In the process of aging the sleep – wake cycle
changes, which can contribute to sleep problems. In a large-scale
survey in the United States involving people ≥55 years, 46-50%
reported one or more symptoms of insomnia. In older people with
intellectual disabilities (ID), besides the process of aging, their
neurological pathology may also contribute to issues involving a
good night’s rest. Several studies investigated sleep problems and
its consequences in children and adults with ID, resulting in
prevalence numbers varying from 13 to 86%. This wide range depends
on the subjects’ ages, used measures and definitions of sleep
disorders. Unfortunately, the particular prevalence of sleep
problems in older people with ID still remains unknown. Studies show
that in people with ID, sleep problems were positively associated
with irritability, stereotypy, hyperactivity, and possible
self-injurious behavior.
In addition, measuring sleep and sleep
problems in older people with ID admitted to day care centres poses
a number of challenges. Self-report on sleep characteristics is
prone to recall bias and as such often incomplete and unreliable,
especially in people with ID. Intermittent night-time visual
inspection is laborious, and also results in incomplete sleep data.
Polysomnography (PSG)—the gold standard is very accurate, but had
limited feasibility, because it requires expensive equipment and
expertise.
An alternative to PSG is actigraphy, which is
more and more used in sleep research. An actigraph is a small
device, often worn on the wrist that continuously measures motor
activity. From the data generated by the actigraph sleep and
wakefulness patterns can be derived. Studies show that actigraphy
has an agreement rate of 77% compared to PSG regarding sleep, but is
less capable of detecting wakefulness. In contrast, actigraphy is
non-invasive, does not disturb normal sleep and can be used in every
setting.