Sleep Health Science and Interventions Flashcards
How much sleep does the average US adult get a night?
6hrs 57mins
37% get <7hrs / night
What % of people get less that 6hrs sleep a night?
20%
List 2 indirect costs associated with insomnia
1) Presenteeism (people at work but not productive)
2) Long-term disability (increased risk)
Generally what is the nightly sleep requirement for most adults?
7-8hrs (no recognised objective test for how much sleep any one individual requires)
Definitions:
a) Circadian
b) endogenous circadian oscillators
c) Entrainment
a) “circa” = about “dia” = day
b) endogenous circadian oscillators = molecules, cells and tissues that comprise the body’s “internal clock”
c) entrainment = the ability to be brought into a rhythm
(synchronisation of internal endogenous oscillators based on external inputs)
Where are the body’s central oscillators found?
the Suprachiasmatic Nucleus (SCN) - the main “body clock”
Where is the SCN located in the brain?
Within the hypothalamus
Where are the body’s peripheral oscillators found?
Every major organ of the body and allow alignment between central and peripheral clocks
(kidneys, liver, heart, adrenal glands and pancreas)
Summarise what ‘circadian rhythms’ are
Biological processes that are regulated by central and peripheral oscillators that are capable of being brought into a rhythm (usually 24h) to help align physiological functions and behaviours with solar light-dark cycles
At what time of day do we experience a cortisol spike?
On awakening / early morning
What provokes the morning cortisol spike?
anticipation of food
(therefore to train the spike to come later, and wake later, can advise to eat breakfast / drink caffeine 45mins after desired waking time)
What is the name of the neuronal tract between the retina and the SCN?
The retinohypothalamc tract
used to entrain central oscillators via light-exposure
There is a neuronal tract between the SCN and what gland which controls melatonin secretion?
the Pineal Gland
(function not fully understood but involved in female reprod / sexual maturity as well as circadian rhythms re sleep / wake cycle -> melatonin)
Splanchnic nerves are part of what aspect of the nervous system?
Autonomic Nervous System -> innervate the adrenal glands
Adrenals glands help to regulate what 3 mechanisms via the hormones epinephrine, norepinephrine, glucocorticoids and aldosterone?
1) Blood flow
2) Temperature
3) Food intake
What are Retinal Ganglion Cells (RGCs)?
Non-visual light-sensitive retinal neurons
What is melanopsin
the photopigment in retina ganglion cells (RGCs)
What type of light is melanopsin maximally sensitive to?
short wavelengths -> blue light
Darkness has what effect on pineal secretion of melatonin?
Darkness triggers melatonin secretion from pineal gland
Melatonin secretion leads to what (vast) operators and outputs?
Cutaneous vasodilation -> peripheral warming -> Cooling of core body temp -> sleep initiation
List 4-5 physiologic changes that occur in EARLY sleep (first 1-4 hours of sleep)
1) Rise in melatonin
2) Slow wave on EEG predominates (restorative)
3) Decreasing core body temperature / increased peripheral
4) Decreased blood pressure and sympathetic tone
5) restorative processes throughout body
List 4 physiological processes that occur THROUGHOUT sleep
FAM
1) DNA remodelling and repair
2) Leptin secretion
3) Gradual increase in cortisol
4) Fatty acid metabolism
List 4 physiologic changes that occur in LATE sleep
1) Declining melatonin levels
2) Longer REM periods
3) Increasing BP, sympathetic tone and baroreceptor sensitivity (ability to change BP rapidly by altering HR, contractility and peripheral vascular tone)
4) Awakening -> cortisol spike
REM periods of sleep play an important role in what psychological process?
Fear extinguishing
What is the predominant entraining force of the SCN clock?
a) Light b) Food c) fluid status d) ambient temp
Light
In what units is light-intensity measured?
Lux
How many lux is bright ‘noon’ sunlight approximately?
100K lux
cloudy: 25K lux; Overcast 2K - 10K lux; full moon 1 lux
How many lux is household lighting approximately?
50-200 lux
(Bright industrial lighting: 1-5K lux
Kitchens & Offices 200-500 lux)
Light in nanometres (visibility) vs Kelvin (colour relative to temperature)
In nm what light range does blue light fall within?
At what temperature is blue seen?
Blue light spectrum: 420-480nm
Blue light dominant at: 6500 Kelvin
Is blue light or orange light dominant at higher temperatures?
Blue light is warmer
blue light: 6500 Kelvin
orange/red: 2500 Kelvin (approx)
What effect does blue light have on melatonin?
Blue light suppresses melatonin
What effects does blue light exposure have - list unto 7 effects?
increases x 4
decreases
suppresses
inhibits
BLUE LIGHT:
1) increases HR, BP, core body temp
2) Decreases sleepiness
3) suppresses melatonin
4) increases cortisol
5) increases sympathetic tone
6) increases altertness
7) inhibits sleep onset and shifts sleep cycle later
(OVERALL leads to delayed phase - like Westward travel)
List at least 3 frequently used items which expose us to blue light (and therefore should be avoided close to bed)
1) Back-lit computers
2) TV screens
3) phones
What impact does low daylight have on the body’s sensitivity of melatonin suppression?
Low daylight INCREASES the SENSITIVITY of MELATONIN SUPPRESSION in response to LIGHT at NIGHT
e.g. 6.5hrs of exposure to 10K lux of light on an overcast day CANNOT fully overcome nighttime melatonin suppression from exposure to 90 lux of light (within household lighting range)
Delayed phase shift i.e. delaying sleep onset can occur with Westward or Eastward travel?
Westward = delayed
Advanced phase shift i.e. early waking can occur with Westward or Eastward travel?
Eastward = advanced
Are ‘night owls’ or ‘morning larks’ more susceptible to melatonin suppression>?
Night owls
Few people have 24h circadian rhythms - do the majority have delayed phase shift or advanced phase shift?
Majority have delayed phase shift
Average SCN clock = 24hr and 8mins