Sleep

No not the quote from Hamlet “To sleep, perchance to dream” but how lack of sleep can impact on your health; sleep cycle explained and how sleep patterns have changed.

The Mayo clinic linked a lack of sleep to an increase in abdominal fat. An unhealthy find. During this study participants had free access to food, which coupled with the lack of sleep contributed to their increase in abdominal fat.

Findings from a randomized controlled crossover study led by Naima Covassin, Ph.D., a cardiovascular medicine researcher at Mayo Clinic, show that lack of sufficient sleep led to a 9% increase in total abdominal fat area and an 11% increase in abdominal visceral fat, compared to control sleep. Visceral fat is deposited deep inside the abdomen around internal organs and is strongly linked to cardiac and metabolic diseases.

Journal of the American College of Cardiology,

We all know how tired and grumpy we can become after a night or several nights poor sleep. Science has shown how poor sleep can effect your health from weight gain to a weakened immune system or with chronic deprivation it can cause high blood pressure, diabetes, heart attack, heart failure or stroke, obesity, depression, reduced immune system function and lower sex drive.

Your body needs sleep, just as it needs air and food to function at its best. During sleep, your body heals itself and restores its chemical balance. Your brain forges new thought connections and helps memory retention. Sleep deprivation leaves your brain exhausted, so it can’t perform its duties as well. During sleep your immune system produces infection fighting substances like antibodies and cytokines that combat bacteria and viruses.

When you don’t get enough sleep, your body releases more of the stress hormone cortisol. In excess amounts, cortisol can break down skin collagen, the protein that keeps skin smooth and elastic. Hence the aged appearance from lack of sleep.

The types of sleep

In addition to the number of hours slept it is important to get the right kind of sleep. During the night the total sleep is made up of several rounds of the sleep cycle. Not all sleep cycles are the same length, but on average they last about 90 minutes each and vary from person to person.

There are four sleep stages, one for rapid eye movement (REM) and the others for non-REM sleep. Stage 1 is essentially a “dozing off” stage. The body hasn’t fully relaxed, and there are light changes in brain activities. It is easy to awake during this stage.

In Stage 2, the body temperature drops, the muscles relax and there is a slowed breathing and heart rate. Eye movement stops and the brain activity slows but shows short bursts of activity. This sleep can last for 10-25 minutes at first and increase during the night. Collectively this makes up more than half the sleep time.

Stage 3 is known as deep sleep. It is harder to wake a person. The muscle tone, pulse and breathing rate decrease as the body relaxes. However the brain activity shows an identifiable pattern known as delta waves, which helps the brain create and store new memories and improves its ability to collect and recall information. Deep sleep usually occurs during the first half of the night, initially lasting for 20-40 minutes. These stages become shorter the longer you sleep and more time is spent in REM sleep.

Sleep Trackers

Wearable devices or under the pillow devices rely on sensors to detect physical signs like heart rate and body movement as opposed to lab based sleep tests that use sensors to measure brain activity. The sleep trackers upload the data to a device that analyse and display the results. Although not as accurate as a lab based sleep test, these devices and apps can help to raise awareness of your sleep patterns.

How many hours sleep?

It is generally thought that an adult body needs 7-8 hours sleep a night but there is a lot of historical evidence that humans used to sleep in two distinct chunks. Historian Roger Ekirch of Virginia Tech published a book “At Day’s Close: Night in Times Past” found more than 500 references to segmented sleeping patterns in diaries, court records, medical books and literature, from Homer’s Odyssey to an anthropological account of modern tribes in Nigeria.

He describes that a first sleep began about two hours after dusk, followed by waking period of one or two hours and then a second sleep. During this waking period people were quite active. They often got up, went to the toilet or smoked tobacco and some even visited neighbours. Most people stayed in bed, read, wrote and often prayed. Countless prayer manuals from the late 15th Century offered special prayers for the hours in between sleeps. And these hours weren’t entirely solitary – people often chatted to bed-fellows or had sex.

A doctor’s manual from 16th Century France even advised couples that the best time to conceive was not at the end of a long day’s labour but “after the first sleep”, when “they have more enjoyment” and “do it better”. Anyone care to confirm this?

Ekirch found that references to the first and second sleep started to disappear during the late 17th Century. This started among the urban upper classes in northern Europe and over the course of the next 200 years filtered down to the rest of Western society. By the 1920s the idea of a first and second sleep had receded entirely from our social consciousness. He attributes the initial shift to improvements in street lighting, domestic lighting and a surge in coffee houses. 

 So if you lie awake in the middle of the night, read on to discover the forgotten medieval habit of ‘two sleeps’.