Artificial Light at Night Contributes to Prostate
Cancer and Breast Cancer Say Researchers
Theories for cause: suppression of melatonin
production, suppression of immune system, body's
biological clock confused between night and day
Feb. 3, 2009 Countries with the highest levels of
artificial light at night also have the highest rates of prostate
cancer, according to researchers that earlier found a similar link with
breast cancer.
The new study from the University of Haifa, Haifa,
Israel found the risk of prostate cancer increased as much as 80 percent
for men living in countries with the highest levels of artificial light
at night.
The study was by Prof. Abraham Haim, Prof. Boris A.
Portnov, and Itai Kloog of the University of Haifa, together with Prof.
Richard Stevens of the University of Connecticut. It was intended to
examine the influence of various factors - including the amount of
artificial light at night - on the incidence of three types of cancer:
prostate, lung, and of the large intestine, in men around the world.
Data was collected from a database of the
International Agency for Research on Cancer, on the incidence of these
types of cancer in men in 164 countries. Data on the levels of lighting
at night were gathered from DMSP (Defense Meteorological Satellite
Program) satellite images.
The nighttime illumination data were adjusted by
the geographic distribution of the population of the country, in order
to reach an accurate measure of "the amount of artificial light per
night per person."
The researchers also examined additional factors,
such as electricity consumption, percentage of urban population,
socioeconomic status, and other variables.
At the very first stage of the study, it already
became clear that there is a marked link between the incidence of
prostate cancer and levels of nighttime artificial illumination and
electricity consumption. Several different methods of statistical
analysis were used to arrive at this conclusion.
Next the researchers isolated the "amount of
artificial light at night per person" variable in order to examine its
particular effect.
The countries were divided into three groups for
this stage of the study:
● those with little exposure to lighting at night;
● those with medium exposure; and
● those with high exposure.
The results demonstrated that the incidence of
prostate cancer in those countries with low exposure was 66.77 prostate
cancer patients to 100,000 inhabitants.
An increase of 30% was found in those countries
with medium exposure: 87.11 patients per 100,000 inhabitants.
The countries with the highest level of exposure to
artificial light at night demonstrated a jump of 80%: 157 patients per
100,000 inhabitants.
This joins a previous finding by the same
researchers that was published in Chronobiology International in
2008, that exposure to artificial lighting at night increases the
incidence of breast cancer in women.
According to the researchers, there are a number of
theories that could explain the increased incidence of prostate cancer
due to exposure to lighting at night, such as suppression of melatonin
production, suppression of the immune system, and an effect on the
body's biological clock because of confusion between night and day.
Whatever the cause, there is a definite link between the two, they say.
"This does not mean that we have to go back to the
Middle Ages and turn the lights out on the country. What it means is
that this link should be taken into account in planning the country's
energy policies," the researchers pointed out.
The researchers added that an increased use of
artificial lighting is considered by the World Health Organization as a
source of environmental pollution. As such, the appeal made by Israel's
Ministry of Environmental Protection to use energy-efficient lighting is
problematic, as this type of lighting is also much brighter. The country
should encourage energy saving in lighting as well as limiting the
pollution level, according to the researchers.
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Feb. 3, 2009 Countries with the highest levels of
artificial light at night also have the highest rates of prostate
cancer, according to researchers that earlier found a similar link with
breast cancer.