New research extends upon the Global Burden of Disease study, finding that the prevalence of migraine has increased over time.
Headache disorders are among the most common and disabling health conditions in the world. Knowing the prevalence of these disorders is crucial to forecast health service needs and to understand where to direct healthcare resources. However, efforts to estimate the prevalence and burden of headache disorders are faced with methodological challenges and geographic differences.
Now, researchers led by Lars Jacob Stovner from the Norwegian University of Science and Technology, Trondheim, Norway, have reviewed 357 prevalence studies in order to update global prevalence estimates for headache disorders, including all headache, migraine, and tension-type headache. The investigators also examine how various methodological factors influence these estimates.
The group estimates that the global prevalence of an active headache disorder is 52%, meaning that one in two people reported some kind of headache in the past year. This estimate is higher than the most recent Global Burden of Disease estimate, published in 2019.
The authors also find that almost 15% of the world’s population have a headache on any given day, with almost half of those being a migraine headache. Roughly 5% had a headache at least 15 days a month. Migraine was also found to increase in prevalence over the years.
The study further reveals that a number of methodological factors influenced prevalence estimates, though some of those factors were not significant.
“The study considers many methodological factors that influence estimates of prevalence and burden, providing important advice for future studies,” wrote Richard Lipton, Albert Einstein College of Medicine, New York, US, in an email to Migraine Science Collaborative. Lipton is a headache researcher with expertise in migraine epidemiology and population health but was not involved in the current study.
“This updated review does much to clarify the prevalence and burden of headache overall and the most important types of headaches – migraine, tension-type headache, and headache on more than 15 days per month,” Lipton continued.
The study appeared in The Journal of Headache and Pain on April 12, 2022. (Also see MSC related data visualization.)
Time for an update
Millions of people around the world are affected by headache disorders such as migraine. The Global Campaign against Headache, a collaboration between Lifting the Burden, a London-based charitable nongovernmental organization, and the World Health Organization, has played a key role in bringing attention to the importance of estimating the prevalence and burden of these disorders.
Stovner, lead author of the current study, has been involved with the Global Campaign against Headache for several years, with the Norwegian University of Science and Technology serving as the academic base of the campaign.
“Part of the campaign was to publish all of the evidence on headache prevalence and burden, which we did in 2007,” Stovner told MSC. “Since then, there have been many new papers published in the area, and the Global Burden of Disease study has also become very interested in headache.” The Global Burden of Disease is a study that examines prevalence, premature death, and disability for hundreds of diseases and injuries, throughout the world, beginning in 1990.
Stovner continued, “When the Global Burden of Disease study was first published in 2000, migraine was the 19th most disabling disorder. From 2016 onwards, it has been the second most disabling disorder worldwide. And it’s not because the prevalence of migraine has increased so much. It’s mostly because we have been better at presenting the data.”
Key to determining the prevalence and burden of any condition is having access to multiple data sources, such as epidemiological studies, hospital data, and official statistics. However, epidemiological studies are the only available source of data in the headache field. Further complicating matters is that while headache data are now available for many countries, methodological differences between studies are common, resulting in substantial variation in prevalence estimates between, and occasionally within, countries.
So, Stovner and colleagues were keen not only to update their previous review on the global prevalence of headache, but also to explore, for the first time, how methodological differences between studies might influence prevalence estimates.
“We thought it would be worthwhile to validate what the Global Burden of Disease has found by using a somewhat simpler methodology,” explained Stovner. “But perhaps the most important thing we wanted to do with this new paper was to look at how the methodology of the prevalence studies influences the results we get.”
The results are in
So, Stovner and his colleagues did an extensive literature search, which ultimately resulted in 357 published papers that met the authors’ criteria for inclusion in their current study. Most articles came from the Global Burden of Disease High Income “superregion,” which includes countries such as the United States, Canada, Japan, Australia, Germany, and the United Kingdom.
Globally, an active headache disorder was present in 52% of the population. That represents an increase in the prevalence of headache disorders from Stovner and colleagues’ 2007 review, which came in at 46%. This figure is also higher than the 35% prevalence reported by the 2019 iteration of the Global Burden of Disease study, though that finding has a relatively simple explanation.
“The headache category in the Global Burden of Disease study is just the sum of migraine and tension-type headache,” Stovner said. “But in the headache prevalence we record, that may include more than those two disorders.”
When considering the specific types of headache disorders, the prevalence of tension-type headache was 26%, migraine was at 14%, and headache on 15 or more days in a month was at 4.6%. The prevalence of tension-type headache and migraine was similar to what the 2019 Global Burden of Disease study reported (27% and 15%, respectively).
Just as the prevalence of active headache increased since the authors’ initial 2007 review, so did the prevalence of migraine (from 11% to 14%) and headache on 15 days or more per month (from 3% to 4.6%). However, the prevalence of tension-type headache decreased from 42% to 26%.
The finding that 4.6% of the population reported headache on 15 days or more each month was striking but encouraging, according to Lipton, as this information will help direct appropriate treatment to this group of people.
“Nearly 1 in 20 people have exceptionally frequent headaches. This group has been shown to have higher levels of disability, underemployment or unemployment, and lost productive time at work. The high attack frequency and disability make this group particularly attractive for healthcare interventions designed to reduce burden,” Stovner explained.
Methodology sometimes matters
When the researchers turned to the influence of methodological factors on the prevalence estimates, they found that several factors contributed to variation in the estimates, though many of those factors were not statistically significant.
Among the significant factors were the study publication year, sample size, inclusion of a probable diagnosis, and the wording and types of questions used to determine the presence of headache.
“All future studies should use validated questionnaires, describe the screening question verbatim, and explain how they deal with definite and probable diagnoses. Ideally, future prevalence estimates from all parts of the world will be derived from studies performed in a relatively standardized way, in accordance with published recommendations,” Stovner and colleagues concluded in their article.
Another area of concern relates to an imbalance between population density and where headache and migraine research is undertaken. Although half of the world’s population live in South Asia, SouthEast Asia, East Asia, and Oceania – superregions including large countries such as India, Pakistan, and China, as well as smaller countries like Fiji and Samoa – only 9% of headache prevalence studies come from those regions. The small number of studies from those areas makes incidental findings or inaccurate prevalence estimates more likely.
“A big part of the Lifting the Burden activities was to perform studies in countries such as those,” said Stovner. “However, many of these countries have limited resources, which they are using for what they perceive as the most severe disorders that must be treated before headache, such as infectious diseases.
“That said, we find a lot of headache disorders in these countries. That means these people not only suffer from all the diseases of poverty but also headache,” said Stovner.
For his part, Lipton appreciates the work undertaken over the last two decades to shine a light on the burden of headache disorders.
“The ranking of migraine as the world’s second most disabling disorder by the Global Burden of Disease study has literally and figuratively helped place migraine on the public health map as an urgent priority for research and treatment,” Lipton wrote to MSC.
The current study refines that map and could bring even more visibility to it. Ideally, this would increase the amount of attention paid to headache disorders and better direct healthcare resources to the people and regions that need them the most.
Lincoln Tracy, PhD, is a researcher and freelance writer based in Melbourne, Australia. Follow him on Twitter @lincolntracy.
The global prevalence of headache: an update, with analysis of the influences of methodological factors on prevalence estimates. Stovner et al. J Headache Pain. 2022 Apr 12;23(1):34.
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
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