Medical Problems

The detrimental effect of bad lighting is now so serious that the American Medical Association has called for a national effort on light pollution, stating that "many species (including humans) need darkness to survive and thrive" [PDF]. The AMA also states:

"Light trespass has been implicated in disruption of the human and animal circadian rhythm, and strongly suspected as an etiology of suppressed melatonin production, depressed immune systems, and increase in cancer rates such as breast cancers."

Increased Cancer Risks

There is now significant evidence showing that exposure to light at night can disrupt the body's production of melatonin, a brain hormone best known for its daily role in resetting the body's biological clock. Secreted primarily in the brain, and at night, melatonin triggers a host of biochemical activities, including a nocturnal reduction in the body's production of oestrogen. Research has shown that decreasing nocturnal melatonin production increases an individual's risk of developing oestrogen-related malignancies, such as breast cancer.

For more details, see:

Psychological Stresses

Living within the arctic circles can exhibit psychological stresses on inhabitants, due to the 24-hour daylight in summer, and 24-hour darkness in winter. Suicide rates in Finland are one of the highest in the world. Many would guess that the 24 hours of darkness would be the most stressful time, but apparently not. The thesis of Dr Helina Hakko states: "A significant excess of total suicides was found during spring/summer (May-July) and a significant trough during winter/spring (December-March) months.". The 24-hour daylight appears to cause more stress and suicides than at any other time of the year. For more information, please look at Dr Helina Hakko's PhD thesis.

Medical Problems in Children...

Other health problems can occur in children. Scientists have warned that children who sleep with a light on during the night could be ruining their eyesight (see this BBC News story). US scientists found that children who sleep with a light on are significantly more likely to grow up short-sighted and having to wear glasses, when compared to children who sleep in the dark.

Research sponsored by a power company found that exposure to constant artificial light may reduce levels of melatonin, which regulates the body's internal clock, and the Circadian cycle (see the BBC News article). Dr Chris Idzikowski, director of the Sleep Assessment and Advisory Service, said that leaving lights on at night "...could lead to a disruption of sleeping patterns, hyper-activity and may have a negative impact on a child's health."

Other medical problems...

It is well documented that excessive light can lead to a chronic lack of sleep, diminishing the effectiveness of the body's immune system; indeed, shining light is a common method of torture: "Ill-treatment also reported to Amnesty International include prolonged sleep deprivation, inadequate exercise provision, prolonged restraint in painful positions, sometimes combined with exposure to loud music, and exposure to 24-hour lighting." (click here for the full press release).

For more information...

There are many hundreds of references dealing with biological clocks, circadian rhythms, melatonin, and the effects of light at night on animals and plants - see the IDA's "Photobiology & Pathology" page. More information about the deterious effects of lighting on human health can be found on the webpage.

Additional related items

January, 2010
BBC News: Harvard tests reveal why light can worsen migraines
"The visual pathway that underlies a migraine sufferer's sensitivity to light has been uncovered by Harvard scientists. "

April, 2005
BBC News: EU pollution deaths cost billions
"The European Union could save up to 161 billion euros a year by reducing deaths caused by air pollution, the World Health Organization has said. Transport and the use of fossil fuels in homes [used to generate needless light pollution] are the major contributors to air pollution."

March, 2005
The Guardian: The power of darkness
"Artificial light illuminates our lives, allowing us to work or play through the night. But, as Hugh Wilson discovers, we toy with our body clocks at severe risk to our wellbeing."

December, 2004
Reuters/Yahoo News: Night Shift Linked to Late Pregnancy Loss
"Pregnant women who regularly work the night shift may have an increased risk of a miscarriage late in pregnancy or a stillbirth, a new study suggests. According to [University of Aarhu's Jin Liang] Zhu's team, the link between pregnancy loss and steady overnight work may have to do with estrogen levels. Exposure to light at night suppresses the normal nighttime release of the sleep-related hormone melatonin, which in turn is believed to spur an increase in other hormones, including estrogen."

May, 8th, 2003
BBC News: Darkness never falls for children

October 17th, 1998
Science News Online: Does light have a dark side

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