Abstract
ABSTRACT In the present study, we decomposed between- and within-person effects and examined moderators of the longitudinal physical activity-cognition association. Participants (N = 1722) were drawn from the Betula study and we included four waves of data across 15 years. Bayesian multilevel modeling showed that self-reported physical activity did not predict changes in cognitive function. Physical activity positively predicted cognitive performance at baseline, and the relations were stronger for more active (compared to less active) older adults. Physical activity had a positive within-person effect on cognitive function. The within-person effect of physical activity on episodic memory recall was stronger for participants who on average engaged in less physical activity. The within-person effect on verbal fluency was stronger for participants with more education. Our results suggest that preserving cognitive functioning in old age might be more a matter of what you do in old age than reflecting what you did earlier in life.
Highlights
Numerous studies have identified physical activity as a potent lifestyle factor that plays a critical role in preserving and even enhancing cognitive function across the life course (Engeroff et al, 2018; Prakash et al, 2015)
In the first set of models we examined the effects of baseline level of physical activity on baseline levels and changes in cognitive function over time as well as interaction effects between baseline level of physical activity and age, apolipoprotein ε4 (APOE ε4) status, years of education, and sex
When adding the interaction terms to the model, the interaction between baseline level of physical activity and age was a credible predictor of baseline level of verbal fluency. These results show that older participants who engaged in more physical activity at baseline showed better verbal fluency at baseline compared to older participants who were less active
Summary
Numerous studies have identified physical activity as a potent lifestyle factor that plays a critical role in preserving and even enhancing cognitive function across the life course (Engeroff et al, 2018; Prakash et al, 2015). Erickson et al, 2011; Jonasson et al, 2017) and meta-analyses of intervention studies have shown beneficial effects on many different cognitive domains (Barha et al, 2017; Colcombe & Kramer, 2003; Etnier et al, 2019; Northey et al, 2018; Smith et al, 2010). Despite the wealth of evidence supporting the cognitive benefits of physical activity, few studies have decomposed between- and within-person effects (Kowalski et al, 2018; Robitaille et al, 2014). Within-person effects capture how variation relative to a person’s own mean is related across variables and these variables are described as timevarying (Hoffman, 2015). Decomposing between- and within-person effects is important because results often differ between levels (Bielak et al, 2014; Kowalski et al, 2018; Schmiedek et al, 2019)
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