How Much Sleep Is Enough?


How Much Sleep Is Enough?

World Sleep Day: 13/03/2015

How much sleep do we need?
Too little sleep over several nights leaves you tired, unable to concentrate, depressed and anxious. Long term affects increase your risk of diabetes, high blood pressure and obesity, these are the same risk factors for too much sleep.
At the end of 2014, The National Sleep Foundation in the US completed a project analysing all the scientific data to date on the recommended amount of sleep. They concluded:

  • Age 6-9: 9-11 hours per night
  • Teenagers: 8-10 hours per night
  • 18-64: 7-9 hours per night
  • 65+: 7-8 hours per night

How much sleep is good for you?
Margaret Thatcher and Russian President Vladimir Putin reputedly survive(d) on 4 hours sleep a night. Perhaps if they had the recommended amount of sleep according to their age, the New World order would have turned out differently and their decision making skills would have been more balanced!
The Circadian rhythm
Humans evolved in a 24 hour light/dark cycle known as the circadian clock, where any light after darkness fell was unnatural. When we are exposed to light after dusk, daytime physiology is triggered, the brain becomes more alert, heart rate and body temperature go up, and the hormone melatonin is suppressed.
Steven Lockley, Neuroscientist and Associate Professor at Harvard Medical School considers that we are all suffering from “mini jetlag” in our artificially lit world.
In comparison to how we live day to day consider what happens when you go camping, without electric light. When dusk falls you go to bed earlier and get up when it gets light.
This Circadian cycle is essential for optimal health, recent studies of shift workers have shown that circadian disruption may be a carcinogen; in particular, female night workers have an increased risk of breast cancer.
Until recently, scientists were unsure why sleep was entirely necessary, recent research on mice has given us a larger clue that it is essential for preserving and laying down new memories, particularly from the deep sleep cycle. A fascinating sleep fact is that we only use 5-10% less energy in sleep than we do when awake.
Teenagers and sleep
According to neuroscientists, a teenager’s circadian rhythm starts 2 hours after that of adults; a fact that has been instrumental in driving studies into school hours. Unfortunately, this lasts until age 21 for boys and 19 for girls, so no relief just yet! An Oxford University study initiated this year enrolling thousands of 14-16 year olds aims to investigate ways in which neuroscience might improve teaching, learning, and exam results by synchronising school start times with adolescent biology.
This follows a pilot study which was carried out at a Tyneside High School in 2010, where school lessons started at 10am for the 14-16 year olds. After a year of following this pattern the outcome for health and learning was extremely positive. GCSE results went up from 34 % of pupils scoring five A-C grades including English and Maths to 55 %.
Anyone with a teenager can attest to the fact that they often seem grumpy and unfocussed in the morning as we are trying to rush them out the door to start school at 8.30am, when in fact there is a reason for this, they are generally not as tired as we think they ought to be at bedtime but still sleepy in the morning.
But there is a catch; all those people using Kindles, iPads, laptops, smartphones, flat screen TVs after dark, which emit blue light are actually supressing the production of the sleep inducing hormone melatonin.
How to support a healthy sleep cycle:

  • No alcohol 3 hours before lights out
  • Stop eating 2/3 hours before bed
  • Don’t exercise close to bedtime
  • Avoid blue spectrum devices at least an hour before bed
  • Throughout the night we should all pass through several “light sleep- deep sleep- light sleep” cycles. Each cycle takes 90 minutes and you will feel more refreshed when you wake at the end of a cycle. To maximise the chances of this, work out when you want to wake up, then count back in 90 minute blocks to find a time when you want to go to sleep.

This is all very well but if you have a young baby it may be several months or even years before you can put any sleep regime into practise and I sympathise with you; that is a whole other blog subject, stay posted!
For more information on World Sleep Day click here.

Jacky Dixon
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