Perhaps blood volume insufficiency is a major cause of migraine.

"The occurrence of migraine in women is influenced by hormonal changes throughout the lifecycle. A beneficial effect of pregnancy on migraine, mainly during the last 2 trimesters, has been observed in 55 to 90% of women who are pregnant", (1). Why do two thirds of pregnant migraineurs see an improvement in symptoms? I believe it may be due to the blood volume expansion. However, I have come across a paper that has me questioning the my previous beliefs on the mechanisms of benefits from blood volume expansion, (2). Nevertheless, benefits still clearly seems autonomic in nature, (3). Given that pregnancy doesn't improve sleep in any obvious fashion, the mechanism for migraine improvement appears independent of sleep.

I have been sick for a few days. Headache has been one of the primary symptoms. I experience headaches regularly regardless. I almost never experience tension headaches (or, rather, what feel like tension headaches). Interestingly, however, during my sick period my headaches were worse during orthostasis (standing). The throb was very dramatic; I could feel each heart beat precisely. My supine (lying down) heart rate was 100 bpm. I didn't measure my orthostatic heart rate. Orthostatic headaches were more persistent than supine ones. In fact, the majority of supine headaches lasted only a dozen or so heartbeats, and only initiated due to plopping down on the bed. Retrospectively, nearly all of my everyday headaches may be orthostatic. I would like to see a study on albumin infusion as an attempt to treat migraines. I would expect both sleep-dependent and sleep-independent improvements. I don't know why people so rarely look for/at upstream disease causes and treatment.

FYI, acetaminophen (tylenol) doesn't appear to impair sleep, while NSAIDs (aspirin, ibuprofen) do.

(1) Migraine in pregnancy:
https://www.ncbi.nlm.nih.gov/pubmed/9825951

(2) Drug-induced arterial pressure elevation is associated with arousal from NREM sleep in normal volunteers:
http://jap.physiology.org/content/87/3/897.long

(3) Migraine: A Chronic Sympathetic Nervous System Disorder:
http://www.medscape.com/viewarticle/466937_1