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• Physical activity negates some of the adverse impacts poor sleep has on cognition. • Physical activity may improve cognition through improving sleep. • Sleep and physical activity influence cognition via shared and separate pathways. • Intervention studies required for casual interpretation of results. Physical activity and exercise can improve cognitive function and reduce the risk for dementia. Other lifestyle factors, including sleep, are associated with cognitive function and dementia risk, and exercise is an effective therapeutic strategy for improving sleep. Based on these associations, it has been hypothesised that sleep might be an important mediator for the effects of exercise on cognition. Here, we review the current literature to evaluate whether sleep and physical activity are independently or jointly associated with cognitive function. The extant literature in this area is minimal, and the causal relationships between physical activity, sleep and cognition have not been examined. A small number of cross-sectional studies in this area suggest that physical activity may attenuate some of the negative impact that poor sleep has on cognition, and also that sleep may be a mechanism through which physical activity improves cognitive abilities. Further research may enable the development of individually tailored intervention programs to result in the greatest cognitive benefit, ultimately delaying the onset of Alzheimer's disease. [ABSTRACT FROM AUTHOR]

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. 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. 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. 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). Our findings suggest that physical activity may play an important role in the relationship between sleep and cognitive function, and brain Aβ. • Physical activity moderates associations between sleep and episodic memory. • Physical activity moderates associations between sleep and brain beta-amyloid. • Physical activity may mitigate the negative impact of poor sleep on cognition. [ABSTRACT FROM AUTHOR]