My husband is a sufferer of sporadic migraines. He is a police officer and enjoys working the night shift. Unfortunately for him, this shift is also his downfall. If he has to switch his sleep pattern for any reason (a daytime training, a weekend trip or activity, working overtime) he can usually expect one to come on. To prevent them, we have had to plan well ahead for activities so that he may take extra time off to slowly adjust the sleep schedule. Otherwise he keeps the same sleep schedule year round, even on days off. Anytime he has to sharply change his schedule, I cringe and await the call which usually means its right to the ER for treatment.
His other known triggers are excessive amounts of cheese, over exertion in workouts, and strong fluorescent lights.