Facts About Sleep: 12 Interesting Psychological Studies

12 facts about sleep that come from interesting psychology studies.

12 facts about sleep that come from interesting psychology studies.

It is a fact about sleep that it delivers beautiful rewards — if you can get enough of it.

Sleep has profound effects on our memories, desires, self-control, learning, relationships and more.

Here are twelve studies which demonstrate some facts about sleep, including its benefits and a few of the dangers of not getting enough.

1. Facts about placebo sleep

Sleep is slippery beast, not least in how it’s susceptible to our perceptions of its quality.

If we think we’ve had a wonderful sleep last night, we feel and perform better, even if our sleep was actually the same as usual.

This is what Draganich and Erdal (2014) found in a study which had participants hooked up to sensors which they were told were measuring the quality of their sleep.

Actually the sensors weren’t measuring anything. Instead the researchers randomly told some people they’d had better sleep than others.

When they were given a cognitive test the next day, those who’d been told they slept the best also did the best in the test.

Their self-reported sleep quality had little effect on the test results.

The researchers dubbed this ‘placebo sleep’.

2. Emotional sleep

During sleep our memories are reorganised and made stronger–in particular the emotional centres of the brain are highly active.

Psychologists have found that it is a fact about sleep that our mind is cataloguing our memories and deciding what to keep and what to throw away.

Sleep expert Elizabeth A. Kensinger explains:

“Sleep is making memories stronger. It also seems to be doing something which I think is so much more interesting, and that is reorganizing and restructuring memories.”

A review of studies on sleep found that we tend to hold on to the most emotional parts of our memories (Kensinger & Payne, 2010).

3. Full moon facts about sleep

If your sleep wasn’t up to scratch last night, perhaps it was partly down to the phase of the moon.

People often complain of worse sleep around the full moon, but until recently scientists have been sceptical.

A study by Cajochen et al., 2013, though…

“…studied 33 volunteers in two age groups in the lab while they slept. Their brain patterns were monitored while sleeping, along with eye movements and hormone secretions.”

This is what they found:

“The data show that around the full moon, brain activity related to deep sleep dropped by 30 percent. People also took five minutes longer to fall asleep, and they slept for twenty minutes less time overall.

The researchers think it may be because we have a kind of ‘moon clock’ inside us that tracks its cycles and affects our hormone levels.

This is in addition to the better known circadian rhythms which affect many bodily processes during the day.

→ Read on: Bad Night’s Sleep? Blame the Full Moon

4. Facts about sleep and food cravings

One of the dangers of not getting enough sleep is craving junk food.

Research from UC Berkeley scanned the brains of 24 participants after both a good and a bad night’s sleep (Greer et al., 2013).

After disturbed sleep, there was increased activity in the depths of the brain, areas which are generally associated with rewards and automatic behaviour.

It seems a lack of sleep robs people of their self-control and so their good intentions are quickly forgotten.

Hence those junk food cravings get out of control.

→ Read on: Why the Sleep-Deprived Crave Junk Food and Buy Higher Calorie Foods

5. Facts about learning in your sleep

It’s not possible to learn something new when you sleep, like a foreign language, but you can reinforce something you already know.

Gobel et al. (2012) found that students learned to play a series of musical notes better after listening to them during a 90-minute nap.

One of the authors, Paul Reber explained:

“The critical difference is that our research shows that memory is strengthened for something you’ve already learned. Rather than learning something new in your sleep, we’re talking about enhancing an existing memory by re-activating information recently acquired.”

→ Read on: Offline Learning: How The Mind Learns During Sleep

6. Benefits of a six-minute nap

Even tiny amounts of sleep can be beneficial.

A study by Lahl (2008) found that even a short six-minute nap was enough to measurably improve performance on a test of word recall.

Tell that to the boss the next time your caught ‘resting your eyes’ at work!

7. Night owls have lower integrity white matter

Different neural structures have been discovered between people who are night owls and early risers.

Research on 59 participants, those who were confirmed night owls (preferring late to bed and late to rise) had lower integrity of the white matter in various areas of the brain (Rosenberg et al., 2014).

Lower integrity in these areas has been linked to depression and cognitive instability.

Unfortunately work, school and other institutions mostly require early rising, which, for night owls, causes problems.

As night owls find it difficult to get to sleep early, they tend to carry large amounts of sleep debt.

In other words, they’re exhausted all the time and their brains clearly show the consequences.

→ Read on: Like to Stay Up Late? Different Neural Structures Found in the Brains of Night Owls

8. Facts about children’s sleep

Children are processing way more information than adults because everything is so new to them.

That is why irregular bedtimes at a young age can reduce their cognitive performance.

One study had children learning a task which had a hidden pattern. After a night’s sleep they were much more likely to guess the secret pattern without being told (Wilhelm et al., 2013).

Children also outperformed adults, suggesting that sleep was more important to them for this task.

9. Adolescents need more sleep

Adolescents typically require an hour or two more sleep than adults.

If so, why do we make them get up so early for school?

