Age Profiles of Cognitive Decline and Dementia in Late Life in the Aging, Demographics, and Memory Study

Abstract

Objectives To better understand the temporal dynamics of progression from cognitive decline to onset of dementia in the dementia-free older population in the U.S. Methods We used longitudinal data from a diverse national population-based sample of older adults (N=531) in the Aging, Demographics and Memory Study (ADAMS) from the Health and Retirement Study (HRS) with repeated measures of cognitive function and dementia diagnosis during 12 years of follow-up from 1996 to 2009. We employed joint latent class mixed models to estimate the association between cognitive change and competing risks of dementia and non-dementia death and identify heterogeneity in the age profiles of such association adjusting for baseline characteristics. Results Our analyses found three latent classes with distinct age profiles of cognitive decline and associated risk of dementia and mortality: “Rapid Cognitive Decline” (19.6%), “Moderate Progression” (44.6%), and “Optimal Cognitive Aging” (35.8%). When simultaneously accounting for cognitive trajectories and time-to-dementia/death, we also found associations of baseline covariates with slope of cognitive decline (e.g., steeper decline among non-Hispanic Blacks and more educated) and risk of dementia (e.g., greater risk for females and apolipoprotein E [APOE-4] carriers, but no difference by education level) that differ substantially from those in separate longitudinal mixed models or survival models. Discussion The differential age patterns of cognitive decline predicting dementia incidences identified in this study suggest variation in the course of cognitive aging in older adults that may inform future etiological and intervention studies.

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

“…Better memory and overall cognitive performance for women than men on average has been found previously (Levine et al, 2021; Walsh et al, 2022). The direction and size of gender difference, however, vary from early to late life.…”

“…Prior research suggests the potential early onset of aging-related cognitive decline indicated by a slowing in memory and executive function in the 30s (Albert et al, 2007; Salthouse, 2009; Wilson et al, 2002) and mild declines in cognitive performance over time in older adults (Salthouse, 2019; Schaie, 2013; Walsh et al, 2022). The age patterns of performance of cognitive tasks following a “peak-plateau-decline” trajectory are largely implicitly understood (Rosano, 2020) rather than explicitly tested.…”

“…Examining the longitudinal nature (timing and course) of cognitive changes preceding late life dementia is a critical first step in understanding the developmental trajectory of cognitive aging and environmental risk factors (Albert et al, 2007; Whalley et al, 2006; Wilson et al, 2002). Previous research shows differences in the shape of trajectories of cognitive change that are predictive of disease risk: not only deficits at baseline, but also a steeper slope of decline in memory and overall cognitive performance at follow-ups increased subsequent risk of dementia (Albert et al, 2007; Walsh et al, 2022). These findings are from older adults and suggest distinctions between normal cognitive aging (stable declines) and pathological cognitive declines (progressive declines) (Alty et al, 2023; Salthouse, 2019) that should be further investigated in longitudinal studies of adults of all ages in that cognitive aging is widely thought to be a lifelong process.…”

Cognitive interventions for memory and psychological well-being in aging and dementias

“…For example, the time between a dementia diagnosis and loss of independence can be relatively quick, while others live with the diagnosis for decades ( Jagust, 2018 ). Exhibiting interindividual change, a person may exhibit preservation of function for many years, followed by a precipitous decline ( Walsh et al, 2022 ). Understanding the rate of change and trajectory of decline is critical for maintaining activities of daily living, and thus independence ( Hertzog et al, 2008 ; Walsh et al, 2022 ).…”

“…Exhibiting interindividual change, a person may exhibit preservation of function for many years, followed by a precipitous decline ( Walsh et al, 2022 ). Understanding the rate of change and trajectory of decline is critical for maintaining activities of daily living, and thus independence ( Hertzog et al, 2008 ; Walsh et al, 2022 ). Given a diagnosis of dementia, the ability to retain function presents an important leverage point in the disease.…”