Delayed onset of cognitive terminal decline in later born cohorts: Evidence from a longitudinal study of two cohorts born 29-years apart.

Abstract

In this study, we evaluated birth cohort (i.e., generational) differences in the onset and rate of acceleration in cognitive decline prior to death (i.e., terminal decline [TD]). We obtained data from two cohorts, born in 1901-1902 (n = 755, 64% females) and 1930 (n = 347, 48% females), identified and sampled at age 70 from the same city population and assessed on the same cognitive tests at ages 70, 75, 79, 85, and 88. The 1901-1902 cohort was additionally assessed at ages 90, 92, 95, 97, 99, and 100. The outcome was defined at each measurement occasion by a composite score of three cognitive tests assessing spatial ability, perceptual and motor speed, and reasoning. Date of death was obtained from population register, with the last update in April 2023, covering over 99% and 38% of the cohort members, respectively. We fitted a random TD change point model to the data while accounting for sex and education. Findings revealed expected TD onset (as conditioned on male with formal education) 5.17 (95% highest density interval [2.54, 8.05]) years prior to death in the 1901-1902 cohort, with an acceleration in rate of decline by a factor of 4.43 within the TD phase. This estimate was delayed by 2.53 (95% highest density interval [5.68, 0.10]) years in the 1930 cohort, with an acceleration by a factor of 5.16 within the TD phase. To the best of our knowledge, this is the first study to present evidence indicating that today's birth cohort experience, on average, a shorter TD phase in comparison to earlier born cohorts. (PsycInfo Database Record (c) 2024 APA, all rights reserved).