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SLEEP AND HEALTH 27
A recent study using actigraphy in normal school-age children showed that lower
sleep efficiency and longer sleep latency were associated with a higher percentage of
incorrect responses in working memory tasks; shorter sleep duration was associated
with performing tasks at the highest load level only. Also, controlling for age, gender,
and socioeconomic status, sleep efficiency and latency were significantly associated
with the mean incorrect response rate in auditory working memory tasks. This
study showed that sleep quality (evaluated as sleep efficiency = 100* [sleep + light
sleep]/duration) is more strongly associated with performance in working memory
tasks than sleep duration, suggesting that in assessing sleep, attention should be
directed not only at the amount of sleep but also at sleep quality.
2.3.1.5 Intelligence
Inspection of the mean IQ scores reported in the study by Rhodes et al. (1995) suggested
that their sample of five obese children with moderate to severe OSAS performed
in the borderline range whereas controls performed in the normal range.
Blunden et al. (2000) showed smaller deficits in children with mild SROBD whose
mean verbal and global IQ were in the lower end of the normal range.
It remains unclear as to whether the putative negative effects of SROBD on intelligence
are global in nature or confined to specific areas such as verbal rather than
performance or visuospatial intelligence and whether these impairments can be
reversed.
2.3.1.6 Learning and school performance
It has been widely reported (Stradling et al., 1990; Guilleminault et al., 1996;
Richards and Ferdman, 2000) that children with SROBD show reduced academic
performance and learning.
Weissbluth et al. (1983) found that poor academic achievers had a higher prevalence
of night-time snoring (38% vs. 21%) and breathing difficulties (13% vs. 6%). Out
of 297 children with SROBD (22% snorers and 18% sleep-associated gas exchange
abnormalities), 40% were in the lowest 10th percentile of academic performance
(Gozal, 1998) and SROBD in early childhood may continue to adversely affect learning
in later years (Gozal and Pope, 2001). Gozal (1998) found in his sample of poor
academic achievers that school grades improved post-adenotonsillectomy in treated
but not untreated children.
As well as those with SROBD, healthy normal children with fragmented sleep (measured
by actigraphy) also showed lower performance on neurobehavioural functioning
(NBF) measures, particularly those associated with more complex tasks, and also
had higher rates of behavioural problems (Sadeh, Gruber and Raviv, 2002).
Furthermore, in normal children without sleep disorders, modest sleep restriction
can also affect children’s NBF. Sadeh, Gruber and Raviv (2003) monitored 77 children
for 5 nights with activity monitors. On the third evening, the children were
asked to extend or restrict their sleep by an hour on the following three nights. Their
NBF was reassessed on the sixth day following the experimental sleep manipulation
and showed that sleep restriction led to improved sleep quality and to reduced
reported alertness.
These studies suggest that fragmented sleep or insufficient sleep is highly relevant
during childhood and that children are sensitive to modest alterations in their natural
sleep duration.
NIGHT NOISE GUIDELINES FOR EUROPE