The interaction between physical activity and sleep on cognitive function and brain beta-amyloid in older adults

Background: Lifestyle factors such as physical activity and optimal sleep are associated with better cognition and lower levels of Alzheimer's disease (AD) biomarkers, including brain beta-amyloid (Aβ) burden. Objective: We utilised cross-sectional data from the Australian Imaging, Biomarkers and Lifestyle (AIBL) study to determine whether self-reported physical activity (measured via the International Physical Activity Questionnaire) moderates the relationship between self-reported sleep (measured via the Pittsburgh Sleep Quality Index), cognition, and brain Aβ. Methods: Participants were 349 community-dwelling cognitively normal older adults (75.3 ± 5.7 years), all of whom underwent comprehensive cognitive assessment. Data from a subset of participants (n = 201) were used for analyses with brain Aβ burden (measured by positron emission tomography) as the outcome. Result: Physical activity moderated the relationship between sleep duration and episodic memory (β =-0.10, SE =0.03, p = .005), and sleep efficiency and episodic memory (β =-0.09, SE =0.04, p = .011), such that greater amounts of physical activity mitigated the impact of suboptimal sleep duration and efficiency on episodic memory. Physical activity also moderated the relationship between sleep duration and brain Aβ (β =-0.13, SE =0.06, p = .031), and overall sleep quality and brain Aβ (β = 0.13, SE =0.06, p = .027). Conclusion: Our findings suggest that physical activity may play an important role in the relationship between sleep and cognitive function, and brain Aβ.