An Early and Unequal Decline: Life Course Trajectories of Cognitive Aging in the United States

Abstract

Objectives Cognitive aging is a lifelong process with implications for Alzheimer’s disease and dementia. This study aims to fill major gaps in research on the natural history of and social disparities in aging-related cognitive decline over the life span. Methods We conducted integrative data analysis of four large U.S. population-based longitudinal studies of individuals aged 12 to 105 followed over two decades and modeled age trajectories of cognitive function in multiple domains. Results We found evidence for the onset of cognitive decline in the 4th decade of life, varying gender differences with age, and persistent disadvantage among non-Hispanic Blacks, Hispanics, and those without college education. We further found improvement in cognitive function across 20th century birth cohorts but widening social inequalities in more recent cohorts. Discussion These findings advance an understanding of early life origins of dementia risk and invite future research on strategies for promoting cognitive health for all Americans.

Longitudinal trajectories of cognitive aging

“…as the course of cognitive function over time or age, have used two or more waves of data, and methodologies that take into account the heterogeneity of the populations. These studies show that age-related cognitive changes are relatively slow but start in midlife [5], around the fourth decade of life [6], and that differences in cognitive scores reach significance every two decades throughout different age groups [5]. Still, some longitudinal studies show an acceleration of cognitive decline in the seventh decade of life [6].…”

“…Declarative memory declines much more than implicit memory [14 && ]. Episodic memory may be significantly impaired as people age [6], in contrast with semantic memory, which may hardly be affected by age-related cognitive decline [14 && ]. Memory decline has been considered to be associated with damage of subcortical white matter, and closely associated with hippocampus atrophy.…”

“…Therefore, the individuals' lifelong development and experiences must be considered [13]. Yang et al [6] have found a more favorable aging-related cognitive change across 20th century birth cohorts (higher average cognitive abilities and slower rates of decline) related to previous generations, which probably reflects sociocultural influences due to advances in educational attainment and associated protective factors.…”

Impact of Optimism on Cognitive Performance of People Living in Rural Area: Findings From a 20-Year Study in US Adults

“…Episodic memory is associated with one’s recollection of time and place-specific personal experiences, while executive functions denote cognitive abilities such as planning, reasoning, organizing, and problem-solving ( P. L. Lee, 2014 ). Although both of these cognitive abilities are associated to some extent with age-related decline ( Glisky et al, 2022 ; McDaniel et al, 2022 ; Yang et al, 2024 ), the rate of individual decline has been found to be associated with facets of positive psychological well-being, thereby showing interpersonal and intrapersonal variation ( Cheng et al, 2023 ).…”