One study has delayed the waking up time of adolescents at a boarding school by just 25 minutes (Boergers et al., 2013).

They found that afterwards the number of students getting more than 8 hours sleep a night jumped from 18% to 44%.

On top of this, the students experienced less daytime sleepiness, were less depressed, and found themselves using less caffeine.

→ Read on: Later School Start Times Improve Sleep and Daytime Functioning in Adolescents

10. Consolidate motor skills

When we are learning a motor skill, like playing the piano, our brains continue to process the information after we’ve finished.

In research by Allen (2012), musicians who practised a new song had improved in speed and accuracy compared with before a night’s sleep.

Like memory, a good night’s sleep can also improve motor performance.

11. Facts about relationship damage

People are usually at their worst after a bad night’s sleep, but what does that do to their intimate relationships?

A study finds that it is a fact about sleep that even one bad night’s sleep can be surprisingly damaging to a relationship (Gordon & Chen, 2013).

They found that even for those who were good sleepers, just a single night’s poor sleep was associated with increased relationship conflict the next day.

→ Read on: How Just One Night’s Poor Sleep Can Hurt a Relationship

12. Hidden caves open up during sleep

If sleep has such amazing restorative powers then what is going on physiologically?

Research has discovered “hidden caves” inside the brain, which open up during sleep, allowing cerebrospinal fluid (CSF) to flush out potential neurotoxins, like β-amyloid, which has been associated with Alzheimer’s disease (Xie et al., 2013).

The flushing out of toxins by the CSF may be central to sleep’s wondrous powers.

→ Read on: Hidden Caves in the Brain Open Up During Sleep to Wash Away Toxins

Last word

Last word to the playwright Wilson Mizner who said:

“The amount of sleep required by the average person is five minutes more.”

Quite right.

→ Related: 10 Sleep Deprivation Symptoms

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Sleep Is At The Heart Of Almost All Mental Health Issues (M)

Whether it is anxiety, schizophrenia, Tourette’s or depression, all have circadian rhythm disruption in common.

Whether it is anxiety, schizophrenia, Tourette's or depression, all have circadian rhythm disruption in common.


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The Strange Way Just 2 Hours Less Sleep Affects The Emotions

Lack of sleep affects all kinds of cognitive functions, including memory, attention and learning.

Lack of sleep affects all kinds of cognitive functions, including memory, attention and learning.

As little as two hours less sleep than normal is enough to change people’s emotional experience during the day, a study finds.

People feel fewer positive emotions after just one night of reduced sleep.

However, people did not feel more depressed after getting less sleep than normal.

So, people’s emotions change, explained Dr Ingvild Saksvik-Lehouillier, the study’s first author, but…

“…not in the sense that we have more negative feelings, like being down or depressed.

But participants in our study experienced a flattening of emotions when they slept less than normal.

They felt less joy, enthusiasm, attention and fulfilment.”

The study included 52 people who slept for two hours less than normal and then were given tests of their emotions.

Dr Saksvik-Lehouillier explained:

“In the imposed sleep deprivation phase, participants crawled under their covers two hours later than they normally did, and had to get up at their usual time.”

Lack of sleep affects all kinds of cognitive functions, including memory, attention and learning.

However, the researchers were most interested in its effects on the emotions, particularly as poor sleep is linked to mental health problems.

Dr Saksvik-Lehouillier said:

“We didn’t find clear differences when it came to the negative emotions, but there were marked differences for the positive ones.

Positive feelings scored worse after just one night of reduced sleep, and dropped even more after three nights.

I think this is a really interesting find.

We already know that fewer positive emotions have a major impact on mental health.

We also know that poor sleep is included in virtually all mental health diagnoses.”

People are sleeping less and less around the world and the problem has been made worse by the pandemic.

Dr Saksvik-Lehouillier said:

“It’s easy for us to go to bed later than we should, especially when we think, ‘I just have to finish watching this series.’

But we still have to get up to go to work, or study, or deliver our kids to kindergarten.

This contributes to getting too little sleep.

How long we sleep is just part of the picture, but when we sleep is also important.

An irregular circadian rhythm can be worse than sleeping too little.

Going to bed and getting up at the same time is recommended.”

Different people need different amounts of sleep, said Dr Saksvik-Lehouillier:

“Sleep is individual.

Not everyone needs to sleep seven and a half hours every night.

And we’re A and B people.

Some of us like to stay up till the wee hours, others love to rise and shine early in the morning.

The most important thing is how you feel.

If you’re in a good mood and alert when you get up, those are indications that your sleep habits are working for you.”

The study was published in the journal Sleep (Saksvik-Lehouillier et al., 2020).

Dementia: The Optimal Sleep Time That Reduces Risk

Alzheimer’s is the most common form of dementia, making up 70 percent of cases.

Alzheimer’s is the most common form of dementia, making up 70 percent of cases.

People who sleep for too little or too long are at a higher risk of cognitive decline and dementia.

However, those who sleep for between 5.5 and 7.5 hours per night do not see declines in their cognitive health, even when suffering the early effects of Alzheimer’s disease.

