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SLEEP AND HEALTH
Early reports documented that untreated OSAS can have long-term negative effects, such
as failure to thrive, cor pulmonale and mental retardation. These severe consequences are
less common now due to early diagnosis and treatment, but recent reports have focused
on other long-term effects mainly related to neurocognitive deficits, such as poor learning,
behavioural problems and ADHD (Marcus, 2001).
Gozal and Pope (2001) tried to determine the potential long-term impact of early childhood
snoring. Analysing questionnaires of 797 children in a low academic performance
group (LP) and 791 in a high academic performance (HP) group, they found that frequent
and loud snoring during early childhood was reported in 103 LP children (12.9%)
compared with 40 HP children (5.1%). Therefore, children with lower academic performance
in middle school are more likely to have snored during early childhood and to
require surgery for snoring compared with better performing schoolmates. These findings
suggest that children who experienced sleep-disordered breathing during a period
traditionally associated with major brain growth and substantial acquisition of cognitive
and intellectual capabilities may suffer from a partially irreversible compromise of their
a priori potential for academic achievement. Three major components that result from
the intermittent upper airway obstruction that occurs during sleep in children could theoretically
contribute to such neurocognitive deficits, namely episodic hypoxia, repeated
arousal leading to sleep fragmentation and sleep deprivation, and periodic or continuous
alveolar hypoventilation.
Schooling problems may underlie more extensive behavioural disturbances such as restlessness,
aggressive behaviour, EDS and poor neurocognitive test performances. Nearly
20–30% of children affected by OSAS or loud and frequent snoring show important
signs of behavioural problems such as inattention and hyperactivity. Problems similar to
symptoms of ADHD are linked to the presence of repeated sleep arousals, and intermittent
hypoxic events, inducing a lack of behavioural inhibition with negative implications
for working memory, motor control and self-regulation of motivation and affect.
In contrast with these data, Engle-Friedman et al. (2003) recently found a significant
improvement of functions, at least in mild to moderate OSAS, when measured several
months following an adenotonsillectomy, but they confirmed that their results could not
rule out the possibility, even after treatment, of partial irreversible damage to academic
function that may be detected only later in life. In addition, they stated that adults who
also had deficits of neurocognitive executive functions related to the prefrontal area
failed to improve significantly after treatment.
The negative long-term effects may be mediated by the irreversible alteration of the prefrontal
cortex (PFC) and be related to structural changes of the brain as a consequence
of both hypoxaemia and sleep fragmentation induced by OSAS or other pathologies
affecting sleep.
In a recent report concerning OSAS adults, Macey et al. (2002) demonstrated grey matter
loss in cerebral sites involved in motor regulation of the upper airway as well as in
areas contributing to cognitive function (frontal and parietal cortex, temporal lobe, anterior
cingulate, hippocampus and cerebellum). It can be argued that, in critical stages of
brain development (that is, in childhood), these effects can lead to even more severe consequences,
which could explain the negative long-term effects.
It is speculative to think that the remodelling of the brain could also be mediated by sleep
and, therefore, sleep fragmentation could affect the process of brain plasticity (that is, the
capacity of the brain to modify its structure and function over time). Recent studies show-
NIGHT NOISE GUIDELINES FOR EUROPE