The Cover Page of the 28 May 2016 New Scientist has SLEEP THE GOOD SLEEP as the title.  According to Matt Walker of he University of California, Berkeley, “sleep has been labelled he this pillar of good health, along with diet, exercise.  But that’s underselling it:  sleep is the foundation on which these other two pillars rest.  There is no tissue within the body and no process within the brain that is not enhanced by sleep, or demonstrably impaired when you don’t get enough.”

Besides the well recognized benefits for memory consolidation, repair and growth sleep—or the lack of it— is now though to have a host of other ill effects.  Too little sleep messes with our emotions and our ability to make sound decisions.  It affects our immune systems and appetites, and has been linked to metabolic diseases such as obesity and type 2 diabetes.  Increasingly, a lack of sleep is implicated in mental health problems to include depression, bipolar disorder, schizophrenia, and neurological conditions such as Alzheimer’s disease.  One of the articles even makes the claim that too much sleep can be harmful, but other articles raise issues that seem to contradict this claim.  One of the reasons for this might be due to genetics and individual differences.

To account for these differences, the best rule of thumb is that we should not need an alarm clock to wake up in the morning.  In other words, we should wake up naturally.

Shift work has bad effects on health.  Unfortunately,  the jobs of many people require shift work.  Quantitative estimates of the damage caused by shift work would be useful for these people in determining whether they should seek different types of employment.  Catching up during weekends for lost sleep, although necessary, does not appear to make up for adverse healthy effects.  The thinking is that the dangers here might be comparable to those incurred via shift work.

Here are the phases of sleep.


REM — 25% of sleep at night.  First occurs about 90 minutes after falling asleep, then every 90 minutes.  These phases get longer later in the night.

STAGE 1 — light sleep.  Happens when we first doze off and just before waking.  Typically lasts for up to 7 minutes.  During this phase we’re prone to twitches, or hypnagogic  jerks.

STAGE 2 — deeper sleep.  Lasts up to about 25 minutes.  Brainwaves become slower and researchers can pick up “sleep spindles,” distinct patterns of brainwaves associated with memory consolidation.

STAGE 3 + 4 — final and deepest stages of non-REM sleep.  heart rate slows.  Lasts up to about 40 minutes.  Brain activity switches to “slow waves.”  Less aware of external noises.  If you’re aroused  from this stage of sleep, it can take up to an hour to become fully alert.

One might conclude from these stages of sleep that napping will not be beneficial.  This is not so.  According to a piece by Catherine de Lange a “nano-nap” lasting just 10 minutes can boost alertness, concentration, and attention for as much as 4 hours.  A “nano-nap”  takes 20 minutes and you increase your powers of memory and recall, too.  We are unlikely  to enter deeper stages of sleep, so we’ll avoid the phenomenon known as sleep inertia, which is the groggy feeling that can occur when waking from deep sleep.

Deep sleep does provide the biggest boost to learning.  Opt for a nap between 60 and 90 minutes, says Walker.  His research shows this aids learning by shifting memories from short-term storage in the brain’s hippocampi to lockdown in the prefrontal cortex, like clearing space on a USB memory stick.   In addition to aiding the retention of factual information, longer naps can increase motor memory, which is useful for training skills such as sport or playing a musical instrument.

A longer nap can also improve equanimity.  When we’re feeling emotional, we should try snoozing for 45 minutes or more.  This should take us through a stage of REM sleep, and brain scans of people following a REM sleep nap showed more positive responses to images and to pleasant experiences.

This post will conclude with statistics that can come in handy when conversations lull.

29 % of people in the US take their cellphones into the bedroom and use it when trying to get sleep (this is not a good idea).

34 minutes is the average extra sleep people get per night after drinking sour cherry juice before bed for 7 days.

67% of the time when men dream about people it’s about other men.  Women dream equally about men and women.

1.2  minutes of sleep is lost per night for each cigarette smoked during the day.

5 is the number of minutes it takes us to fall asleep if were sleep deprived.  The ideal is 10-15 minutes.

100 times an hour:  how often someone with sleep apnea might stop breathing in the night.


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