Fig. 1. Impact of headache as assessed using the HIT-6 among individuals with migraine in the 2009 Korean Headache Survey and the 2018 Korean Sleep-Headache Survey. HIT-6 scores: little to no impact, <50; some impact, 50–55; substantial impact, 56–59; severe impact, ≥60. HIT-6: Headache Impact Test-6.