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. 2019 Jun 4;2:46. doi: 10.1038/s41746-019-0116-y

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© The Author(s) 2019

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 4 — Difference in headache days between months one and two in high and low users. The first display in the left shows the observed difference in headache days reported by each user, whereas that in the right shows the imputed difference. Users are categorized as high users if their weekly PMR use is two or more days, and as low users otherwise. Along the x axis is the difference in headache days, and along the y axis is whether the weekly PMR use is greater than or equal to 2 days