Comorbidities of primary headache disorders: a literature review with meta-analysis

Table 1 Overview of selected studies

Main headache disorder by study	No. Studies	No. Patients	% of Females Median (IQR)	Average age Median (IQR)	Average monthly headaches Median (IQR)
Migraine only ^a	100	3,455,438	79.7 % (72.6–91.5 %)	39.6 (36.4–46.0)	7.1 (4.9–9.8)
TTH only ^b	5	14,100	53.0 % (53.0-60.5 %)	42.7 (42.7–42.8)	1.9 (1.5-2.0)
CH only ^c	5	594	25.8 % (18.2–62.2 %)	49.1 (46.1–53.0)	NA
Mixed Studies^d	29	724,072	77.4 % (72.5–89.2 %)	39.9 (37.9–42.9)	9.7 (4.6–13.8)
All studies	139	4,185,906	77.8 % (71.4–90.0 %)	40.4 (36.9–46.0)	7.0 (4.0-10.1)

Note. ^aAmong patients included in studies on migraine only, 48,650 (1.4 %) had episodic migraine, 4,651 (0.1 %) had chronic migraine, and 3,402,137 (98.5 %) had migraine not otherwise specified. In total, 13,765 (0.4 %) were enrolled in clinical studies and 3,441,673 (99.6 %) were enrolled in population studies
^bAmong patients included in studies on TTH only, 1,221 (8.7 %) had episodic TTH, 570 (4.0 %) had chronic TTH, and 12,309 (87.9 %) had TTH not otherwise specified. In total, 81 (0.6 %) were enrolled in clinical studies and 14,019 (99.4 %) were enrolled in population studies
^cAmong patients included in studies on CH only, 455 (76.6 %) had episodic CH, and 133 (22.4 %) had chronic CH, 6 (1.0 %) had other TACs. All patients were enrolled in clinical studies
^dAmong patients included in studies on mixed headache disorders, 137,118 (18.9 %) had migraine, of whom 132,167 had episodic migraine; 568,986 (78.6 %) had TTH, of whom 568,110 had episodic TTH; 24 (< 0.1 %) had CH or other TACs, of whom 13 had episodic CH; 18,044 (24.9 %) had other primary headache, of whom 339 were patients with both migraine-like and TTH-like headaches and 1667 had chronic daily headache not better specified, 2,337 had other primary headache not better specified and 12,571 had other non-migraine primary headache

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