The older population is more cognitively able than in the past and age-related deficits in cognition are diminishing over time

Abstract

Increased lifespan in the population was historically driven by reductions in infant mortality but is now driven by reduced mortality in older adults. Research is beginning to show reduced incidence of many age-related diseases, but there have been some mixed trends observed in assessment of cognitive ability in healthy ageing research. Across three studies, time-based trends in older adults’ cognition were assessed. In a meta-analysis of literature largely studying different waves of longitudinal data, Study 1 showed cognitive improvement in later-recruited waves of older adults compared to earlier-recruited waves. In a second meta-analysis of studies comparing young and older adults’ cognition, Study 2 showed that age-related cognitive deficits were becoming smaller over time. Finally, in an analysis of historic data from a single laboratory, Study 3 confirmed the findings of Study 2 and demonstrated that time-based reductions in age-related cognitive deficits were largely driven by improvement in cognition over time in older groups, whilst young adults’ cognition remained relatively flat across time. It is argued that later tested groups of older adults are benefiting from environmental advantages to cognition (e.g., education, healthcare, nutrition) that might previously have mainly applied to young adult groups in research. These results have implications for cognitive ageing research which will likely yield smaller age differences than historic work. It is also argued that definitions of cognitive impairment related to dementia diagnosis may need to be periodically revised.