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. 2019 Apr 2;9(4):e027701. doi: 10.1136/bmjopen-2018-027701

Figure 1.

Figure 1

A schematic illustrating the participant selection process used in the present study. Of a total of 1 125 691 participants, 41 585 participants with migraine were matched with 166 340 control participants for age, group, sex, income level, region of residence and medical histories.