What is the association between sedentary behaviour and cognitive function? A systematic review

Correspondence to Teresa Liu-Ambrose, Faculty of Medicine, Aging, Mobility and Cognitive Neuroscience Laboratory, Department of Physical Therapy, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, CA, 212-2177 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 1Z3; [email protected]

Introduction

Currently, one new case of all-cause dementia is detected every 4 seconds around the world.¹ All-cause dementia prevalence is also expected to rise since the number one risk factor is age² and the number of older adults worldwide is increasing.³ Thus, the current lack of effective pharmaceutical treatments for all-cause dementia is creating an urgency to develop non-pharmacological strategies to prevent, or at least delay, the onset and progression of the disease.⁴ As a result, lifestyle approaches have become an important line of scientific inquiry and public interest.

Increasing physical activity is one promising strategy to promote or maintain cognitive health in later life.⁵ Strong and accumulating empirical evidence suggests regular physical activity of an intensity ≥3.0 metabolic equivalents (METs) reduces the risk of all-cause dementia by 28%.⁶ Thus, meeting current physical activity guidelines for older adults of 150 min/week of moderate-to-vigorous physical activity (ie, activity of ≥3.0 METs) may help reduce all-cause dementia risk, prevent other comorbidities including type 2 diabetes and cardiovascular disease, and reduce all-cause mortality.^7–9 Since most older adults are physically inactive (ie, do not engage in ≥150 min/week of moderate-to-vigorous physical activity) and fall short of these recommendations,¹⁰ increasing moderate-to-vigorous physical activity among older adults has become a public health priority. As such, it is estimated 17.7% of Alzheimer's disease cases could be prevented by recommended amounts of moderate-to-vigorous physical activity.¹¹

Accumulating evidence also suggests high amounts of sedentary behaviour can increase morbidity and mortality risk.¹² Sedentary behaviour is defined as any behaviour that incurs ≤1.5 METs and includes behaviours such as sitting, television watching and lying down.¹³ Sedentary behaviour is associated with numerous health risks including type 2 diabetes,¹⁴ cardiovascular disease¹⁵ and all-cause mortality.¹⁶ Given the risks of sedentary behaviour to health, recommendations for sedentary time suggest limiting discretionary sedentary time to <2 h/day and accumulating >2 h/day of light-intensity activity (ie, standing and light walking).^{17 18} Emerging evidence also suggests sedentary behaviour is associated with cognitive...