Table 2.

Systematic Review Results From Table 1, Grouped by Categories^a

Characteristic	No. of studies	Family history rate of cluster headache, median (range), %
All population studies	22	8.2 (0–22)
Studies
With diagnosis in the proband made exclusively by in-person interview	13	6.7 (0–22)
Performed at headache centersa	16	6.8 (2–22)
Limited to first-degree relatives	6	7.3 (5–22)
With interviewswith relatives instead of relying on proband information	6	8.8 (2.0–20.8)
With inclusion of second-degree and/or third-degree relatives	8	9.7 (2.3–20)
With >500 participants	5	10 (2–18)

^aStudies performed at headache centers.^{13,18,20–22,24,26,28–33,36–38}