Stability of Estimated Premorbid Cognitive Ability over Time after Minor Stroke and Its Relationship with Post-Stroke Cognitive Ability

Abstract

Considering premorbid or “peak” adult intelligence (IQ) is important when examining post-stroke cognition. The stability of estimated premorbid IQ and its relationship to current cognitive ability in stroke is unknown. We investigated changes in estimated premorbid IQ and current cognitive ability up to three years post-stroke. Minor stroke patients (NIHSS < 8) were assessed at one to three months, one and three years’ post-stroke. The National Adult Reading Test (NART) and Addenbrooke’s Cognitive Examination-Revised (ACE-R) were used to estimate premorbid IQ (NART IQ) and current cognitive ability respectively at each time-point. Baseline demographics, vascular and stroke characteristics were included. Of the 264 patients recruited (mean age 66), 158 (60%), 151 (57%), and 153 (58%) completed cognitive testing at each time-point respectively. NART IQ initially increased (mean difference (MD) = 1.32, 95% CI = 0.54 to 2.13, p < 0.001) before decreasing (MD = −4.269, 95% CI = −5.12 to −3.41, p < 0.001). ACE-R scores initially remained stable (MD = 0.29, 95% CI = −0.49 to 1.07, p > 0.05) before decreasing (MD = −1.05, 95% CI = −2.08 to −0.01, p < 0.05). Adjusting for baseline variables did not change the relationship between NART IQ and ACE-R with time. Increases in NART IQ were associated with more education. For ACE-R, older age was associated with declines, and higher NART IQ and more education was associated with increases. Across 3 years, we observed fluctuations in estimated premorbid IQ and minor changes in current cognitive ability. Future research should aim to identify variables associated with these changes. However, studies of post-stroke cognition should account for premorbid IQ.

Verbal intelligence is a more robust cross-sectional measure of cognitive reserve than level of education in healthy older adults

“…Secondly, measures of verbal intelligence may reflect wider lifetime educational and cognitive experiences as compared to years of education which is generally restricted to early-life formal education [79][80][81][82] and typically neglects to consider later-life education which has been positively associated with cognitive function [116,117]. In this sense, verbal intelligence could be considered a dynamic CR proxy which can change over time [118,119], as it may increase from young to mid-adulthood before decreasing in older adulthood [120]. In contrast, years of education may be considered a static CR proxy [31].…”

Impact of Small Vessel Disease Progression on Long-term Cognitive and Functional Changes After Stroke

“…Moreover, the interval between stroke presentation and baseline MRI assessment is an important factor (eTable 2, links.lww.com/WNL/B796 ) because SVD lesions are dynamic. 1 In the assessment of poststroke cognition, it is important to adjust for factors that are associated with premorbid cognitive ability, 22 later-life cerebrovascular disease, 41 , 42 and cognitive decline. 42 One previous study adjusted for ICV and education, 12 and another adjusted for premorbid IQ.…”

“…Study procedures, including baseline variables and stroke subtyping, have been described in full previously. 2 , 9 , 20 - 22 Participants underwent the Addenbrooke's Cognitive Examination–Revised version (ACE-R) at all 3 visits. The ACE-R is sensitive to multidomain cognitive impairment after stroke, similar to the Montreal Cognitive Assessment.…”

“…At baseline, participants completed the National Adult Reading Test (NART), a durable measure of premorbid intelligence. 22 …”

Verbal Intelligence, Not Level of Education, Robustly Assesses Cognitive Reserve

“…Secondly, measures of verbal intelligence may re ect wider lifetime educational and cognitive experiences as compared to years of education which is generally restricted to early-life formal education (54,104,113,114) and typically neglects to consider later-life education which has been positively associated with cognitive function (115,116). In this sense, verbal intelligence could be considered a dynamic CR proxy which can change over time (117)(118)(119) whereas years of education may be considered a static CR proxy (30). Despite the widespread use of educational attainment as an individual CR proxy, our results suggest that it should only be used as an individual proxy where verbal intelligence is not available.…”