by April McCarthy
July 15, 2016
Humans have long created artificial lights by burning or heating
materials, however lighting systems today are far more invasive to
the human body than those of the past.
According to a new study reported in the
Cell Press journal, many negative health consequences result from
constant exposure to artificial light.
evolved with the electromagnetic frequencies from the sun and
the earth, and these frequencies are considered essential to all
life. Life itself synchronizes and harmonizes with these
But what happens when these frequencies
are disrupted by modern technology?
With the growing use of
energy saving lamps and the development of new lighting
technologies, comes the long-term concern that some people who have
conditions that react to light might be negatively affected by this
Previous research by Northwestern
scientists showed that people
who received the majority of their bright light in the morning
weighed less than those who were exposed to most of their bright
light after 12 p.m.
The researchers wanted to understand why.
Mouse studies also have shown that mice
kept in constant light have altered glucose metabolism and gain
weight compared to control mice.
"Our study shows that the
light-dark cycle is important for health," says Johanna
Meijer of Leiden University Medical Center in the Netherlands.
"We showed that the absence of
environmental rhythms leads to severe disruption of a wide
variety of health parameters."
Those parameters included
pro-inflammatory activation of the immune system, muscle loss, and
early signs of osteoporosis.
The researchers say that the observed
physiological changes were all indicative of "frailty" as is
typically seen in people or animals as they age.
But there was some more encouraging
"The good news is that we
subsequently showed that these negative effects on health are
reversible when the environmental light-dark cycle is restored,"
To investigate the relationship between
a loss of the light-dark cycle and disease, Johanna Meijer
and colleagues, including Eliane Lucassen, exposed mice to
light around the clock for 24 weeks and measured several major
Studies of the animals' brain activity
showed that the constant light exposure reduced the normal rhythmic
patterns in the brain's central circadian pacemaker of the
suprachiasmatic nuclei (SCN) by 70 percent.
Strikingly, the disruption to normal
light and dark patterns and the
circadian rhythm led to a reduction
in the animals' skeletal muscle function as measured in standard
tests of strength.
Their bones showed signs of
deterioration, and the animals entered a pro-inflammatory state
normally observed only in the presence of pathogens or other harmful
After the mice were returned to a
standard light-dark cycle for 2 weeks, the SCN neurons rapidly
recovered their normal rhythm, and the animals' health problems were
The findings suggest that more care
should be taken in considering the amount of light exposure people
get, particularly those who are aging or otherwise vulnerable.
That's important given that 75 percent
of the world's population is exposed to light during the night.
Constant light exposure is very common
in nursing homes and intensive care units, and many people also work
into the night.
"We used to think of light and
darkness as harmless or neutral stimuli with respect to health,"
"We now realize this is not the case
based on accumulating studies from laboratories all over the
world, all pointing in the same direction. Possibly this is not
surprising as life evolved under the constant pressure of the
We seem to be optimized to live
under these cycles, and the other side of the coin is that we
are now affected by a lack of such cycles."
The bottom line, according to the
researchers is "light exposure matters."
They say they now plan to perform more
in-depth analysis of the influence of distorted light-dark cycles on
the immune system. They'd also like to investigate possible health
benefits to patients exposed to more normal conditions of light and
There are two groups of patients who react abnormally to light:
The part of the spectrum that plays the
main role is UV light, so the main concern is with light sources
that emit UV, such as CFLs.
The severity of these diseases varies
widely between patients and the amount of UV required to produce
symptoms is also variable:
Polymorphic light eruption (PLE):
Usually affects females and
flares up in spring or early summer and results in an itchy,
red, spotty rash on skin exposed to sunlight. For most
patients, artificial light sources do not induce this
actinic dermatitis (CAD):
This affects males over 50 years
of age and results in sensitivity to various allergens, to
UVA, UVB and also visible light for some patients. UV from
artificial light could induce the disease in people with
moderate or severe CAD.
This uncommon disease happens
all year round but is particularly bad in spring and summer.
Skin exposed to sunlight develops itchy, red and inflamed
Severe cases may be at risk from
CFLs or other UV-emitting sources.
This skin disorder affects both
males and females and if it develops into a generalized
urticaria, it can result in anaphylactic shock, so it can be
Severely affected patients may
be at risk from CFLs and unfiltered halogen sources
producing UV/visible radiation.
This is a rare disease that
affects both sexes and produces blisters and scarring on
skin exposed to sunlight. Low energy artificial light
sources that emit UVA, can affect some patients.
This affects all age
groups in both sexes and arises in people who produce
antibodies against the breakdown products of their own cells
so patients are susceptible to agents that cause cell death.
Some drugs and factors
such as UV (mainly UVB) exposure can induce this disease. At
least some patients are at risk from long-term exposure to
UV from CFLs and unfiltered halogen lamps.
Are a rare group of diseases
that are inherited but are also induced by environmental
factors and all relate to the accumulation of the
photosensitive pigment porphyrin within the skin.
Artificial light sources,
including incandescent bulbs, can cause skin reactions and
even burns in the most sensitive patients.