Abstract
ObjectiveTo evaluate cohort differences in cognitive performance in older men and women born and assessed 28 years apart.MethodsData in this study were drawn from two age-homogeneous cohorts measured in the same laboratory using the same standardized cognitive performance tests. Participants in the first cohort were born in 1910 and 1914 and assessed in 1989–1990 (Evergreen project, n = 500). Participants in the second cohort were born in 1938 or 1939 and 1942 or 1943 and assessed in 2017–2018 (Evergreen II, n = 726). Participants in both cohorts were assessed at age 75 and 80 years and were recruited from the population register. Cognitive performance was measured using the Digit Span test from the Wechsler Memory Scale (WMS), Digit Symbol test from the Wechsler Adult Intelligence Scale (WAIS) and phonemic Verbal Fluency test from the Schaie-Thurstone Adult Mental Abilities Test. Reaction time assessing motor and mental responses was measured with a simple finger movement task, followed by a complex finger movement task. T-tests were used to study cohort differences and linear regression models to study possible factors underlying differences.ResultsWe found statistically significant cohort differences in all the cognitive performance tests, except for the digit span test and simple movement task in men, the later-born cohort performing better in all the measured outcomes.ConclusionsThe results of this study provide strong evidence that cognitive performance is better in more recent cohorts of older people compared to their counterparts measured 28 years earlier.
Highlights
Aging is associated with a general decline in cognitive performance, such as memory, attention, processing speed and problem solving, and affects the way people learn and perform [1]
Based on evidence from standardization samples of the Wechsler Intelligence Scale for Children (WISC) tests, young Americans gained about 22 IQ points over the 70 years between 1932 and 2002 [4]
The results depend on several factors, such as the cognitive domains assessed, participants’ age range, the number of years between birth cohorts and whether studies have examined cohort differences in cognitive performance trajectories [14]
Summary
Aging is associated with a general decline in cognitive performance, such as memory, attention, processing speed and problem solving, and affects the way people learn and perform [1]. The “Flynn effect” [2], i.e., later-born cohorts outperforming earlier born cohorts in cognitive abilities, has been observed for older people when measured at the same chronological ages [3]. The results depend on several factors, such as the cognitive domains assessed, participants’ age range, the number of years between birth cohorts and whether studies have examined cohort differences in cognitive performance trajectories [14]. In a more recent study, Brailean et al [14] found that at the age 65 to 75 the laterborn cohort (1931–1941) had better general cognitive performance, inductive reasoning and processing speed compared to the earlier-born cohort (1920–1930). The cohort differences in general cognitive performance and inductive reasoning were explained by better education in the later cohort, but processing speed was not. Christensen et al [15] studied cohort differences in elderly Danish individuals and found that at age 95, a 1915 birth cohort
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