Exposure to light from computers or smartphones at night could lead to weight gain
Artificial
light has transformed how the human race has lived in the past 100
years or so. It's estimated that between 1950 and 2000, exposure to
artificial light in the UK rose four-fold. Even for those not working
night shifts, it can be almost impossible to avoid the night-time glare
from street lamps, car lights, TVs, computers and smartphones.
light has transformed how the human race has lived in the past 100
years or so. It's estimated that between 1950 and 2000, exposure to
artificial light in the UK rose four-fold. Even for those not working
night shifts, it can be almost impossible to avoid the night-time glare
from street lamps, car lights, TVs, computers and smartphones.
Now
there are growing concerns that constant exposure to light when it's
dark damages our health by disrupting our circadian rhythm - the body's
built-in clock. Artificial light affects the production of melatonin, a
hormone released by the pineal gland in the brain.
there are growing concerns that constant exposure to light when it's
dark damages our health by disrupting our circadian rhythm - the body's
built-in clock. Artificial light affects the production of melatonin, a
hormone released by the pineal gland in the brain.
Melatonin triggers feelings of sleepiness and is released when it gets dark, with levels peaking at around 2am.
During
the day, exposure to sunlight stimulates a nerve pathway from the
retina (the light-sensitive area at the back of the eye) to an area in
the brain called the hypothalamus, which is the control centre for the
body clock.
the day, exposure to sunlight stimulates a nerve pathway from the
retina (the light-sensitive area at the back of the eye) to an area in
the brain called the hypothalamus, which is the control centre for the
body clock.
The
incoming signals help control hormones, body temperature and other
functions that play a role in making us feel sleepy or wide awake.
incoming signals help control hormones, body temperature and other
functions that play a role in making us feel sleepy or wide awake.
Once
this area receives a signal from the eye that the day has broken, it
halts the release of melatonin from the pineal gland. When the sun goes
down and darkness occurs, it tells the pineal gland to start releasing
the hormone again.
this area receives a signal from the eye that the day has broken, it
halts the release of melatonin from the pineal gland. When the sun goes
down and darkness occurs, it tells the pineal gland to start releasing
the hormone again.
As
well as triggering sleepiness, melatonin has other crucial roles,
including keeping blood pressure and blood sugar levels healthy.
well as triggering sleepiness, melatonin has other crucial roles,
including keeping blood pressure and blood sugar levels healthy.
'Bright
light at bedtime suppresses melatonin production, so is probably going
to delay sleep and affect the body clock,' says Professor Jim Horne,
former head of sleep research at Loughborough University. 'But some
people are more sensitive to it than others.'
light at bedtime suppresses melatonin production, so is probably going
to delay sleep and affect the body clock,' says Professor Jim Horne,
former head of sleep research at Loughborough University. 'But some
people are more sensitive to it than others.'
Repeatedly
delayed or broken sleep has been found to raise the risk of heart
attacks by up to 50 per cent and strokes by 15 per cent. So how could
artificial light be harming your health without you realising?
delayed or broken sleep has been found to raise the risk of heart
attacks by up to 50 per cent and strokes by 15 per cent. So how could
artificial light be harming your health without you realising?
Piles on the pounds
Scientists
at Northwestern University in Chicago recently found exposure to light
from computers or smartphones at night could lead to weight gain. Even
charging a phone by your bedside could have an effect.
at Northwestern University in Chicago recently found exposure to light
from computers or smartphones at night could lead to weight gain. Even
charging a phone by your bedside could have an effect.
They
discovered exposure to such light increases hunger pangs that can last
several hours, even if a meal was eaten that evening.
discovered exposure to such light increases hunger pangs that can last
several hours, even if a meal was eaten that evening.
One
reason may be that laptops and phones tend to emit more blue light, the
kind that usually acts as a wake-up call for the brain and tells our
body clock it's time to get up.
reason may be that laptops and phones tend to emit more blue light, the
kind that usually acts as a wake-up call for the brain and tells our
body clock it's time to get up.
Though we usually see light as white, it is made up of seven colours - violet, indigo, blue, green, yellow, orange and red.
Exposure to blue light - the kind from smartphones, tablets and laptops - could leave you feeling drowsy
The beam produced by ordinary light bulbs does contain blue light but it's less concentrated than in some modern devices.
