Saturday 2 December 2017
Warning: this post goes on a bit and may make you feel drowsy; if affected, make sure you are sitting comfortably...
We spend about a third
of our lives doing it. We would die without it. It is believed that all
mammals, birds, reptiles and fish, and many invertebrate animals do it.
Sleep is thought to be
essential for the well-being of any living creature with a brain. It is so
important that a number of species from blackbirds to dolphins are known to
alternate sleep on each side of the brain, so that they can keep an eye out for
predators at all times. This is called unihemispheric sleep.
Yet sleep is one of the
greatest mysteries in life: nobody knows why humans, or any other creatures,
need to sleep.
The biggest challenge
I currently have with Parkinson’s is the fatigue and this is closely related to
my sleep being very disturbed. Although I am typically in bed for nine hours
each night, I usually sleep for no more than three hours at a time and my
slumber is fragmented after the first sleep cycle.
I simply don’t get
enough good quality sleep and I’m knackered a lot of the time as a result.
Sleep problems are
very common in people with Parkinson’s and there appears to be no simple
solution. Medications, like a dose of melatonin, can help some people in the
short term but are not recommended for long term use.
So-called sleep
hygiene is often advised. This is stuff like building an association between
the bedroom and sleep (for example avoiding reading in bed) and getting into a
pre-bedtime routine. In my case, this misses the point. I have no problem
whatsoever getting to sleep; staying asleep is the issue, and I frequently lie
awake in bed for long spells between 3am and 6am. I guess this is simply
because the chemical balance in my brain is messed up, with either too much
dopamine or too little dopamine causing me to be too alert to stay asleep for long
periods.
But why do we even
need sleep in the first place?
I have my own ideas,
unsubstantiated and no doubt naïve, and they go like this…
The first thing to
understand is that there are two types of sleep: Rapid Eye Movement or “REM”
sleep and non-REM or “NREM” sleep. REM sleep is the sleep where we do most of
our dreaming and NREM sleep is deep sleep. They show completely different
patterns of brain activity and arguably are as distinct from each other as from
being awake. You can tell the difference when you are woken up suddenly. When awoken
from REM sleep you quickly adjust, but with NREM sleep you are groggy and
disorientated for a while.
The big clue for me is
that NREM sleep seems to be universal in pretty much all organisms with a
nervous system whereas REM sleep is confined mainly to birds and mammals. I think,
therefore, that NREM and REM sleep have very different purposes.
My preferred theory is
that NREM sleep is associated with the removal of neurotoxins built up from the
daily activity of nerve cells whereas REM sleep occurs when long term
memories are being formed.
To use an analogy with
a computer, NREM sleep is like switching the processor off for a while to let
it cool down, and REM sleep is a little bit like running a defragmentation tool
to tidy up storage on the machine when the disk space is getting full (on an
older PC; these days computers come with so much disk that they rarely need to
be defragmented).
In terms of the
neurotoxin removal, this is a well-established theory. It is thought that free
radicals (certain highly reactive chemicals) accumulate during normal neural
activity and these get cleared away during sleep when the neural activity is
suppressed. This is by no means the only viable theory in town. For example
there is the idea that sleep allows glycogen supplies (which fuel the neurons
in the brain) to build up again after being depleted when awake.
As for the memory
formation, the idea is that the brain needs to enter a special state for long
term memories to be hard-wired into neural connections; dreaming is a side
effect of watching all these memories being processed.
I often dream about recent events, all jumbled up. It's as if there is a sentient observer in the brain trying to make sense of a lot of random stimuli and stitching them together into a story. Using my computer analogy, it's like watching all the file names flash up on screen as the defragmentation tool scans through the disk and trying to interpret them into something meaningful, when in fact they are just a random replay of stuff stored on the machine.
There is quite a lot
of evidence that learning is impacted by the quantity of sleep and it is well
known that children and teenagers need more sleep than adults. Moreover, there is growing evidence that new memories
of events and facts first form in a central region of the brain called the
hippocampus and from there get transferred to the rest of the brain. In
Alzheimer’s disease, often the hippocampus is affected first, impacting
short-term memory and from there the disease spreads to the rest of the brain,
gradually degrading long term memories as well.
I have grossly
over-simplified matters and am probably incorrect in a number of areas. For example,
there are three stages of NREM sleep in humans, all with slightly different
characteristics. There are other types of memory like knowing how to ride a
bike: these “procedural” memories that control motor skills are in the domain
of the cerebellum. And there are other effects of sleep like letting the body
rest and repair itself.
The truth is that
nobody knows for sure why we all need to sleep, but I hope the essence of my
theory is not too far off the mark.
The regulation of
sleep is a whole other story, though somewhat better understood. It is linked
to the concept of circadian rhythms, following the clock of nature, so that we
sleep during the night when it is dark, and are stimulated to be awake by
natural daylight. There are various chemical messengers involved, like
melatonin, but, again, the jigsaw has yet to be fully assembled.
So, following my
argument through to its conclusion…
My natural sleep rhythms
are disrupted by my Parkinson’s due to the imbalance of dopamine in my brain;
which means I don’t get quite enough sleep; which causes me to be less alert
during the day (too many toxins) and struggle with memory (I sometimes forget
people’s names and recent conversations, perhaps because they haven’t
transferred effectively to my long-term memory).
My situation is not
the same as everyone else who has sleep problems with Parkinson’s, but it is
common enough.
I have asked a number of medical professionals including The Professor and the Parkinson's Nurse for advice but they haven't been able to offer anything useful.
In fact, the most effective
remedy I have found for my own issues is the afternoon power nap. Twenty or thirty minutes in la-la land during the early afternoon works wonders for both my mind
and my body. Afterwards I feel energised and mentally sharp again. If only there was somewhere to snooze in the office...
I suppose this is not
unlike men and women who sail around the world single-handed. Ellen Macarthur
slept for no more than twenty minutes at a time during her 71-day world record
solo circumnavigation of the world in 2005.
Maybe there’s another
clue here somewhere. If we could
understand why power naps are so effective, perhaps we could better understand
the nature of sleep itself.
