Review Cephalalgia 2022, Vol. 42(13) 1387–1396 Migraine-attributed burden, impact and ! International Headache Society 2022 disability, and migraine-impacted quality Article reuse guidelines: sagepub.com/journals-permissions of life: Expert consensus on definitions DOI: 10.1177/03331024221110102 journals.sagepub.com/home/cep from a Delphi process Timothy J Steiner1,2, Gisela M Terwindt3, Zaza Katsarava4,5,6, Patricia Pozo-Rosich7,8 , Andreas R Gantenbein9,10,11 , Sarah L Roche12, Grazia Dell’Agnello13 and Cristina Tassorelli14,15 Abstract Background: Migraine-attributed burden, impact, disability and migraine-impacted quality of life are important concepts in clinical management, clinical and epidemiological research, and health policy, requiring clear and agreed definitions. We aimed to formulate concise and precise definitions of these concepts by expert consensus. Methods: We searched the terms migraine-attributed burden, impact, disability and migraine-impacted quality of life in Embase and Medline from 1974 and 1946 respectively. We followed a Delphi process to reach consensus on definitions. Results: We found widespread conflation of concepts and inconsistent terminology within publications. Following three Delphi rounds, we defined migraine-attributed burden as “the summation of all negative consequences of the disease or its diagnosis”; migraine-attributed impact as “the effect of the disease, or its diagnosis, on a specified aspect of life, health or wellbeing”; migraine-attributed disability as “physical, cognitive and mental incapacities imposed by the disease”; and migraine-impacted quality of life as “the subjective assessment by a person with the disease of their general wellbeing, position and prospects in life”. We complemented each definition with a detailed description. Conclusion: These definitions and descriptions should foster consistency and encourage more appropriate use of currently available quantifying instruments and aid the future development of others. Keywords Migraine, burden, impact, disability, quality of life, definitions, Delphi, expert consensus Date received: 8 April 2022; revised: 17 May 2022; accepted: 26 May 2022 9 Department of Neurology, ZURZACH Care, Bad Zurzach, Switzerland 10 Neurological Practice, Neurologie am Untertor, Bülach, Switzerland 1 11 Department of Neuromedicine and Movement Science, NTNU Department of Neurology, University Hospital Zurich, Zürich, Norwegian University of Science and Technology, Trondheim, Norway Switzerland 2 12 Division of Brain Sciences, Imperial College London, London, UK Eli Lilly and Company, Cork, Ireland 3 13 Department of Neurology, Leiden University Medical Center, Leiden, Eli Lilly Italia SpA, Sesto Fiorentino, Florence, Italy 14 The Netherlands Department of Brain and Behavioral Sciences, University of Pavia, Pavia, 4 Christian Hospital Unna, Unna, Germany Italy 5 15 Department of Neurology, University of Duisburg-Essen, Essen, Headache Science & Neurorehabilitation Center, IRCCS Mondino Germany Foundation, Pavia, Italy 6 EVEX Medical Corporation, Tbilisi, Georgia 7 Headache Unit, Neurology Department, Vall d’Hebron University Corresponding author: Hospital, Barcelona, Spain Grazia Dell’Agnello, Eli Lilly Italia SpA, Via A. Gramsci, 731, 50019 Sesto 8 Headache Research Group, Vall d’Hebron Research Institute, Fiorentino, Florence, Italy. Universitat Autonoma de Barcelona, Barcelona, Spain Email: dell_agnello_grazia@lilly.com 1388 Cephalalgia 42(13) Introduction which this is one, with members then deciding in which initiatives they wished to participate. Migraine impairs health, disables those affected, and All eight authors constituted the expert panel for impacts their wellbeing. Evidence of this is supplied this work. TJS, GMT, ZK, PPR, ARG and CT were by many sources (1–10). Among these, the Global members of the multi-stakeholder working group and Burden of Disease (GBD) studies have reiteratively participated as headache specialists with expertise in ranked migraine as the second highest single cause of clinical practice, research, headache terminology and years lived with disability (YLDs) worldwide (8–10). nosography, and/or headache epidemiology. GDA The evidence from GBD is particularly compelling, and SLR brought expertise in clinical research and/or but in the context of our study – concerned with defi- headache terminology and nosography, and contribut- nitions – it calls for considered interpretation. While ed to the project methodology. GBD’s stated purpose is to estimate burden attributed to all diseases, enabling these to be ranked for the pur- pose of informing health policy (11), the expression of Literature search and screening of records non-fatal burden in YLDs is not conceptually coherent. Two authors (GDA and SLR), along with one other Firstly, non-fatal burden is not wholly quantifiable by employee of Eli Lilly and Company outside the author- a measure of disability. Secondly, YLDs are not in any ing team (AF – see acknowledgements), searched case a measure of disability but of disease-attributed Embase and Medline for publications addressing any health states ranked according to public preferences of migraine-attributed burden, impact or disability, for one health state over another (12). YLDs better and migraine-impacted quality of life, published from reflect lost health due to disease (12), which may 1974 or 