4 individual differences in sleep

Question 1

The changes in sleep wake behaviour across the lifespan

Answer 1

sleep patterns change throughout the lifespan, with a significant decrease in SWS.
Developmental stages.
Can be explained by changes in the components of sleep regulation

Question 2

The differences between morningness - eveningness

Answer 2

Has a genetic basis

• Per3 5/5 - morning
• Per3 4/4 - evening

Question 3

the changes in the components of sleep regulation due to individual differences (age/ chronotype)

Answer 3

Morning types more vulnerable to affects of sleep deprivation.

Question 4

WASO, REM and SWS across the lifespan

Answer 4

Carskadon and Rechtschaffen (2005)

WASO-Wake after sleep onset amount of time spent awake after initially falling asleep
REM- children younger than 5 (0-5) spend a lot more time in REM sleep- not shown here.
SWS- decreases as you get older

Question 5

sleep in newborns

Answer 5

Newborns haven’t yet developed a regular circadian cycle- no regular rhythm.
They can sleep easily during the day and night. At this stage they don’t respond to environmental cues. We respond to light which helps us set our sleep-wake cycles.
Newborns sleep between 16-18 hours per day.
Each episode usually consists of 2 cycles.
Start their cycles through REM
Spend more time in SWS
Spend more time in REM sleep
Shorter cycles-Each cycle is approximately 50-60 minutes.
This is often discontinuous with each sleep episode lasting between 2.5-4 hours.

Question 6

sleep in the first year

Answer 6

Circadian rhythms begin to arise around 2 to 3 months of age. Start responding to environmental cues.
Leading to longer periods of sleep in the night and greater periods of wakefulness during the day.
Sleep cycles also change, becoming more regular.
Sleep onset now begins with NREM and REM sleep.
Spend a lot of time in SWS.
Each cycle is approximately 50-60 minutes.
By 6 months of age total sleep time reduces slightly and continuous sleep lengthens to approximately 6 hours.
By 12 months, the infant typically sleeps between 14 to 15 hours with the majority of sleep consolidated in the evening with one or two naps during the day.

Question 7

sleep in young children

Answer 7

Age 1-5
Amount of sleep decreases as the child gets older.
Both physiological factors as well as social factors influence this change.
REM sleep decreases
Longer cycles
Although they nap during the day they have consolidated sleep throughout the night.
Discontinue napping between the age of 3-5 years (Jenni & Carskadon, 2000).
Social Factors- attending school, regular routine. Where they sleep and with who.

Question 8

Children daytime vs. nightime sleep

Answer 8

Ferber and Kryger (1995)- Young children sleep quite a lot during the night and day.
As they get older their day time sleep decreases (is phased out) and the spend more time asleep during the night.

Question 9

Teenagers

Answer 9

Teenagers are really interesting. A complex relationship exists in adolescents. Show a lot of changes in sleep patterns and sleep behaviour- this is down to their biological clock.
Studies show that adolescents require 9-10 hours of sleep each night (Carskadon et al., 2003).

Delayed circadian clock.

Question 10

teenagers and performance

Answer 10

Kelley et al (2015)
The tested students at 10.00 in the morning and at 2pm to see whether the time of day influence how well they performed.
Students aged 13–14 were given a word pairs test at 10:00 and 14:00, and performed better when tested later.
Results show that the students performed better in the afternoon test in comparison to when they were assessed in the morning.

• , the homeostatic drive for sleepiness is usually too low to fully counteract the circadian drive for alertness, resulting in several hours where it is very difficult to fall asleep. In adolescence the timing of the circadian clock shifts later.

Question 11

sleep in adults

Answer 11

Neubaurer (1999) - . Compared with young adults, the elderly tend to have delayed sleep onset, fragmented sleep, early-morning awakening and decreased time in sleep stages 3 and 4. (REM = rapid eye movement).

Question 12

melatonin levels across ages

Answer 12

Karasek & Winczyk (2006)

Melatonin is important for sleep. Young children show a higher concentration of melatonin in comparison to adults.
Older adults show very low levels of melatonin which could explain why they cannot maintain their sleep during the night and often wake up.

