|
In the further
pursuit of evidence, Dr. Bonnet's team decided to see whether
worsening sleep loss in people with psychophysiologic insomnia
would intensify previously observed insomnia correlates. The subjects
came to the laboratory for 10 nights. From two baseline nights,
the usual nightly sleep duration was determined and a calculation
of 80% of baseline determined and divided by four. On the next
seven nights, subjects were awakened to prevent sleep duration
from exceeding 80% of the usual amount in each quarter of the
night.
Bonnet and
his colleagues found that: 1) these insomnia subjects displayed
no significant change in subjective anxiety/tension (POMS) or
body temperature, and 2) they had decreased (as opposed to increased)
whole metabolic rate following nights of particularly poor sleep.
Subjects showed reduced MSLT values, indicating more sleepiness.
It was concluded that the features of primary insomnia displayed
by these subjects were not exaggerated by worsened sleep loss
and, therefore, are probably not related to sleep loss per se.
Besides mimicking
a psychophysiological-type insomnia sleep pattern, Bonnet and
colleagues have also mimicked an exaggerated stress arousal/activation
pattern in people with no sleep problems using doses of caffeine
as a stimulant. They saw support for the hypothesis that excess
stress arousal/activation is the source of the selected features
of insomnia. The features across conditions are compared in the
following chart (Bonnet
et al., 1996).
| Table
3.8.1: Dr. Bonnet's Studies
|
|---|
| Features
|
Yoked Control - Derived Insomnia
| Primary
Insomnia - psychophysiological-type
| Stimulant-induced
Hyperaroused/
Activated
|
|---|
Tension/anxiety
(POMS)
|
Decreased
|
Increased
|
Increased
|
|---|
Vigor
(POMS)
|
Decreased
|
Decreased
|
Decreased
|
|---|
Sleepiness
(MSLT)
|
Increased
|
Equal
or Decreased
|
Equal
or Decreased
|
|---|
Metabolic
Rate
|
Increased
(PM) Decreased (AM)
|
Increased
|
Increased
|
|---|
| Body
Temperature
|
Decreased
|
Increased
|
Increased
|
|---|
|
These
comparative data were used to support the contention that secondary
symptoms in patients with insomnia, and perhaps the poor sleep
pattern itself, occur through central nervous system hyperarousal
and not to sleep loss per se.
The
relationship of the symptoms of fatigue and tiredness to insomnia
or poor sleep raises the issue of distinguishing between sources
of fatigue. Insomnia is a concurrent symptom in many disease/illness
conditions, particularly those involving pain and fatigue. Tiredness
or sleepiness (often referred to as fatigue) attributable to sleep
disruption or loss is reported by large numbers of people in their
everyday lives. Fatigue in this context is related to the tendency
to fall asleep and the effort needed to resist it. This form of
tiredness should be distinguished from the hallmark symptom of
fatigue concurrent with many rheumatic, autoimmune, and mysterious
conditions such as chronic fatigue syndrome and fibromyalgia.
In these conditions, fatigue is expressed as a profound lack of
energy or exhaustion, fatigability upon exertion and not sleepiness.
Almost ubiquitously, disturbed sleep or reports of 'unrefreshing'
sleep is evident in such conditions. In many situations, it can
be unclear as to whether fatigue is primary in contributing to
sleep disturbance or whether sleep disturbance is primary in contributing
to fatigue or tiredness.
|