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 (A beta) 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 Question-naire) moderates the relationship between self-reported sleep (measured via the Pittsburgh Sleep Quality Index), cognition, and brain A beta. 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 A beta burden (measured by positron emission tomography) as the outcome. Result: Physical activity moderated the relationship between sleep duration and episodic memory (beta =-0.10, SE =0.03, p = .005), and sleep efficiency and episodic memory (beta =-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 A beta (beta =-0.13, SE =0.06, p = .031), and overall sleep quality and brain A beta (beta = 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 A beta.