1946, respectively, up to May 2021. Details of indeed approximate to the concept of burden of disease, the search terms and syntax are provided in but the latter is a much more complex construct than Supplementary Material 1. Relevant reviews, editori- disability, and certainly not synonymous with it. als, concept papers and commentaries were identified In the vocabulary of migraine, burden, disability, from this search through the following procedures. impact and quality of life are important concepts. Records were screened by GDA and SLR to remove They are quantifiers, guiding clinical management of duplicates and select those including the terms the disorder and informing clinical and epidemiological “burden”, “impact”, “disability” and/or “quality of research into migraine and health policy (13,14). There life” in the title and/or abstract. From their full texts, is a complex relationship between them, which is to publications were selected that focused on any of these some extent hierarchical, with burden correctly associated with migraine. Primary research publica- regarded as an overarching construct subsuming the tions, and papers focused on financial cost (at individ- others (13). ual or societal levels), on comorbidities of migraine as However, the literature addressing these concepts predictors of disability or burden rather than migraine often distinguishes poorly or not at all between them, itself, or on validation of scales, were excluded as out- sometimes using the terms as though synonymous. side the scope of our study. Uncertainties were resolved Whatever conceptual confusion and disagreements lie by discussion and agreement between these authors. behind this, they need to be resolved for the benefit of Selected papers were reviewed in full by GDA and care, research and health policy. To this end, the terms SLR. Each was screened for descriptions of migraine- require clear and credible definitions, whether they are attributed burden, impact and disability, and migraine- to be applied at individual or population levels. These impacted quality of life. Listings were generated, per do not currently exist. Our objective, therefore, was to paper and per concept, of the topics referenced as part formulate such definitions by expert consensus. of each concept’s description, and findings were sum- marised, per concept, as lists and frequencies of across Methods all selected papers. Panel of experts Formulation of definitions Prior to initiation of this work, Eli Lilly and Company We used the widely accepted Delphi method (15) to established a ten-member multi-stakeholder working achieve consensus between all eight authors. Since the group, including experts in various aspects of headache covid-19 pandemic prevented travel, we met virtually medicine, representatives of patient advocacy groups and conducted rounds by email. and policy makers, to support actions to improve man- For the first round, lists of candidate items identified agement of migraine in Europe. The group identified by GDA and SLR through the literature search and to barriers to care and proposed remedial initiatives, of be considered in the definitions of each concept were Steiner et al. 1389 pre-circulated (Supplementary Material 2, Table S1). Results Each member of the expert panel scored each item with regards to correspondence to the concept in ques- Screening of records from the literature search tion (1: does not correspond; 2: relevant but not criti- The initial search yielded 1,584 records. Screening of cal; 3: directly corresponds and critical) and to clarity titles and abstracts reduced these to 280, of which 240 (1: unclear; 2: needs revision; 3: clear). There was were excluded upon inspection of their full texts opportunity in this round to comment. Responses (Figure 1). From the texts or reference lists of 39 of were sent to a facilitator (PF – see acknowledgements) the 40 remaining publications (full text was unavailable outside the authoring team who anonymised them for one), an additional 7 relevant publications were before sending to SLR for collation. Items were identified. A total of 46 papers were therefore included retained when there was >70% agreement on corre- in the analyses, published over 28 years (1994–2021) spondence (including scores of 2 and 3), or otherwise omitted. This agreement level was closely aligned with (3,7,8,18–60) (Figure 1). Of these 46, 42 (91%), 36 (78%), 44 (96%) and the median threshold reported across 25 Delphi studies (16) and was used in a previous Delphi study to achieve 28 (61%) respectively offered descriptions of consensus on another definition (17). Issues around migraine-attributed burden, impact, and disability, clarity, and comments suggesting items that might be and migraine-impacted quality of life. The descriptions missing, were addressed by rephrasing and revising were notably characterised by inconsistency and, to according to this feedback. some extent, by confusion. Descriptions of migraine- The second Delphi round presented proposed defi- attributed burden included references to impact, dis- nitions, formulated by GDA and SLR, that best repre- ability and quality of life in 45%, 74%, and 38% of sented all authors’ expressed opinions. Participants cases respectively. This might be expected if burden is responded “yes” or “no”, in agreement or otherwise considered as an overarching construct, but