Abstract
Daytime tiredness or sleepiness and deficits in cognitive performance
are common complaints in sleep disordered patients. Till now there
are few studies comparing patients from different diagnostic groups
of sleep disorders in the same experimental protocol. We studied
the time course of cognitive functions and subjective alertness in
a parallel group design with four groups of patients narcolepsy,
untreated or treated obstructive sleep apnea (OSA), or psychophysiological
insomnia and a control group of subjects without sleep complaints.
Each group consisted of 10 subjects, matched for age and gender.
After a night with polysomnography, subjects were studied for 10 h
from 08:00 hours to 18:00 hours at 20 min intervals under standardized
environmental conditions. Four psychological tests were applied,
(1) a critical flicker fusion (CFF) test to measure optical fusion
threshold (alertness); (2) a paper-and-pencil visual line tracking
test (selective attention); (3) a visual analog scale (VAS) for tiredness/sleepiness;
and (4) the Tiredness Symptoms Scale (TSS), a 14 items check list.
Each test session lasted for 8 min, followed by a 12 min pause. The
level and time course of cognitive performance and self-rating data
were analysed with hierarchical linear mixed effects models. Cognitive
tests showed decrements in alertness and selective attention in untreated
patients with insomnia, narcolepsy, and sleep apnea. Narcoleptic
patients and untreated OSA had a lower CFF threshold than controls,
and for narcoleptic patients the time course differed from that of
all other groups. In the visual tracking test the performance of
all groups of patients was worse compared with normal controls. Self-rated
tiredness/sleepiness was significantly more pronounced in the three
groups of untreated patients than in control subjects.
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