Alzheimer’s is the most common form of dementia, making up 70 percent of cases.

Poor sleep is a common symptom of Alzheimer’s and can accelerate the progression of the disease.

Dr Brendan Lucey, the study’s first author, said:

“It’s been challenging to determine how sleep and different stages of Alzheimer’s disease are related, but that’s what you need to know to start designing interventions.

Our study suggests that there is a middle range, or ‘sweet spot,’ for total sleep time where cognitive performance was stable over time.

Short and long sleep times were associated with worse cognitive performance, perhaps due to insufficient sleep or poor sleep quality.

An unanswered question is if we can intervene to improve sleep, such as increasing sleep time for short sleepers by an hour or so, would that have a positive effect on their cognitive performance so they no longer decline?

We need more longitudinal data to answer this question.”

The study included 100 people, average age 75, most with no cognitive impairments.

Their cognitive function was tracked over almost 5 years, along with their sleep quality.

Professor David Holtzman, study co-author, explained the results:

“It was particularly interesting to see that not only those with short amounts of sleep but also those with long amounts of sleep had more cognitive decline.

It suggests that sleep quality may be key, as opposed to simply total sleep.”

People suffering sleep problems should be aware that they can be treated, said Professor Beau M. Ances, study co-author:

“I ask many of my patients, ‘How’s your sleep?’

Often patients report that they’re not sleeping well.

Often once their sleep issues are treated, they may have improvements in cognition.

Physicians who are seeing patients with cognitive complaints should ask them about their quality of sleep.

This is potentially a modifiable factor.”

The study was published in the journal Brain (Lucey et al., 2021).

This Sleep Pattern Increases Heart Disease Risk 54%

People who ignore this risk factor increase their odds of developing heart disease or stroke.

People who ignore this risk factor increase their odds of developing heart disease or stroke.

Less than seven, or more than eight hours of sleep can cause arterial stiffness leading to heart disease or stroke.

If you like to stay up late and have a drink or check your emails or watch TV and sleep until mid-morning, remember the quantity of sleep is important for your heart health.

The incidence of arterial stiffness is much lower in people who sleep seven or eight hours a night compared to those who sleep for shorter or longer hours, a study has found.

Consequently, people who sleep more than eight hours or less than seven hours are at higher risk of heart disease or stroke.

A research team measured 1,752 adults’ sleep patterns in Greece and based on duration of sleep they were divided into four groups.

The first was ‘normal’ group meaning their sleep was seven or eight hours per night, the second was the ‘short’ group meaning they slept six to seven hours nightly, the third one ‘very short’ meaning they had less than six hours sleep, and the last group ‘long’ as they had more than eight hours sleep nightly.

The results showed that participants who had more than eight hours a night were at a 39 percent higher risk of plaque build up inside the arteries and for those who slept less than six hours the odds increased to 54 percent.

This shows that duration of sleep is as important as exercise and diet for cardiovascular health.

Dr Evangelos Oikonomou, the study’s lead author, said:

“The message, based on our findings, is ‘sleep well, but not too well.’

Getting too little sleep appears bad for your health but too much seems to be harmful as well.

Unlike other heart disease risk factors such as age or genetics, sleep habits can be adjusted, and even after taking into consideration the impact of established risk factors for atherosclerosis and cardiovascular diseases — for example age, gender, obesity, smoking, hypertension, diabetes, high blood pressure and even a history of coronary artery disease — both short and long sleeping duration may act as additional risk factors.”

Plaque build-up causes the arterial walls to thicken and narrow so the blood flow in the brain and the body will decrease leading to cardiovascular disease or stroke.

Dr Oikonomou, said:

“We don’t fully understand the relationship between sleep and cardiovascular health.

It could be that sympathetic nervous system withdrawal or a slowing [of this system] that occurs during sleep may act as a recovery phase for [usual] vascular and cardiac strain.

Moreover, short sleep duration may be associated with increased cardiovascular risk factors — for example, unhealthy diet, stress, being overweight or greater alcohol consumption — whereas longer sleep duration may be associated with a less active lifestyle pattern and lower physical activity.”

How much sleep we need is related to different factors such as age.

The guidelines for adults are mostly seven to nine hours sleep a night, however, one in three American adults gets less than six hours sleep.

Studies have shown that people who sleep poorly are at greater risk of high blood pressure, heart disease, diabetes, obesity, mental health problem, and early death.

Experts say a regular six to eight hours a night is spot-on.

Dr Oikonomou, said:

“It seems that this amount of sleep may act as an additive cardioprotective factor among people living in modern western societies, and there can be other health benefits to getting sufficient and quality sleep.”

The study was presented at the American College of Cardiology’s Annual Scientific Session Together with World Congress of Cardiology, March 2020.

Waking 100 Times A Night Is Normal And May Indicate Healthy Sleep (M)

The reason for these ultra-short awakenings is partly related to memory, the researchers think.

The reason for these ultra-short awakenings is partly related to memory, the researchers think.


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