Sleep

Does chronic sleep deprivation affect cognition in shift workers?

Virginia Thornley, M.D.
Neurologist, Epileptologist
March 6, 2019
Introduction
What is the impact of sleep on cognition of shift workers?
 
Does circadian misalignment have impact on cognition?
Those with circadian misalignment such as night shift workers are most affected in terms of sustained attention, visual-motor performance and processing of information(1).
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One study sought to clarify the relationship of circadian cycle misalignment with cognition. It found that on the first night of shift work, attention is markedly impaired which improves after the same schedule is followed. This did not hold true for areas in visual-motor or cognitive throughput. Cognitive throughput means the summation of data going through a network.
Declarative memory is stable while attention was greatly impacted. This may be because memory is not impacted by areas where the sleep-wake cycle is important.
 
Mechanism

It is thought that there is increased GABAergic tone at night which could depress cognition. The natural circadian rhythm allows for maximum cognitive abilities during the daytime. . This is when we get our peak performance. The worse time for vulnerabilities in cognition occurred in the hours between 4-6am(1).
The neurobiology is thought that lack of sleep at night affects the conduction of nerves including the local potential field which affects neuronal activity. This results in reduced reaction time and speed for visual motor performance and tasks requiring sustained attention (2).
Reference
  1. Chellappa, S.L.,Morris, C., Scheer, F.A. Effects of circadian misalignment on cognition in chronic shift workers. Sci. Rep., 2019, 9:699. published online 2019 Jan 24. doi: 10.1038/s41598-018-36762-w
  2. Nir, Y., Andrillon, T., Marmelshtein, A., Suthana, N., Cirelli, C., Tononi, G., Fried, I. Selective neuronal lapses precede human cognitive lapses following sleep deprivation. Nat Med. 2017, Dec: 23(12)1474-1480
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parasomnia

What happens with night terrors?

Virginia Thornley, M.D.
Neurologist, Epileptologist
February 1, 2019
 
Introduction
Night terrors can be terrifying events. But happens exactly?
Sleep
There are 3 states of arousal: wakefulness, non-REM (rapid eye movement) and REM sleep.
Non-REM has 4 stages. Stages 1 and 2 are light sleep. Stage 1 is characterized by attenuation of the posterior dominant rhythm and vertex waves can occur centrally. Stage 2 sleep is characterized by the presence of sleep spindles which are seen symmetrically in the central regions. Stage 3 is the deeper stage also called slow wave sleep. Stage 3 has delta wave activity.
When do parasomnias occur?
Parasomnias or disorders of sleep usually occur when one transitions from non-REM slow wave sleep.  Night terror is a type of parasomnia. Night terrors are a disorder of the usual transition. The mechanism of this dysfunctional transition is not clear.
This is in contrast to nightmares which occur during REM when dreaming occurs.
One study found that when there are frequent arousals or complex behaviors in a  polysomnogram this might correlate with night terrors. It might be a potential marker for occurrence of disorders of arousal such as night terrors (1).
Neurologybuzz.com
Reference
  1.  Lopez, R., Shen, Y., Chenini, S., Rassu, A.L., Evangelista, E., Barateau, L., Jaussent, I., Dauvilliers, Y., Diagnostic criteria for disorders of arousal: a video polysomnographic assessment. Ann. Neurol. 2018, Feb; 83(2):341-351
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Epilepsy, migraine

Sleep Hygiene especially for Migraineurs and those with Epilepsy

By Virginia Thornley, M.D., Neurologist, Epileptologist
February 15, 2018

Introduction
Many neurological diseases are affected by lack of sleep most significantly migraine and epilepsy. A person performs suboptimally with lack of sleep with inattention and lack of coordination. In someone with a neurological condition, the symptoms become even more manifest. Weakness becomes more prominent, double vision may be more pronounced and difficulty speaking will become more prominent. Sleep plays a vital role in the restorative function of the body.

Stages of sleep, why adequate and continuous sleep is refreshing
Sleep is divided into 2 categories, Non-REM (rapid eye movement) sleep and REM sleep. During non-REM sleep, there are 4 stages. Stage 1 and 2 constitute drowsiness which transitions into light sleep. The electroencephalogram is a study that reflects brain activity. Stages 1 and 2 demonstrates sleep complexes including vertex waves then K complexes. Sleep spindles occur during stage 2 sleep. During stages 3 and 4 also known as slow-wave sleep, delta waves which are the slowest waves between 1-3 Hertz start to occur. Stage 4 shows delta waves of greater than 50% of the recording. People enter these stages of sleep and then subsequent REM sleep. REM sleep is where dreaming occurs.

One can go through a few cycles of these so that you wake up refreshed. Continue reading

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