Parents of children with ADHD often report that their child has sleep
difficulties, even among children not treated with medication. In
fact, it is estimated that between 25% and 55% of parents whose child
has ADHD complain of sleep difficulties in their child.
Given these widespread concerns, sleep issues can be quite relevant to
the treatment of children with ADHD. Sleep difficulties can be a
significant source of distress for children and/or their parents and
sleep problems may worsen ADHD symptoms. For example, a child who
struggles with attention problems is likely to have even greater
difficulty focusing if he/she does not obtain the proper amount of
sleep.
Sleep studies in children with ADHD can provide either subjective or
objective information about sleep patterns. Subjective studies
typically rely on questionnaires completed by parents that inquire
about different aspects of children's sleep. Objective studies
employ laboratory measures to obtain precise estimates of different
sleep parameters including sleep onset latency, i.e., how long it
actually takes the child to fall asleep, sleep efficiency, i.e., the
ratio of time spent asleep (total sleep time) to the amount of time
spent in bed, sleep stage shifts, i.e., the number of shifts between
different stages of sleep, true sleep time, i.e., the amount of time
actually spent asleep, and sleep apnea/hypopnea, breathing difficulties
during sleep.
The authors of this study [Cortese et al., (2009). Sleep in children
with Attention-Deficit/Hyperactivity Disorder: Meta-analysis of
subjective and objective studies.
Journal
of the American Academic of Child and Adolescent Psychiatry, 48,
894-908.] began by identifying all studies published since 1987 that
compared sleep in children with ADHD versus controls. Only
studies that used DSM-IV diagnostic criteria to identify participants
with ADHD and that excluded children receiving medication treatment or
who may have had a mood or anxiety disorder - which can also compromise
sleep - were included in the analysis.
These inclusion criteria were applied to permit a comparison of sleep
in children with and without ADHD that was not contaminated by possible
medication effects or by other disorders. Because Oppositional
Defiant Disorder (ODD) co-occurs so frequently with ADHD, and most
available studies did not exclude children with ODD, studies that
included children with ADHD and ODD were included in the pool of
studies.
A total of 16 studies - including 6 providing subjective sleep data, 13
providing objective sleep data, and 6 providing both types - were
retained for analysis. The pooled sample size across these
studies was large: 722 children with ADHD and 638 controls. To
analyze ADHD vs. control differences, the authors used a statistical
technique called meta-analysis which combines results across different
studies. Combining data across studies allows for a larger sample
size and is generally believed to produce more stable and reliable
results than those derived from on a single study. Of course,
only studies that measure the same sleep parameters can be combined, so
none of the results reported below are based on the entire universe of
participants.
-
Results -
Subjective reports of parents - Children with ADHD were reported by
parents to show higher bedtime resistance, greater difficulty falling
asleep, more night awakenings, greater difficulty waking up in the
morning, and more sleep disordered breathing, e.g., snoring, compared
with controls. They were also described by parents as being more
sleepy and less alert during the day.
Objectively recorded sleep differences - Several objective measures of
sleep differences between children with ADHD and controls were also
found. Specifically, children with ADHD took more time to fall
asleep, had lower sleep efficiency (less time actually sleeping
relative to time spent in bed), displayed more stage shifts
(transitions from one sleep stage to the next), obtained less true
sleep time, and had greater instances of apnea/hypopnea. When
presented with opportunities to nap during daytime hours, they fell
asleep faster than controls, consistent with the idea that they are
more tired during the day. No differences were found in other
objectively measured parameters of sleep including time spent in stage
1 and stage 2 sleep, time spent in slow-wave sleep, night awakenings,
and REM sleep latency.
-
Summary and
Implications -
This is the first meta-analysis including data from subjective and
objective studies comparing sleep disturbances in nonmedicated children
with ADHD who were without mood or anxiety disorders to controls.
Results indicate that parents of children with ADHD perceive their
child to have greater difficulty on a number of sleep dimensions
compared to other parents.
Although parent ratings of sleep may reflect a 'negative halo effect' ,
i.e., the sleep ratings made by parents of children with ADHD are
negatively biased because of the difficulties their child has during
the day, the objective studies also indicate significant differences in
sleep quality among children with ADHD. Thus, an important
caution raised by the authors is that parents may sometimes view their
child's sleep difficulties "...as the expression of a general
oppositional attitude, thus ignoring the cause of the child's behavior,
which may be the expression of an underlying real sleep disturbance
that manifests itself with behavioral difficulties.
It is especially instructive to note those aspects of sleep where
parents' reports and objective data coincided. Thus, objective
measures of apnea/hypopnea were consistent with parents' reports of
greater sleep disordered breathing in children with ADHD.
Similarly, objective measures of shorter latency to fall asleep during
nap opportunities is consistent with parents' reports of children with
ADHD tending to be sleepier during the day. This is not
surprising given evidence in the objective measures of lower sleep
efficiency and less true sleep time in the children with ADHD.
Along these lines, it is surprising that although children with ADHD
tended to fall asleep faster at nap opportunities during the day, their
latency to fall asleep at night was longer.
Overall, the authors conclude that available evidence indicates that on
average, children with ADHD are more impaired in their sleep than other
children. As noted above, because medication-treated children and
children with mood or anxiety disorders were excluded from their
analysis, these differences are likely to be directly related to ADHD
itself. However, because children with ODD were not excluded, it
is possible that some of the differences observed are reflective of
significant oppositional behavior rather than ADHD per se, e.g.,
bedtime resistance.
Although this was the most thorough analysis of sleep difficulties in
children with ADHD conducted to date, the authors note that the strict
criteria used for study inclusion resulted in a relatively limited
number of studies being retained in their review. Therefore, they
do not feel that their results can be used to inform evidence-based
guidelines for the management of sleep disturbances in children with
ADHD. However, their work highlights that sleep difficulties in
children with ADHD are not uncommon, and such difficulties may
exacerbate a child's symptoms and further impair day-time
functioning. Parents of children with ADHD should thus be alert
to the possibility that sleep problems are contributing to their
child's difficulties, and should consult with their child's health care
provider should they have concerns about this.