the with each proposed definition (Supplementary descriptions of migraine-attributed impact and disabil- Material 2, Table S2). As in Round 1, responses were ity and of migraine-impacted quality of life commonly sent to a facilitator (PF – see acknowledgements) out- included references to each other (Figure 2A), indicat- side the authoring team who anonymised them before ing conflation. Ambiguous terminology (for example, sending to SLR for collation. SLR shared the anony- GBD’s use of “disability” for lost health, referred to mised results with all authors. earlier) was a major complicating factor. Overlap In the third round, conducted as a virtual group between concepts was clearly evident in the specific discussion with follow-up email correspondence, dis- items ascribed to each concept in the various publica- senters in the second round (those responding “no”) tions (Figure 2B). justified and defended their responses in open forum Aside from conflation and overlap, publications to resolve disagreements through debate and thereby ranged widely in item inclusion. For example, 62% of reach consensus (Supplementary Material 2, Table S3). reviews that provided descriptions of migraine-attributed 1,304 records excluded – Duplicates 1,584 potentially eligible records – Studies on primary research and/or – Identified through database searching focused on cost, comorbidities of migraine, validation of scales 240 records excluded – Studies on primary research and/or 280 records retained for screening focused on cost, comorbidities of migraine, validation of scales 40 publications Full text of 1 record unavailable 7 additional reviews – Identified from reading or reference lists 46 publications included in the analyses Figure 1. Screening of records from the literature search. 1390 Cephalalgia 42(13) Concepts/Topics referenced: Burden Impact Disability Quality of Life (a) Burden NA Impact NA Disability NA Quality of life NA (b) Society Individual/Personal Productivity/Absenteeism/Presenteeism Occupational or household work/Career/Employment Economy Healthcare systems/Societal healthcare costs/HRU GBD Family life/Family members/Relationships Social life/Leisure time lctal/Migraine attack Physical function/Functional impairment Interictal Comorbidities Disease or headache severity/Pain Mental health/Overall health/Wellbeing/Emotion/Mood Medication overuse Co-worker/Employer Headache or attack frequency Caregiver Individual costs WHO/WHO ICF Academic life/Education Environmental factors Colour gradient corresponding to percentages 0 10 20 30 40 50 60 70 80 Figure 2. Concepts and topics (and frequencies thereof) referenced in the literature to describe migraine-attributed burden, impact, and disability, and migraine-impacted quality of life. (a) Publications referencing burden, impact, disability and/or quality of life as parts of each other’s descriptions and (b) Publications referencing specific topics in their descriptions of each concept. NA: Not Applicable; GBD: Global Burden of Disease (study); HRU: health resource utilisation; WHO ICF: World Health Organization International Classification of Functioning, Disability and Health. burden referred to “society”, whereas 24% referred to “ictal/migraine attack”, whereas 7% referred to “interictal” as part of this concept. Among reviews that “headache or attack frequency” as a part of this con- provided descriptions of migraine-attributed impact, cept (Figure 2B). 61% referred to “occupational or household work/ career/employment”, whereas 39% referred to Proposed definitions and descriptions “society” as part of this concept. Among reviews that provided descriptions of migraine-attributed disability, The second round of the Delphi process achieved 45% referred to “occupational or household work/ >70% agreement (our predetermined target: see career/employment”, whereas 9% referred to Methods) on all definitions (Supplementary Material “environment” as part of this concept. Regarding 2, Table S2). In the third round, which led to 100% migraine-impacted quality of life, 21% of reviews that consensus on all, we recognised the need for definitions provided descriptions of this concept referred to to be not only precise but also memorable, pursuing the Steiner et al. 1391 purpose of obviating misunderstandings and future (family, friends, colleagues, schools, employers) of inconsistencies (Supplementary Material 2, Table S3). those who have it (13). Fifth, some aspects of burden This led to development of concise definitions, each fall on society itself: the opportunity costs of resource complemented with a detailed explanatory description expenditure on treating the disease, and the societal (Table 1). losses due to workforce diminution and reduced Gross Domestic Product. While burden as a construct embraces all negative Discussion consequences of the disease, and is defined as the sum- In this study we used a Delphi process achieving 100% mation of these, there are challenges that are likely to consensus in formulating new definitions, each with remain insuperable in recognising them all, and in mea- complementary descriptions, of migraine-attributed suring many of those that are recognisable. A single burden, migraine-attributed impact, migraine- metric wholly quantifying burden is not feasible, attributed disability and migraine-impacted quality of either at individual or at population