In this nationwide Korean population-based cohort study, we revealed an increased risk for developing IBD including both CD and UC in patients with migraine compared to the general population. To the best of our knowledge, it is the first study to elucidate the impact of migraine on the development of IBD. The cumulative risk of IBD showed a gradual increase following a diagnosis of migraine and, especially for CD, a steep rise after 5 years of follow-up in migraineurs. Moreover, the risk of CD was unaffected by age, sex, health behaviors, or metabolic comorbidities, while the association was prominent in male UC patients.
The total prevalence of migraine was 2.8% and the proportion of migraine in females and males was 4.2% and 1.6%, respectively. In line with our results, it is known that migraine is more prevalent in females and that subjects with migraine have higher percentages of rural residency and lower income23,24. Furthermore, metabolic syndrome, which involves a number of factors including HTN, hyperlipidemia, obesity, and insulin resistance, is more frequently reported in patients with migraine25,26. Previous studies also found an increased risk of metabolic syndrome and cardiovascular disease in patients with IBD27,28. However, even after adjusting common risk factors, we demonstrated that the risk for the development of IBD in migraineurs was significantly higher at 1.3-fold compared to the general population.
In addition, in subgroup analysis, the risk of UC in migraineurs was increased by 43% and 12% in males and females, respectively. The significant difference between sexes can be explained by the demographic prevalence of each disease. Higher risk of UC in males can be derived from lower prevalence of migraine and higher prevalence of UC. In comparison between CD and UC among migraineurs, a higher HR was found in CD, which can be supported by several prior studies showing a higher prevalence of CD in patients with migraine compared to UC29.
In previous studies, the prevalence of migraine was reported to be higher among those who were formerly diagnosed with IBD. Moreover, IBD was revealed as an independent factor of migraine disorder, suggesting an interaction between gut and brain. Conversely, there have been very few studies investigating the prevalence of IBD in subjects with or without migraine due to the comparatively low prevalence of IBD. In a cross-sectional UK Biobank study, the prevalence of IBD was not significantly higher in the migraine group than in the control group7. However, the results of our research re-establish the appropriate temporal relationship as the incidence of IBD is significantly higher in migraineurs using nationwide population-based data. Multifarious mechanisms have been proposed to describe the link between migraine and the development of IBD based on the gut–brain axis. First, proinflammatory cytokines, such as interleukin (IL)-1b, IL-6, IL-8, and tumor necrosis factor-α, have been implicated in migraine pain and are increased during migraine attack, which play a critical role in the pathogenesis of IBD30. Second, dysbiosis is known to be involved in the pathophysiology of both migraine and IBD31. Psychological and physical stressors could result in changes in the gut microbiota profile, which lead to alterations in intestinal permeability. It is well known that dietary lifestyle, especially the Western diet, is associated with the occurrence of migraine in episodic or chronic forms as well as development of IBD. Still yet to be fully revealed, diet with citrus fruit, processed meat, gluten, chocolate, coffee, and alcoholic beverages are pointed out as dietary risk factors for both migraine and IBD in several studies32–34. In addition, migraine attacks could affect the nervous system and play a particular role as a risk factor in the development of IBD. Migraine has long been implicated in impaired gastrointestinal peristalsis, which is induced by sophisticated interactions between the central, enteric, and autonomic nervous system and smooth muscles35. Furthermore, several experimental studies identified the impact of decreased gut motility on the microbial environment which is a crucial factor for the development of chronic intestinal inflammation such as IBD36,37. Finally, pharmacologic intervention for migraine such as nonsteroidal anti-inflammatory drugs (NSAIDs) has been revealed to have a role in the initiation of IBD. NSAIDs administered at higher frequency for longer duration have been associated with an increased risk of IBD, especially for CD38,39, which could be an explanation for the steep rise of cumulative probability after 5 years of follow up.
The first strength of this study was the result of increased risk of IBD in patients with migraine after adjusting for confounding variables, which has the novelty of illuminating the bidirectional gut–brain axis without confinement of cross-sectional analysis. The second strength was the high statistical power that enabled analysis for incidence of IBD in migraineurs. Despite the considerably low incidence and prevalence of IBD, this study of 10,131,193 subjects from NHIS revealed a temporal association between migraine and IBD. Third, the long period of follow-up in this cohort study for obtaining data of incidence was more than 10 years. Moreover, this study was conducted with analysis of data from a qualified public health care system that is capable of controlling the information and selection bias.
This study has several limitations. First, a detailed analysis according to the severity of migraine and IBD could not be evaluated because disease severity data of migraine and IBD was not available from the NHIS database. In addition, the impact of therapeutic modification in patients with migraine on the potential risk of IBD cannot be identified due to restriction of data acquisition. Particularly NSAIDs are well known to be effective in the treatment of migraine attacks, which can affect intestinal permeability and inflammation40. Further investigations are required to reveal the specific impact on the incidence of IBD based on the difference in severity status of migraine with or without therapeutic intervention. Second, important covariates such as dietary pattern, scale of stress, family history of IBD and comorbidities of the other gastrointestinal disorders were not included in this analysis. Because of confined adjustment, it is not clear to identify the independent association between prior migraine and risk of IBD. Despite the uncertainty of the pathophysiologic mechanism, the novelty of this study still persists because of the fact that migraine could be regarded as a predictive risk factor implying the higher incidence of IBD in nationwide population-based aspects. Finally, because of the retrospective nature, the causal relationship between migraine and IBD could not be determined.
In conclusion, the risk of IBD including CD and UC in patients with migraine was significantly higher compared to the nationwide general population. Therefore, clinicians should be aware of the potential risk of IBD in patients diagnosed with migraine especially in men for the development of UC and in migraineurs with a long disease duration for a further risk of CD. Our findings may pave the way for gut–brain axis to explore the direction and causality of these associations.