Primary headache disorders and body mass index categories: A systematic review and dose–response meta‐analysis

Objective We conducted a systematic review and dose–response meta‐analysis to investigate the association between body mass index (BMI) and primary headache disorder subtypes and to clarify the shape of this relationship. Methods PubMed and Scopus were searched from inception to September 2020. Observational studies reporting the risk estimates of primary headache disorders across categories of BMI were included. We restricted our systematic search to articles published in English. Meta‐analyses, reviews, letters to editor, case reports/case series, and s with inadequate data were excluded. We used the Joanna Briggs Institute's critical appraisal tool to assess the quality of the studies included in the meta‐analyses. One author extracted data from each study by using prespecified data extraction forms. Results In total, 41 observational studies investigating the association between BMI and different primary headache disorders with 154,044 cases and 792,500 participants were included. Among subtypes of headache disorders, the risk of migraine significantly increased in subjects who were either underweight or had obesity compared to those with normal BMI (odds ratio [OR] = 1.21, 95% confidence interval [CI]: 1.09–1.34, I2 = 6.2%; OR = 1.28, 95% CI: 1.15–1.43, I2 = 89.7%, respectively). However, there was limited evidence to support the association between BMI and the risk of other subtypes of primary headache disorders. A nonlinear association was found between BMI and migraine (p nonlinearity 29. Conclusion This meta‐analysis suggests through a nonlinear association an increased risk of migraine among individuals who are either underweight or obese. These results support the recommendation that headache disorders' prevention will benefit from weight control.