Sleep Hygine is a phrase used to describe behaviours and environmental factors that are designed to help improve sleep.  Like most things we do they tend to go better if we plan them. Most people do have a routine they follow when they go to bed and, although the routines can be quiet flexible, some things can distrupt it significantly. 

The body has it’s own routine based in the natural day-night cycle called the circaidian rhythm and everyone’s circaidian rhythm is slightly different.  The average length of the circaidian rhythm is 24.25 hours[1].  It turns out that night owls have longer circaidian rhytms, while early risers have shorter rhythms.

[1] http://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side

As we mentioned in the last post the body has a “Master Clock” (the technical name is the suprachiasmatic nucleus or SCN) that regulates the circaidian rhythm.  Recently it has been discovered that the SCN recieves input directly from the eye, and can measure intensity of light hitting the back of the eye or retina.  In the SCN dim light stimulates the production of melatonin, the hormone that helps induce sleep (among other things but more about that later).

The cells in the retina that send signals about light intensity to the SCN are not involved in vision directly.  They go by the hidiously long name of Intrinsically Photsensitive Retinal Ganglion Cells (IPRG cells), which basically tells you where they are and what they do.  They sit in the back of the eye, and detect light.

The interesting thing about these cells is they are particularly sensitive to blue light. 

An English[1] study of several electronic devices looked at what kind of light they put out.  They studied three devices; an ipad Air, a Kindle, and an iPhone 5s.  They measures the light output across the visible spectrum and came up with this graph.

[1] http://journal.frontiersin.org/article/10.3389/fpubh.2015.00233/full

As you can see there is a spike of blue light emitted by all devices relative to other colours. 

It’s important to note here that it’s not just electonic tablets, and smart phone who have screens that emit lots of blue light.  LCD TV’s and LED bulbs do too.  It’s important to note here that it’s not just electonic tablets, and smart phones who have screens that emit lots of blue light.  LCD TV’s and LED bulbs do too.

So what?

Remember earlier we mentioned that melatonin was used by the body to help induce sleep, and that the SCN triggers melatonin production in low light conditions.  It turns out that when you shine blue light (around the 460nm range) on IPRG cells they are twice as effective at inhibiting melatonin production as when you shine green light (around 555nm) on them.  So it appears that IPRG cells use the intensity of blue light to determine how strongly to inhibit or stimulate melatonin production.  Lots of blue light = strong inhibition and the opposite too.

A study conducted in the US[1] exposed subjects to blue light during “sleep hours” showed (amongst other  things) a significant decrease in melatonin production.  Another group conducted a study[2] comparing reading a book, or a light emitting device (tablet, smart phone, or really anything with a screen) at bedtime.  They found that people who read from the electronic devices

[1] http://www.journalsleep.org/Articles/290206.pdf

[2] http://www.scientificamerican.com/article/q-a-why-is-blue-light-before-bedtime-bad-for-sleep/

• Took longer to go to sleep
• Had less REM (dreaming) sleep
• Took longer to wake up after an 8 hour sleep
• Were sleepier after an 8 hour sleep,

than people who read a book.

So what about melatonin?

As we said before melatonin production is stimulated by low light conditions.  Melatonin is present in very low levels during the daytime, and production increases as bedtime approaches (remember about early birds and night owls) and peaks in the middle of the sleep cycle.

Melatonin does more than signal the body to prepare for sleep.  It also appears to help protect against oxidative stress[1], and radiation damage[2], as well as influencing several other important body systems.

Melatonin has been used for many years in the US as a treatment for mild insomnia, and for preventing jet lag.

Melatonin is a prescription medicine in New Zealand.  But there are ways of both increasing melatonin in the diet, and increasing the body’s own production.  Many common foods contain vaying amounts of melatonin, unfortunately about 80% of an oral dose of mealtonin gets metabolised by the liver, and lost in urine.

Table 1

Some examples of melatonin content in plants and foods[3]

Plant/food

Melatonin

Tomato

3–114 ng/g

Walnuts

3–4 ng/g

Cereals (rice, barley)

300–1,000 pg/g

Strawberry

1–11 ng/g

Olive oil

53–119 pg/ml

Wine

50–230 pg/ml

Beer

52–170 pg/ml

Cow's milk (unprocessed)

3–25 pg/ml

Nighttime milk

10–40 ng/ml

Despite this relatively low usabilty of melatonin absorbed from the gut, a radomised controlled study[4] that show significant elevation in melatonin levels in samples as well as improve sleep scores, after dosing with tart cherry.

The pathway the body uses to make it’s own melatonin is rather complex, and requires several essential amino acids (essential amino acids have to come from the diet as we can’t make our own), magnesium, vitamin B6 (Pyridoxine), folic acid, 5HTP, and SAMe (s-Adenosylmethionine).  So if you want to try increasing your body’s production of melatonin you’ll need plenty of these.

So back to sleep hygine.  If you are having trouble getting to sleep, or don’t seem to be able to get enough sleep trying not using screens for an hour to half an hour before going to bed.  If you like reading in bed, read a book.  If you can’t get away from them turn down the intensity of the screen on the electronic device you use.

If you’re still struggling come in and talk to us.

[1] http://www.ncbi.nlm.nih.gov/pubmed/22507555

[2] http://www.ncbi.nlm.nih.gov/pubmed/18643846

[3] Food Nutr Res. 2012; 56: 10.3402/fnr.v56i0.17252.

[4] http://www.ncbi.nlm.nih.gov/pubmed/22038497