The
study found being exposed to blue-enriched light (the kind smartphones
produce) for three hours in the evening stimulated appetite, possibly by
tricking the body clock into thinking it was the start of the day and
time to replenish its energy stores with food.
study found being exposed to blue-enriched light (the kind smartphones
produce) for three hours in the evening stimulated appetite, possibly by
tricking the body clock into thinking it was the start of the day and
time to replenish its energy stores with food.
This
is because melatonin also helps to suppress levels of ghrelin, a
hormone that increases appetite, while stimulating the release of
leptin, a hormone that reduces food cravings.
is because melatonin also helps to suppress levels of ghrelin, a
hormone that increases appetite, while stimulating the release of
leptin, a hormone that reduces food cravings.
'A
small amount of blue light is not likely to have much effect on sleep
or health,' says Professor Horne. 'But the brain is more sensitive to
blue light than any other colour and it does tend to affect the body
clock more than other light colour.'
small amount of blue light is not likely to have much effect on sleep
or health,' says Professor Horne. 'But the brain is more sensitive to
blue light than any other colour and it does tend to affect the body
clock more than other light colour.'
Recent
studies found female hamsters repeatedly exposed to fairly low levels
of light at night showed signs of low mood and depression
studies found female hamsters repeatedly exposed to fairly low levels
of light at night showed signs of low mood and depression
May increase the risk of cancer
Occasional
use of devices late at night is unlikely to cause any harm. But
repeated exposure has been linked with an increased risk of cancer.
use of devices late at night is unlikely to cause any harm. But
repeated exposure has been linked with an increased risk of cancer.
A
recent report in the European Journal of Cancer Prevention featured
findings from scientists who analysed 16 studies on light exposure at
night.
recent report in the European Journal of Cancer Prevention featured
findings from scientists who analysed 16 studies on light exposure at
night.
The
researchers, from a Chinese university, found that repeated light
exposure - most of the studies involved night workers - increased the
risk of breast cancer in women by 17 per cent.
researchers, from a Chinese university, found that repeated light
exposure - most of the studies involved night workers - increased the
risk of breast cancer in women by 17 per cent.
But
only 'high' artificial light, such as the glare from phones or laptops,
semed to have this effect. Ambient lighting which illuminated a wider
area, such as a bedside lamp, did not appear to significantly increase
the risk.
only 'high' artificial light, such as the glare from phones or laptops,
semed to have this effect. Ambient lighting which illuminated a wider
area, such as a bedside lamp, did not appear to significantly increase
the risk.
Other
studies found nurses who work nights are at a higher risk of the
disease and that light exposure makes some tumours resistant to one of
the main weapons against the disease - breast cancer drug tamoxifen.
studies found nurses who work nights are at a higher risk of the
disease and that light exposure makes some tumours resistant to one of
the main weapons against the disease - breast cancer drug tamoxifen.
It's
not clear why artificial light at night might have this effect - one
theory is that by disrupting the natural hormone balance in the body it
creates the right environment for cancer cells to flourish.
not clear why artificial light at night might have this effect - one
theory is that by disrupting the natural hormone balance in the body it
creates the right environment for cancer cells to flourish.
Another
suggestion is that reduced melatonin output at night allows an increase
in levels of another hormone, oestrogen, which is involved in the
development of two in every three cases of breast cancer.
suggestion is that reduced melatonin output at night allows an increase
in levels of another hormone, oestrogen, which is involved in the
development of two in every three cases of breast cancer.
Baby mice exposed to light at night from a young age displayed more signs of stress
Makes children more anxious
Animal
research suggests night-time exposure to artificial light could make
children more anxious. A study in the journal Physiology and Behaviour
found baby mice exposed to light at night from a young age displayed
more signs of stress and anxious behaviour than those sleeping in dark
conditions - possibly by increasing levels of stress hormones such as
cortisol.
research suggests night-time exposure to artificial light could make
children more anxious. A study in the journal Physiology and Behaviour
found baby mice exposed to light at night from a young age displayed
more signs of stress and anxious behaviour than those sleeping in dark
conditions - possibly by increasing levels of stress hormones such as
cortisol.
Another
study, published last month, found children may be more susceptible to
melatonin suppression from night light than adults.
study, published last month, found children may be more susceptible to
melatonin suppression from night light than adults.
