BE Masel et al. Archives of Physical Medicine and Rehabilitation. November (2001) Vol. 82 #11. p 1526.
A study of daytime sleepiness among TBI cases after apparently full recovery.
Case series n = 71, 38 months after injury. Measured objectively in a live-in sleep laboratory.
47% hypersomnolance rate did not show up on self-report. That is, the hypersomnolant were unaware of their tendency to sleep during daytime.
It is generally held that motorists who fall asleep at the wheel would be aware that there was a risk in advance. This work suggests that former TBI cases (after 38 months) were unaware of their risk of daytime sleeping.