level. While life. What was the need for these, and what purposes GBD makes a valiant effort at quantifying lost health might they serve? We began by searching the literature attributable to migraine (which in future iterations may addressing these constructs and concepts, finding it be expressed as healthy life years [HLYs] lost rather inconsistent and confused. Concepts were often con- than YLDs), its estimates are based on time in symp- flated, and terminology used ambiguously or as tomatic state: it does not capture interictal burden, though synonymous, while being fundamentally impor- cumulative burden or burden falling on others (61). tant in understanding how migraine affects people and populations (13). They are crucial in managing the dis- Migraine-attributed impact order, in describing it, and in needs assessment inform- Our definition and description of migraine-attributed ing healthcare policy and allocation of healthcare impact similarly acknowledge contributions both from resources. Uncertainties in what they mean, and what the disease itself and from its diagnosis. Crucially, they embrace, affect all of these adversely, while mis- migraine-attributed impact is a singular effect on a sin- informing the development of treatments, the construc- gular aspect of life, health or wellbeing, and the term tion of patient-reported and other outcome measures, has no meaning unless the latter is specified. Migraine and clinical trial design. The benefits of clear and may and often does have multiple effects on many of unambiguous definitions should accrue to all of these. these aspects, either simultaneously or in temporal sequence, but it is essential to the concept that each Migraine-attributed burden of these is a separate impact, distinct from any other We continued to view migraine-attributed burden as an (although associations between them are highly likely). overarching construct, subsuming migraine-attributed Like burden, some impacts are experienced not so impact(s) and disability, and migraine-impacted quality much by the person with migraine but by others, of life. Several features of our definition, and the through their relationships with and attitudes towards accompanying description, call for comment. First, that person. Like burden, some impacts – on educa- there are negative consequences contributing to tion, employment, or family life, for example – are last- burden that arise not from the disease itself but from ing or cumulative, fully expressed only in future carrying its diagnosis. The latter are due in part to outcomes. At the societal level, there are impacts on stigma, but there is burden simply in being a patient, healthcare demand and supply, and on workforce pro- in need of healthcare that must be sought (patienthood) ductivity and economy. (13). Second, migraine-attributed burden arises both Because impact is a singular effect, it is, potentially, ictally and interictally, in the former case, and to much more readily measurable – in the units that quan- some extent the latter, varying between individuals tify whatever aspect of life, health or wellbeing is according to frequency, duration and severity of impacted (so long as this is itself measurable). Migraine-attributed impact on productivity, for exam- attacks. Third, there are negative consequences of ple, can be and often is quantified as lost productive migraine that are cumulative, and which may outlast time, but it could also be measured in units of output. the currency of the disease: missed opportunities in education, damaged prospects, lack of fulfilment in career or family (13). Fourth, there are negative con- Migraine-attributed disability sequences of the disease borne by others than those Our definition and description of migraine-attributed who have it, who are in the social environments disability recognise that physical, cognitive and/or 1392 Table 1. Final consensus definitions and detailed descriptions of the four concepts. Concept Definition Detailed description Migraine-attributed The summation of all negative The negative consequences of the disease include those occurring during or between migraine burden consequences of the disease or attacks, some that are borne by others than those with the disease, some that are cumulative its diagnosis. over time and some that outlast the currency of the disease. Some negative consequences for the person with the disease may arise from the diagnostic label rather than the disease itself. Migraine-attributed burden is consequently expressed at individual, interpersonal-social, and societal levels. Migraine-attributed The effect of the disease, or its diagnosis, The disease, or its diagnosis, may affect: impact on a specified aspect of life, health or  the life, health, capabilities, aspirations, opportunities, work and production, prosperity, wellbeing. position in life, recreation or general wellbeing of the person with the disease;  relationships with others and the attitudes of those around them towards the person with the disease;  and, when multiplied by numbers of people with the disease, social groups, community, or society more generally. Migraine-attributed impact is a singular effect on any one of these. When there are effects on more than one, each is a separate impact, distinct from any other, although associations between them are highly likely. Depending on its