L15 - Optimum Sleep and Sleep Loss

Question 1

What are some forms of sleep impairment?

Answer 1

• Sleep Deprivation - complete absence of sleep
• Sleep Restriction - shortened sleep time
• Sleep Fragmentation - normal sleep times but poor quality sleep, for eg. frequent arousals

Sleep loss is inadequate sleep due to any of the above.

Question 2

What is the downside of studying sleep restriction or fragmentation?

Answer 2

It’s most costly, as it has to go over a greater amount of time to see effects.

Sleep deprivation is less common in society but much easier and cheaper to study.

Question 3

Contrast sleepiness and fatigue.

Answer 3

Sleepiness - reduced alertness due to increased PRESSURE TO SLEEP. Can result from circadian and sleep homeostasis factors.

Fatigue - decreased capacity to continue a task as a consequence of prolonged work.

Sleepiness can lead to fatigue.

Question 4

What is the average sleep?

Answer 4

• Around 7-8hours
• The average has decreased since 1985, could mean that we are chronically sleep deprived, or evolved.
• We have more stimulants than before, and more food readily available.

Question 5

What is evidence showing that the population may be chronically sleep deprived?

Answer 5

• People are sleeping 2-3 horus extra on weekends. Could be sleep rebound from sleep dep during the week

HOWEVER

could also be optional sleep although we don’t need it, but we can..

Question 6

What is the optimum sleep duration associated with morality?

Answer 6

• Lowest mortality rates seen when people sleep 7 hours a night
• shorter sleep durations increased mortality
• long sleep durations actually increased mortality

although, maybe people who slept longer had comorbid health issues

Question 7

In what ways can sleep loss impair performance?

Answer 7

• slower RT (only reduced by 35msec after 36 hours sleep dep) - small but can be critical when driving
• Reduced vigilance - performance on attention based tasks declined, mostly due to lapses of attention (milliseconds) –> tested on psychomotor vigilance task, where you must sustain attention for 10 mins, and recorded RT when target goes red. IF RT over 500ms, then it’s an attention lapse.
• Deficits in info processing - processing and integration takes longer, memory accuracy reduced.

Question 8

What was found when sleep restriction was tested over time

Answer 8

• Working memory, visual scanning, and a motor element all declined with sleep restritcion over 0-14 days
• there was some deterioration even in people who had to sleep 8 hours for PVT task
• evident that effects of sleep restriction does not have immediate effects, but over the long term it is bad.

Question 9

What happened when Van Dongen (2004) investigated individual traits in sleep deprivation?

Answer 9

• huge variability between subjects in performance after sleep dep
• Different tasks were affected differently by sleep
• People tended to report similar amounts of ‘sleepiness’ regardless of how much that person got –> trait factor
• the amount of sleepiness felt has little correspondence to actual performance
• some reported high levels of sleepiness but performed really well, and some reported low levels of sleepiness but seemed more affected by sleep dep

INDIVIDUAL DIFFERENCES ARE VERY IMPORTANT

Question 10

Link between sleep and cardiovasc health?

Answer 10

Risk is greatest (15% increased risk) when you report 6 or less hours of sleep per night, and poor sleep quality.

• adjusted for sex, age, lifestyle factors, subjective health and eduational level.

Question 11

What are metabolic associations with sleep?

Answer 11

Epidemiological studies show short sleep duration is associated with obesity and diabetes.

U-shaped curve - also increased risk with more sleep.

Also found that those who were sleep deprived ate more.

• hormonal changes
• 340 more calories consumed on ad lib day after 4.5 sleep condition (as opposed to 8.5 hr)
• the sig diff was found in SNACKS, particularly carbs

Question 12

What is the optimal sleep duration for physical health?

Answer 12

7-8 hours

due to cardiovascular risk and obesity findings

Question 13

How flexible is sleep duration, and how helpful is recovery sleep?

Answer 13

• found that after 5 days of 4hr sleep duration, most participants did not perform at baseline level on neurocog tasks after 10 hours recovery sleep
• AMOUNT of recovery sleep and AMOUNT OF SWS is also important.
• AMOUNT of iNITIAL SLEEP DEP
• the task being measured

some flexibility..