Time from onset until termination of an attack of headache (or pain), that meets criteria for a particular headache type or subtype. After a migraine or cluster headache attack, a low-grade non-pulsating headache without accompanying symptoms may persist, but this is not part of the attack and is not included when determining duration. If the patient falls asleep during an attack and wakes up pain-free, the time asleep is included in the calculation. If an attack of migraine is successfully arrested by medication but symptoms recur within 48 hours, this may either represent a relapse of the same attack or a new attack. Judgement is required to make the distinction (also see attack frequency).