcting for numerous variables, adolescents with low and medium cognitive functioning had a three-fold and two-fold elevated risk of ischemic stroke.
The study findings showed that poor teenage mental capacity is associated with a three-fold increased risk of ischemic stroke by 50 years of age.
The positive association between low cognitive function throughout adolescence and stroke risk is independent of sociodemographic background, BMI, or health condition. The study findings indicate that comprehensive evaluations beyond standard risk factors for stroke are required.
Cognitive performance may assist in identifying high-risk individuals, allowing for early intervention strategies to address possible mediating variables such as education, health illiteracy, and health-related behaviors. Early social and health assistance for those with poorer cognitive function is critical.
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