New research suggests that chronic exposure to artificial light may increase the risk of childhood leukemia, due to a disruption of the body’s internal clock.
The possible link between artificial light and childhood cancer was presented by British and U.S. researchers at the First International Scientific Conference on Childhood Leukemia in early September. Working shifts and being exposed to light at night, when the body’s clock says it should be sleeping, has been associated with an increased risk of breast and colon cancer in previous studies.
Russell Foster, a molecular neuroscience professor at London’s Imperial College pointed out the uncertainty in the association of artificial light and leukemia, but in the context of what is known about other forms of cancer, he said it is not unreasonable to investigate the connection.
|The Big Picture|
There's no hard proof yet that nightlights cause leukemia, but scientists do know that exposure to light at night disrupts your body's internal clock and suppresses production of the hormone melatonin, an antioxidant that can protect your DNA from damage that leads to cell mutation and cancer.
Childhood leukemia has risen by more than 50% in kids under age 5 in the last 50 years. The cause of the disease is unknown, but it is believed to be triggered by a combination of genetics and environmental factors. Certain chemicals, ionizing radiation, electromagnetic fields, and viruses and infections have been blamed for causing leukemia. Now some researchers are considering adding artificial light to that list.
Today, as compared to 100 years ago, people are exposed to much more light during evening hours when the body should be producing melatonin. Exposure to light shuts off melatonin production, therefore disturbing the body’s circadian rhythms. Studies have shown that a disruption in normal melatonin production can lead to certain cancers.
Melatonin’s effects on the body are not completely understood, but some lab and animal studies have shown that it might offer cells some oxidative protection, which means that low levels of melatonin could reduce the body’s cancer-fighting abilities. Cancer develops when abnormal cells duplicate uncontrollably and develop into tumors.
Professor Foster’s suggestion of an association between light at night and leukemia was triggered by his discovery of a new type of light-sensing cell within the eye that regulates circadian system. He also noted a study by researchers involving 118 children who received chemotherapy for a certain form of leukemia. The risk of relapse was 2.5 times higher in the children who received chemotherapy in the morning than those who were given the same treatment in the evening.
Researchers will continue to study how decreased melatonin production affects the body and investigate any links between increases in childhood leukemia and greater exposure to artificial light.