nature, migraine-attributed impact may be transient, lasting and/or cumulative. Migraine-attributed Physical, cognitive and mental incapacities Physical, cognitive and mental incapacities imposed by the disease are influenced (moderated or disability imposed by the disease. exacerbated) by the individual’s personal characteristics and expressed in the context of that individual’s environment, hindering, impairing or preventing participation in or completion of day-to-day activities as would be expected if the individual were free of the disease. Migraine-attributed disability is expressed at individual level. Migraine-impacted The subjective assessment by a person Subjective assessment by a person with the disease of their general wellbeing, position and quality of life with the disease of their general prospects in life takes due account of all aspects of their health (including the disease) and of their wellbeing, position and prospects in life. physical, mental and social functional abilities. Migraine-impacted quality of life is expressed at individual level but may be summarised across populations. In either case, it has meaning only in comparison with normative values of quality of life. Cephalalgia 42(13) Steiner et al. 1393 mental incapacities are imposed by the disease. makes, or should make, no direct attribution to Further, our description acknowledges that these inca- migraine (no sound basis exists for doing this). For pacities are influenced by the individual’s personal this last reason, it has meaning only in comparison characteristics, and are expressed in the context of with normative values. It may be summarised across that individual’s environment (62). Incapacities may populations, and in large groups the difference between be imposed during the attack, directly by the symptoms means of normative and migraine-impacted values can of it (pain, visual disturbances and photophobia in par- be fairly attributed to the disease. ticular), or between attacks, for example by interictal anxiety leading to the disability imposed by avoidance Strengths and limitations behaviour. Unlike burden and impact, disability is expressed One limitation of this work was the small number of only at individual level. Because of its multifaceted experts contributing to these definitions and descrip- nature and the influences of personal characteristics tions. Another was that people with migraine were and environment, migraine-attributed disability is not not involved or consulted. The major strength is that readily measured and, like burden, cannot be the definitions and descriptions were formulated to be quantified by a single metric. YLDs, as noted earlier, relevant to care, research and health policy. are a measure of lost health rather than disability. The World Health Organization International Next steps Classification of Functioning, Disability and Health (WHO ICF) is a system for describing disease- We recognise that these definitions are a starting point. attributed disability taking account of personal charac- The next steps require broader input to assess their teristics and environment, but requiring complex comprehensibility, acceptability and comprehensive- question sets (62). No such set exists for migraine, ness. Using different methodologies, these steps must although the methodology for creating one has been involve experts from other parts of the world – in head- described (63). ache medicine and in public health – and be informed Disability translates into secondary impacts: undone by the views of people who bear the burden of day-to-day activities; missed work or schooling; undis- migraine. Alignment across these various constituen- charged household, community or societal responsibil- cies, once achieved, will provide a far better basis ities; abandoned social activities or recreational than we have now for scrutinising the available instru- endeavours; interrupted care for children and family ments, and establishing just how well they measure members. All of these become parts of migraine- what they claim to on the one hand and what matters attributed burden (13), but they are not, themselves, on the other. any part of migraine-attributed disability. Conclusions Migraine-impacted quality of life The literature in the field of migraine shows inconsis- There is a certain tautology about migraine-impacted tencies, conflation, overlap and confusion in the termi- quality of life, since, as the term implies, it is the con- nology used to describe migraine-attributed burden sequence of an impact. Conceptually, however, it has unique importance among the many components of and components of it expressed as migraine- migraine-attributed burden, deserving of recognition attributed impact, migraine-attributed disability and per se. Our definition and description recognise three migraine-impacted quality of life. Our definitions and distinctions from the concepts of impact and disability. complementary descriptions, arrived at by expert con- First, it is wholly subjective, and therefore not exter- sensus, are a starting point in fostering consistency in nally verifiable. Second, it is an evaluation not of the the future. Ultimately, the benefits should be expressed impact itself but of the remnant after it (what is left, in more appropriate use of currently available quanti- not what is taken away). Third, it is an assessment of fying instruments and the future development of what is, taking account of the disease as only one others, with better care and monitoring of patients, among all factors of influence, not of what might be less ambiguity in clinical and epidemiological research, were it not for the disease: at individual level, it and more reliably informed health policy. 