Individual differences in sleep Flashcards
individual differences?
= factors which lead to variation in people
AGE - struggle initiating and maintaining sleep when older
GENDER - not much research
- hormonal changes eg. menstrual cycle
- pre-menopause = women appear to need more sleep (need same as men post-menopause)
CIRCADIAN RHYTHM - biological clock - linked to chronotype
GENETICS
there are overlaps, so don’t look at them in isolation
The components of sleep regulation
1) circadian clock located in the SCN tells us when its appropriate to go to sleep and when to wake up
- daily rhythms involve:
1) sleep
2) body temp (drops in by 1c in evening to fall asleep and increases by 1 degree in morning)
3) hormone secretion
2) sleep homeostasis = the longer you’ve been awake the more you need sleep
ALSO, pineal gland which produces melatonin (biological representation of dark) =secreted at night
–> also helps regulate body temp
(all work v closely together = v vulnerable to disruption)
Sleep across the lifespan
sleep latency def
wake after sleep onset
REM
SWS
Stage 1 +2
percentage of the time spent in each stage
sleep latency = time it takes to get to sleep –> not much difference, but takes infants slightly longer = could be due to environment etc
we also sleep onset latency increase slightly again in late adulthood and old age
WASO = wake after sleep onset
-children between 5 and 10 sleep through the night
- 45+ = no. of times you wake up increases (weak bladder/ medical problems)
REM
- 0-5 yr olds spend a lot more time in REM
- not much difference between infants
SWS
- decreases as you get older
-needed more when younger potentially due to development
- changes in brain structure means we struggle to initiate and maintain deep sleep when we’re older (less neurons)
(could be linked to WASO –> not in deep sleep = more likely to wake up)
stage 1 + 2
not much difference between all age groups
Sleep in newborns
newborns haven’t developed a regular circadian cycle (due to brain and visual system still developing)
- sleep easily during the day and night
- don’t respond to environmental cues (need light to reset cycles, but they don’t have this)
- 16-18hrs per day
- each episode usually 2 cycles (discontinuous sleep –> 2.5 -4 hours as they get hungry)
- start cycles through REM
- more time in SWS (esp. stage 3)
- more REM
- shorter cycles of around 50-60mins
Sleep in the first year
circadian rhythm arises around 2-3 months (start responding to environmental cues)
- longer periods of sleep at night
- sleep cycles more regular
- sleep onset begins with NREM (go into stage 1 now)
- spend a lot of time in SWS (developing still)
- still more REM than adults
- cycle : 50-60 mins
- 6 months: sleep time reduces slightly and continuous sleep lengthens to around 6 hrs
- 12 months: 14-15hrs sleep with most being at night with 1 or 2 naps a day
Sleep in young children (1-5)
sleep decreases as age increases due to physiological social changes (nursery/ school)
- REM decreases
- longer cycles
= more typical of adult
- consolidated sleep at night (some naps still)
- 3-5 yrs discontinue napping ( Jenni & Carskadon, 2000)
Daytime vs nightime sleep
young children sleep a lot during day and night
get older = day time sleep decreases
Teenagers
effect on performance?
a lot of changes in sleep patterns and behaviours (due to biological clock)
- require 9-10hrs of sleep a night (Carskadon, 2003)
- due to changes during puberty
- delayed circadian rhythm due to changes in hormones (= sleep deprived lots due to school times) (delayed body clock) = go to bed much later in the evening (Waterhouse et al, 2012)
- homeostatic drive for sleep too low in teens in early evening = can’t counteract circadian rhythm
Kelley et al, 2015
- tested students at 10am and 2pm
- 13-14 yr olds
found: performed better in word pairs test later on (better in afternoon) - -> implications for later starting time at schools
Ideal sleep-wake cycle
other factors
- get up around the same time every day
- sleep around the same time every night
Other factors:
- social life = stay up late
- blue light from screens blocks melatonin = delays melatonin release
sleep in adults
- elderly tend to have: delayed sleep onset increased WASO/ fragmented sleep early-morning awakening decreased sleep stages 3 + 4 shorter REM (decrease REM and SWS could explain memory problems) frequent and shorter cycles
melatonin levels
young vs adults - differences in levels?
- younger children show higher concentration of melatonin
- older adults show very low levels of melatonin which could explain why they can’t maintain sleep during the night and often wake up
- low melatonin in day, 10 oclock = increase melatonin
- 5-10 yr olds have much larger increase than adults
- concentration drops as we get older (explains problems initiating and maintaining sleep)
Chronotype preference
ages
gender differences?
chronotype changes with age defo evening = 16-30 moderate evening = 31-41 intermediate = 42-58 moderate morning = 59-69 defo morning = 70-86 (teens = evening/ older adults = morning) -- genetic basis to chronotype -- gender differences? - men tend to go to bed later than women, but as we get older it tends to be around the same time
CLOCK genes
how many?
how do they work?
Period3?
% heritability?
chronotypes genetic basis
- approximately 18 CLOCK genes identified as being critically important for this internal rhythm
- they operate on a molecular feedback loop
- genes are turned on and produce a message which produces clock proteins
- these clock proteins work together, go into the nucleus + turn off their own genes = no more message = no more protein, protein degraded and then the whole thing repeats
so, there is a cycle of protein production and degradation
= this cycle provides the drive for circadian rhythm
one of the clock genes is Period3 - 2 forms:
1) homozygous PER3 5/5 = morning type
2) homozygous PER3 4/5 = evening type
morning/ eveningness estimated to be 50% heritable
morning types have shown increased slow wave activity at start of the night and also show greater deficits resulting from sleep deprivation
Morningness/ Eveningness
how do these types differ endogenously in the circadian phase of their biological clocks?
chronotype is linked to other biological processes that run on a 24hr cycle (circadian rhythm) - morning and evening types differ endogenously in the circadian phase of their biological clocks Morning type: - temp decreases around 10pm - increases in early hours of the morning (6am ish) = in line with sleep wake cycle - alertness peaks in the morning Evening type: - body temp decreases later - increases later in morning (8/9am ish) - alertness peaks in the evening (Kerkhof & Dongen, 1996)
-
effects of sleep deprivation on morning and evening types (Mane et al, 2014)
- 2 measures used?
- findings?
2 measures used:
- how easily they fall asleep unintentionally
- melatonin conc
found:
- morning have higher unintentional sleep than evening (overlaps with melatonin levels) (higher melatonin levels when falling asleep)
- sig difference in unintentional sleep episodes
dramatic increase in naps for morning types
(melatonin levels peak = unintentional sleep)
melatonin does increase for evening types too, but doesn’t result in naps as much
= morning types suffer more
