Consistent results across questionnaire and sleep diaries, and
across participants, suggest that even on a “good” night, the
amount of sleep during a sleepover is only 5 h from a maximum
opportunity of 8 h (10 p.m. to 6 a.m.). On a “bad” night, participants
report only 2e3 h of sleep. A review of laboratory studies involving
total and partial sleep loss tentatively concluded that “clinically
significant” performance impairment is observed when sleep is
restricted below 5e6h(Dawson and McCulloch, 2005). Research
has indicated that sleep restricted to levels experienced in the
current study is associated with deficits that accumulate across a
week. Further, even after recovery opportunities of 8 h for three
days (the approximate TIB of participants on non-shift nights in the
study), performance in the restricted groups did not go back to prestudy
levels (Belenky et al., 2003). This suggests a level of impairment
that is not extinguished during three recovery days. Due to
the sleep restriction associated with their work patterns, participants
in the study may accrue a sleep debt that results in impaired
performance and may not be completely resolved during days off.