Several epidemiological
studies have shown the presence of
comorbidity between various types
of sleep disorders and different
headache subtypes. Migraine without
aura is a sensitive risk factor for
disorders of initiating and maintaining
sleep (odds ratio (OR) 8.2500),
and chronic tension–type headache
for sleep breathing disorders (OR
15.231), but headache disorder is a
cumulative risk factor for disorders
of excessive somnolence (OR
15.061). This result has not been
reported in the clinical literature.