Scientists
at Kyushu University in Japan found that while 46 per cent of grown-ups
exposed to light at night saw a significant drop in melatonin
production, in children the figure was 88 per cent. Researchers said:
'The percentage of melatonin suppression by light in children was almost
twice that in adults.'
at Kyushu University in Japan found that while 46 per cent of grown-ups
exposed to light at night saw a significant drop in melatonin
production, in children the figure was 88 per cent. Researchers said:
'The percentage of melatonin suppression by light in children was almost
twice that in adults.'
Raises the risk of type 2 diabetes
Artificial
light from charging smart phones or tablets by the bed may not be the
only problem. Some studies suggest lights in other parts of the house
are a risk.
light from charging smart phones or tablets by the bed may not be the
only problem. Some studies suggest lights in other parts of the house
are a risk.
Research
in the journal Chronobiology International found elderly people were
much more likely to develop diabetes if they sat under bright lights for
four hours before they went to bed, rather than dimmer ones.
in the journal Chronobiology International found elderly people were
much more likely to develop diabetes if they sat under bright lights for
four hours before they went to bed, rather than dimmer ones.
Japanese scientists looked at 513 men and women in their 70s and found the brighter the bulbs, the lower the melatonin level.
When
they examined type 2 diabetes rates they found those exposed to
brightest lights in the evening were 50 per cent more likely to develop
the disease. This may be because the body clock also has a role in
controlling blood sugar levels.
they examined type 2 diabetes rates they found those exposed to
brightest lights in the evening were 50 per cent more likely to develop
the disease. This may be because the body clock also has a role in
controlling blood sugar levels.
One
solution, says Professor Horne, may be to switch to red light bulbs.
'The body clock is not so sensitive to red light so if you want to avoid
adverse effects of light at night then it is an option.'
solution, says Professor Horne, may be to switch to red light bulbs.
'The body clock is not so sensitive to red light so if you want to avoid
adverse effects of light at night then it is an option.'
Could give you the blues
A
restful night's sleep is meant to do the power of good. But exposure to
night-time light could have the opposite effect on mental as well as
physical health.
restful night's sleep is meant to do the power of good. But exposure to
night-time light could have the opposite effect on mental as well as
physical health.
Recent
studies at Ohio State University found female hamsters repeatedly
exposed to fairly low levels of light at night showed signs of low mood
and depression.
studies at Ohio State University found female hamsters repeatedly
exposed to fairly low levels of light at night showed signs of low mood
and depression.
Scientists
found hamsters exposed to dim light had higher blood levels of tumour
necrosis factor (TNF), a protein that usually sends messages in response
to injury or inflammation.
found hamsters exposed to dim light had higher blood levels of tumour
necrosis factor (TNF), a protein that usually sends messages in response
to injury or inflammation.
Constant
exposure to raised TNF levels has also been linked with depression
because it tends to be picked up by receptors in the hippocampus, an
area of the brain that not only regulates the body clock but that is
also involved in regulating mood.
exposure to raised TNF levels has also been linked with depression
because it tends to be picked up by receptors in the hippocampus, an
area of the brain that not only regulates the body clock but that is
also involved in regulating mood.
Drowsiness in the daytime
Exposure
to blue light - the kind from smartphones, tablets and laptops - could
leave you feeling drowsy the next day, even if you get a good night's
sleep. That's the conclusion of a recent study at Tsukuba University in
Japan, where nine men were exposed to either blue light or no light for
two hours before bed. Although they slept for similar times, the next
morning researchers found higher levels of drowsiness among those shown
the blue light.
to blue light - the kind from smartphones, tablets and laptops - could
leave you feeling drowsy the next day, even if you get a good night's
sleep. That's the conclusion of a recent study at Tsukuba University in
Japan, where nine men were exposed to either blue light or no light for
two hours before bed. Although they slept for similar times, the next
morning researchers found higher levels of drowsiness among those shown
the blue light.
Their
metabolisms were slower, suggesting light had disrupted the body
clock's ability to kick-start things in the morning. This could be
linked to a fall in melatonin levels in the night.
metabolisms were slower, suggesting light had disrupted the body
clock's ability to kick-start things in the morning. This could be
linked to a fall in melatonin levels in the night.
Read more: http://www.dailymail.co.uk/health/article-2800593/how-light-night-make-ill-scientists-learn-effects-of.html#ixzz3GjaeQv7L