Question 13

Chronotype

Answer 13

Chronotype changes with age.
Teenagers- more likely to be evening types
Older adults- more likely to be morning types.

Low scores indicate evening

Question 14

Chronotype

Answer 14

Chronotype changes with age.
Teenagers- more likely to be evening types
Older adults- more likely to be morning types.

Low scores indicate evening higher = morning

Question 15

Chronotype

Answer 15

Chronotype changes with age.
Teenagers- more likely to be evening types
Older adults- more likely to be morning types.

Low scores indicate evening higher = morning
(Roenneberg et al 2007)

• Normal distribution across the general population.

Question 16

Ronneberg et al 2007 - chronotype preference

Answer 16

Chronotype changes as we age. Young people are more likely to be evening types and older people are more likely to be morning types.
They also looked at differences between males and females. Men tend to go to bed later in comparison to women but as we get older men and women tend to go to bed around the same time.
Matching chornotype to work demands can be very useful.
Please note that they have used a slightly different questionnaire for this study to identify chronotypes- therefore higher scores indicate evening type, lower scores indicate morning type.

This chronotype preference has a genetic basis.

CLOCK genes.

Question 17

Clock genes : mechanism

Answer 17

Approximately 18 clock genes have been identified as been critically important for this internal rhythm.
They operate on a molecular feedback loop.
What happens is that these genes are turned on and they produce a message which produces a whole bunch of clock proteins.
These clock proteins then work together, go into the nucleus and actually turn off their own genes.
So no more message, no more protein, these proteins are then degraded and then the whole thing starts again.
So what you’ve got is essentially a cycle of protein production and degradation and it’s that cycle that gives the signal that drives the circadian rhythms.

Question 18

Type of clock genes

Answer 18

One of the CLOCK genes is period3
Homozygous PER 5/5 = morning type
Homozygous PER 4/4 = evening type.

Morningness–eveningness is estimated to be about 50% heritable.

Morning types have shown increased slow wave activity at start of the night and are also show greater deficits resulting from sleep deprivation.

Question 19

How does chronotype preference affect circadian rhythm

Answer 19

Kerkhof & Dongen (1996)

Chronotype is linked to other biological processes that run on a 24 hour cycle (circadian rhythm)
Morning- and evening-type individuals differ endogenously in the circadian phase of their biological clocks.
Morning type- temperature starts to decrease around 10pm. In the early hours of the morning it starts to increase again. This is in line with the timings of their sleep wake cycle.
Evening type- body temperature decreases later than the morning type, and it doesn’t goes back up until much later than the morning type.

Alertness
Comparison of subjective alertness between morning type and evening type.
Morning type- alertness is quite high in the morning, as they go through the day this alertness decreases.
It drops right down around 10pm which is they time for sleeping and in line with the body temperature drop.
Evening type- their alertness is quite low during the day and it peaks late in the evening.

Question 20

Morningness and eveningness effects of SD

Answer 20

Maire et al., (2014)
2 of the measures used were:
B. How easily they fall asleep unintentionally
D. Melatonin concentration

Morning types- have higher unintentional sleep episodes than evening types.
This overlaps with their melatonin levels. So at the time that morning types show higher levels of melatonin that the time they are more likely to fall asleep unintentionally.

Question 21

why might some poeple need more sleep?

Answer 21

Linked to sleep homoestasis.
During the day this sleep pressure builds up due to accumulation of adenosine.
Our brain is very active during the day and uses up ATP. That’s it’s driver i.e. the energy needed for the brain to perform its functions.
ATP is broken down during metabolism and converted into adenosine, so adenosine is a measure of metabolic activity.
As the day goes on and we use more ATP this leads to a build up of Adenosine and it seems that adenosine builds up in the prefrontal cortex which increases the sleep pressure and the drive to sleep.
So sleep duration are related to the response to the build up of adenosine in the brain. This is what researchers are proposing.