Lifestyle activities, mental health and cognitive function in adults aged 50 to 90 years

Abstract

In a series of studies, lifestyle activities, mental health and aerobic fitness were investigated in relation to mean RT and response time variability (trial-to-trial variability in RT performance) obtained from a battery of cognitive measures in 257 healthy adults aged 50 to 90 years (M = 63.60). Cognition was assessed across four domains; psychomotor performance, executive function, visual search and word recognition. Hierarchical multiple regression analyses and structural equation modelling (SEM) were used to explore associations between age and outcome measures in a mediated-moderator analysis. The dedifferentiation of cognition and the dissociation between the outcome measures of mean RT and response time variability was also explored. Additionally, the neural correlates of response time variability were investigated using functional magnetic resonance imaging (fMRI). The findings indicated that poor mental health was associated with greater within-person (WP) variability and slower mean RTs and that this effect was greater in older adults. Higher lifestyle activity scores and higher aerobic fitness (VO2max) attenuated negative age gradients in WP variability and mean RT. Analyses suggested that the above effects were mediated by executive function. There was no evidence of dedifferentiation across cognitive domains and there was selective dissociation between the measures of mean RT and WP variability. The fMRI results suggested that WP variability was associated with fluctuations in executive control and, relatedly, attentional lapses. Overall, the findings suggest that executive function mediates a substantial portion of age-related variance in cognition and that this association is influenced by moderators such as an active lifestyle, aerobic fitness and mental health. The findings underline the potential benefits and importance of interventions to help maintain and promote mental health, and active lifestyles, in old age.