1394 Cephalalgia 42(13) Public health relevance • The literature describing migraine-attributed burden is inconsistent in its use of “burden”, “disability”, “impact” and “quality of life”, often conflating their underlying concepts. • These inconsistencies have intruded into quantifying instruments, so that needs assessment, and health policy are unreliably informed. • Consensus definitions and detailed descriptions of these terms, formulated through a Delphi process, are offered as a future remedy. Acknowledgements funding for clinical trials from Alder, Amgen, Electrocore, The authors thank Angeles Flores, an employee of Eli Lilly Eli Lilly, Lundbeck, Novartis and Teva. She is the founder and Company, and Daniela G€ odderz, an employee of of www.midolordecabeza.org, the Honorary Secretary of the Executive Insight, for their support with the literature International Headache Society. She is on the editorial board search. We also thank Janet Ford, an employee of Eli Lilly of Revista de Neurologia, an associate editor for Cephalalgia, and Company, for support with development of an earlier Headache, Neurologia, Frontiers of Neurology and advisor for version of this article and with formulating the input to The Journal of Headache and Pain. She is also a member of Delphi Rounds 1 and 2. We are grateful for contributions the Clinical Trials Guidelines Committee and Scientific from David Ayer and Philana Fernandes, employees of Eli Committee of the International Headache Society and has Lilly and Company, in, respectively, providing support with edited the Guidelines for the Diagnosis and Treatment of formulating the input to Delphi Rounds 1 and 2 and ano- Headache of the Spanish Neurological Society. ARG reports nymising responses. financial support for speaking, consultancies, education, research, or travel from Allergan, Almirall, Amgen, Biogen, Availability of data and materials Biomed, Curatis, Eli Lilly, Grünenthal, Lundbeck, Novartis, Teva Pharma. SLR is a full-time employee of Eli Lilly and Details of the literature search strategies can be found in Company. GDA is a full-time employee and minor stock- Supplementary Material 1. holder of Eli Lilly and Company. CT received honoraria for the participation in advisory boards or for lecturing Authors’ contributions from: Allergan/Abbvie, Eli Lilly, Lundbeck, Novartis, Teva All authors contributed to the conception or design of the and Medscape. Her Institution has received payments for work. TJS, GMT, PPR, ARG, SLR, GDA and CT contrib- clinical trials for Allergan/Abbvie, Eli Lilly, Lundbeck, uted to the acquisition, analysis or interpretation of data for Novartis and Teva. CT has no ownership interest and does the work. All authors contributed to drafting of the work or not own stocks of any pharmaceutical company. CT is on the revising it critically for important intellectual content. All editorial board of The Journal of Headache and Pain and authors approved the final version to be published and Cephalalgia. TJS, GMT, ZK, PPR, ARG and CT did not agreed to be accountable for all aspects of the work. receive fees from Eli Lilly for the activity related to this manuscript. Declaration of conflicting interests The authors declared the following potential conflicts of Funding interest with respect to the research, authorship, and/or pub- The authors disclosed receipt of the following financial sup- lication of this article: TJS reports personal fees from Eli port for the research, authorship, and/or publication of this Lilly. GMT reports consultant fees from Amgen, Eli Lilly, article: This work was funded by Eli Lilly and Company. Lundbeck, Novartis and Teva, and has received grant sup- port from the Dutch Research Council, Dutch-Brain ORCID iDs Foundation, the Dutch Heart Foundation, IRRF, and Patricia Pozo-Rosich https://orcid.org/0000-0003-0796- Dioraphte. ZK has been a speaker and/or consultant, and/or 4702 received research support from Allergan, Amgen/Novartis, Andreas R Gantenbein https://orcid.org/0000-0001-5686- Eli Lilly, Merck and Teva. PPR has received honoraria as a 0200 consultant and speaker for Allergan/AbbVie, Almirall, Cristina Tassorelli https://orcid.org/0000-0003-1513-2113 Biohaven, Chiesi, Eli Lilly, Lundbeck, Medlink, Medscape, Novartis and Teva. Her research group has received research grants from Allergan/AbbVie, AGAUR, la Caixa founda- References tion, EraNET Neuron, FEDER RIS3CAT, Migraine 1. Woldeamanuel YW and Cowan RP. Migraine affects 1 in Research Foundation, Instituto Investigaci on Carlos III, 10 people worldwide featuring recent rise: A systematic MICINN, Novartis, Teva, and PERIS, and has received review and meta-analysis of community-based studies Steiner et al. 1395 involving 6 million participants. J Neurological Sci 2017; 15. Dalkey NC. An experimental study of group opinion: 372: 307–315. The Delphi Method. Futures 1969; 1: 408–426. 2. Steiner TJ, Stovner LJ, Katsarava Z, et al. The impact of 16. Diamond IR, Grant RC, Feldman BM, et al. 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