Like to read before bed? Make sure it's a 'real' book: Bright light from Kindles and iPads other smartphones and tabs keep us awake, study warns

Snuggling up with a good book in bed has long
been seen as a way to wind down at the end of
the day.
But scientists have discovered that the millions
who read their bedtime stories on an iPad or a
Kindle Fire are actually keeping themselves
awake.

They found that people who regularly read
electronic books before lights out sleep for fewer
hours.
This is because the blue glow emitted by the
electronic devices can destroy the body's natural
rhythm. All living things have an internal
mechanism – known as the circadian rhythm, or
body clock – which synchronises bodily functions
to the 24-hour pattern of the Earth's rotation.
The clock is regulated by the senses, most
importantly, the way the eye perceives light and
dark.


This mechanism rules our daily rhythms, including
sleep and waking patterns and metabolism. It
also determines whether we are a 'morning' or an
'evening' person.
But the pressures of modern living mean many of
us now increasingly work against our body clocks
– with disrupted sleep thought to be partly
responsible for increased rates of cancer,
dementia and diabetes.
During the two-week study, 12 participants read
electronic books for four hours before bedtime.
The experiment was then repeated with printed
books.


The researchers found that those reading on
screens were less sleepy in the evening and took
longer to fall asleep.



They had reduced levels of melatonin, a hormone
which plays a role in inducing sleepiness.
And they took nearly ten minutes longer to fall
asleep after reading an e-reader compared to
reading a printed book. They also had a lower
amount of rapid eye movement sleep – a stage
thought to be crucial because it is when
memories are consolidated.

The study was carried out by Penn State and
Harvard universities in the US and published in
the Proceedings of the National Academy of
Science.
Lead researcher Dr Anne-Marie Chang said
screens can have an 'extremely powerful effect'
on the body's natural sleep pattern.
She added: 'Participants reading a light-emitting
eBook took longer to fall asleep and had reduced
evening sleepiness, reduced melatonin secretion,
later timing of their circadian clock and reduced
next-morning alertness than when reading a
printed book.'


Dr Charles Czeisler from Harvard University, who
contributed to the study, added: 'In the past 50
years, there has been a decline in average sleep
duration and quality.


'Since more people are choosing electronic
devices for reading, communication and
entertainment – particularly children and
adolescents who already experience significant
sleep loss – research evaluating the long-term
consequences of these devices on health and
safety is urgently needed.'



(source:dailymail.co.uk)