quantitative modelling of sleep-wake cycles and application to shiftwork svetlana postnova alertness...
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Quantitative modelling of sleep-wake cycles and application to shiftwork
Svetlana Postnova
Alertness CRC Ltd&
School of Physics, The University of Sydney, Australia
Alumni of the Physics Faculty at the Saratov State University, year 2004
Why model sleep-wake cycles?
• We spend 1/3 of our lives asleep
• Still don’t know why we need to sleep
• Lack of sleep leads to fatigue, accidents, stress, and disease
• 20% of fatal road accidents happen due to driver’s fatigue.
Picture from http://www.sdt.com.au/safedrive-directory-DRIVERFATIGUE.htm
Picture from http://www.coxsoft-art.com/6-methods-to-get-rid-of-fatigue/
Significant risk group - shiftworkers• work irregular hours sleep is disturbed• every 5th person works shifts, e.g. medical
personnel, police force, pilots, …• Poor quality of life• have twice the number of accidents• increased risk of disease, e.g., diabetes,
obesity, heart disease, and cancer.
Why model sleep-wake cycles?
Modelling can help to understand the biological system predict dynamics develop interventions
Photo from http://imannailah.blogspot.com.au/
Biology of sleep-wake cyclesSleep-wake cycles result from interaction between circadian and homeostatic processes
Homeostatic (H) –sleep need increases a function of time awakeCircadian (C)– oscillator with a ~24h period whose phase depends on light input
Borbely and Achermann, 1999, J Biol Rhythms
These processes affect the dynamics of sleep- and wake-active neuronal populations
Saper et al., 2005, Nature
H
C
Quantitative model of sleep-wake cycles
Based on biology
Simulates mean activity of neuronal populations involved in sleep-wake regulation (Neural Field Theory)
Validated against experiments
For full system of equations and detail seePostnova et al., 2013 PLoS one (open access)Postnova et al., 2012, 2014 J Biol Rhythms
For sleep-wake part of the model seePhillips et al., 2007 J Biol RhythsFulcher et al., 2010 J Theor Biol
Postnova et al., 2012, J Biol Rhythms
Quantitative model of sleep-wake cycles: how it works
Sleep Drive, D (mV)
VMA,
(mV)
Fulcher et al., 2010, J Theor Biol
wake
sleepCircadian phase is affected by light input:Light in the morning – advanceLight in the evening – delay
Light input depends on what you do, e.g.Go outside into sunlightStay up late with lights on
Circadian (C)
Homeostatic (H)
Sleep drive (D)
Fulcher et al., 2010, J Theor Biol
wake
sleep
wake
wake
sleep
sleep
Application to shiftwork: effects of shift light intensity
Postnova et al., 2013, PLoS one
Shift – awake
Break – sleep
Light intensity
* Circadian phase marker
room light bright light• Bright light improves adaptation to night
shifts• Amount of sleep increases in bright light
case
Slee
p dr
ive,
D (m
V)
before
after
room light bright light
after
before
• Sleepiness during shifts is significantly reduced in bright light case
Summary
• Quantitative biology-based modelling is a powerful tool that can improve understanding of the system and be applied to real-life problems
• The model of sleep-wake cycles was validated against experiments and also used to study - sleep of different animals, including dolphins and wales- effects of caffeine- effects of alarm clock set at different volume and time- effects of sleep deprivation- adaptation to jetlag- dynamics on different types of shift schedules
For references see http://sydney.edu.au/science/physics/research/complex-systems/brain-dynamics/index.shtml or google “brain dynamics complex systems USYD”
Write to spostnova@sydney.edu.au for questions
Acknowledgements
Prof. Peter Robinson (University of Sydney, Australia)Dr Andrew Philips (Harvard University, USA)Dr Ben Fulcher (Monash University, Australia)Dmitry Postnov (University of Copenhagen, Denmark)Romesh Abeysuriya (University of Sydney, Australia)Andrew Layden (University of Sydney, Australia)
And many other people who worked on the model
Funded by Australian Research Council and National Health and Medical Research Council through the Centre for Integrated Research and Understanding of Sleep (CIRUS)
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