Series www.thelancet.com Published online March 25, 2021 https://doi.org/10.1016/S0140-6736(20)32160-7 1 Migraine 1 Migraine: epidemiology and systems of care Messoud Ashina, Zaza Katsarava, Thien Phu Do, Dawn C Buse, Patricia Pozo-Rosich, Aynur Özge, Abouch V Krymchantowski, Elena R Lebedeva, Krishnamurthy Ravishankar, Shengyuan Yu, Simona Sacco, Sait Ashina, Samaira Younis, Timothy J Steiner, Richard B Lipton Migraine is a neurovascular disorder that afects over 1 billion people worldwide. Its widespread prevalence, and associated disability, have a range of negative and substantial efects not only on those immediately afected but also on their families, colleagues, employers, and society. To reduce this global burden, concerted eforts are needed to implement and improve migraine care that is supported by informed health-care policies. In this Series paper, we summarise the data on migraine epidemiology, including estimates of its very considerable burden on the global economy. First, we present the challenges that continue to obstruct provision of adequate care worldwide. Second, we outline the advantages of integrated and coordinated systems of care, in which primary and specialist care complement and support each other; the use of comprehensive referral and linkage protocols should enable continuity of care between these systems levels. Finally, we describe challenges in low and middle-income countries, including countries with poor public health education, inadequate access to medication, and insufcient formal education and training of health-care professionals resulting in misdiagnosis, mismanagement, and wastage of resources. Introduction Migraine is a chronic and often lifelong disease that directly afects over 1 billion people across all world regions, cultures, and socioeconomic statuses. 1,2 This prevalence is a largely avoidable burden to global health, since efective and cost-efective treatments exist for migraine. 3,4 Evident defciencies in systems of care require urgent correction, supported by informed health-care policies. In this context, epidemiological monitoring is a powerful tool to characterise the natural course of migraine and contextualise fndings from clinic-based studies. Epidemiological studies are also key to quan- tifying the direct and indirect consequences of migraine, which enables us to understand the efect of migraine on people with the disorder and on their families, colleagues, employers, and society. In this Series paper, we provide an overview of the epidemiology and global burden of migraine to increase awareness and understanding of them as a prerequisite for remedial action. We discuss the current structure and practices of migraine care, including specifc challenges in low and middle-income countries. We also pro- vide recommendations to standardise epidemiological monitoring, improve health-economic assessment, and tailor best practices within systems of care to local needs and resource availability. Published Online March 25, 2021 https://doi.org/10.1016/ S0140-6736(20)32160-7 This is the first in a Series of three papers about migraine Danish Headache Center, Department of Neurology, Rigshospitalet Glostrup, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark (Prof M Ashina MD, T P Do MD, S Younis MD); Danish Knowledge Center on Headache Disorders, Glostrup, Denmark (Prof M Ashina); Department of Neurology, Azerbaijan Medical University, Baku, Azerbaijan (Prof M Ashina); Department of Neurology, Evangelical Hospital Unna, Unna, Germany (Prof Z Katsarava MD); Department of Neurology, University of Duisburg-Essen, Essen, Germany (Prof Z Katsarava); EVEX Medical Corporation, Tbilisi, Georgia (Prof Z Katsarava); Department of Neurology, IM Sechenov First Moscow State Medical University, Moscow, Russia (Prof M Ashina, Prof Z Katsarava); Department of Neurology, Albert Einstein College of Medicine, Bronx, NY, USA (Prof D C Buse PhD, Prof R B Lipton MD); Headache Unit, Neurology Department, Hospital Universitari Vall d’Hebron, Barcelona, Spain (P Pozo-Rosich MD); Headache and Neurological Pain Research Group, Vall d’Hebron Research Institute, Department of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain (P Pozo-Rosich); Department of Neurology, Mersin University, School of Medicine, Mersin, Turkey (Prof A Özge MD); Headache Center of Rio, Rio de Janeiro, Brazil (Prof A V Krymchantowski PhD); Department of Neurology, International Headache Centre Europe-Asia, the Ural State Medical University, Key messages • Migraine is ubiquitous and prevalent, impairing the health and quality of life of many people, with profound efects on their families, colleagues, and society • Migraine is the leading cause of disability worldwide in people younger than 50 years (particularly in women) and a major cause of tremendous losses to the global economy • Despite these facts, serious defciencies are reported worldwide in the professional and political awareness of migraine and resource allocation to its management • Primary-care professionals are the principal providers of health services for migraine; specialist referral can be needed for patients with treatment resistance, atypical features, or comorbidities • Epidemiological studies should continue to fll geographical and other knowledge gaps, using standardised consensus-based methodology to enable comparative assessments between countries • Methods to assess the range of indirect consequences of migraine (such as family efect, lost career potential) should be developed and yield a full account of migraine- attributed burden, to improve informed health-care policies • More research should identify best clinical practices and care strategies within structured headache services and assess their efectiveness, reach, and cost-efectiveness • In low and middle-income countries, concerted eforts should be made to fnd health-care solutions to migraine that are tailored according to local needs, infrastructure, and resources, of which training and education are key Search strategy and selection criteria We searched MEDLINE (from database inception to Jan 1, 2020), and Embase (from database inception to Jan 1, 2020) for original research articles, systematic reviews, and meta-analyses. We used the search term “migraine” in combination with the terms “epidemiology”, “burden”, “health economics”, “systems of care”, “specialist care”, and “primary care”. We mainly selected publications in the past 5 years but did not exclude commonly referenced and highly regarded older publications. We also searched the reference lists of articles identifed by this search strategy and selected those we judged relevant.