Full research paper Physical activity volume in relation to risk of atrial fibrillation. A non-linear meta-regression analysis Cristian Ricci 1 , Federico Gervasi* 2 , Maddalena Gaeta* 3 , Cornelius M Smuts 1 , Aletta E Schutte 4 and Michael F Leitzmann 5 Abstract Background: Light physical activity is known to reduce atrial fibrillation risk, whereas moderate to vigorous physical activity may result in an increased risk. However, the question of what volume of physical activity can be considered beneficial remains poorly understood. The scope of the present work was to examine the relation between physical activity volume and atrial fibrillation risk. Design: A comprehensive systematic review was performed following the PRISMA guidelines. Methods: A non-linear meta-regression considering the amount of energy spent in physical activity was carried out. The first derivative of the non-linear relation between physical activity and atrial fibrillation risk was evaluated to determine the volume of physical activity that carried the minimum atrial fibrillation risk. Results: The dose–response analysis of the relation between physical activity and atrial fibrillation risk showed that physical activity at volumes of 5–20 metabolic equivalents per week (MET-h/week) was associated with significant reduction in atrial fibrillation risk (relative risk for 19 MET-h/week ¼ 0.92 (0.87, 0.98). By comparison, physical activity volumes exceeding 20 MET-h/week wereunrelated to atrial fibrillation risk (relative risk for 21 MET-h/week ¼ 0.95 (0.88, 1.02). Conclusion: These data show a J-shaped relation between physical activity volume and atrial fibrillation risk. Physical activity at volumes of up to 20 MET-h/week is associated with reduced atrial fibrillation risk, whereas volumes exceeding 20 MET-h/week show no relation with risk. Keywords Physical activity, atrial fibrillation risk, meta-regression Received 29 January 2018; accepted 11 March 2018 Introduction Atrial fibrillation is the most common arrhythmia worldwide, causing increased risks of major cardiovas- cular events, mortality and impaired quality of life. 1,2 In particular, atrial fibrillation has been associated with increased risk of stroke and myocardial infarction and its management is a major public health challenge today. 3–6 Atrial fibrillation affects 2.3 million individ- uals in the United States. In 2005, it was estimated that its economic costs for hospitalization were about US$6.6bn per year. 7,8 The most common determinants of atrial fibrillation are increasing age, adiposity, alco- hol use and smoking. 9 Physical activity likely plays a crucial role in atrial fibrillation risk but this relation is 1 Centre of Excellence for Nutrition (CEN), North-West University, Potchefstroom, South Africa 2 Department of Clinical Sciences and Community Health, University of Milan, Italy 3 Department of Public Health, Experimental and Forensic Medicine, University of Pavia, Italy 4 MRC Unit for Hypertension and Cardiovascular Disease, Hypertension in Africa Research Team (HART), North-West University, Potchefstroom, South Africa 5 Department of Epidemiology and Preventive Medicine, University of Regensburg, Germany *The two authors equally contributed to the work. Corresponding author: Cristian Ricci, Hoffman Street, 11 2520 Potchefstroom, South Africa. Email: cristian.ricci@nwu.ac.za European Journal of Preventive Cardiology 2018, Vol. 25(8) 857–866 ! The European Society of Cardiology 2018 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/2047487318768026 journals.sagepub.com/home/ejpc