A. There was a recent report that suggested that exposure to light at night may be a cause for the increased incidence of childhood leukemia. However, this was not really a research report and was simply a discussion among childhood leukemia specialists at a medical conference in London. There is some research behind this idea, including that adult night shift workers, who have an increased exposure to bright lights at night, have an increased risk of breast cancer and colorectal cancer. But it seems a far stretch to concluded that the dim light from a child's night light could have the same effect.
To be sure, the rate of childhood leukemia has been increasing. According to the National Cancer Institute monograph, Cancer Incidence and Survival among Children and Adolescents: United States SEER Program, 1975-1995, the average annual rate of childhood leukemia has risen almost 1% a year from 1977 to 1995, mostly because of an increase in rates of acute lymphoblastic leukemia or ALL.
Looking at the numbers more closely leads one to question the link to night lights though. For example, while the overall rate of ALL increased at a rate of about 1% per year for white children, there was almost no increase in ALL rates for black children. Do white children use night lights so much more frequently than black children, and if not, then why doesn't using a night light have an affect on the rate of leukemia for black children?
Also, the average annual rates for ALL peaked in 1990 and then steadily went down over the next few years. Were more parents using night lights just before that time and then decided to use them less frequently afterwards?
Then there is the fact that the incidence of leukemia is highest when children are two to three years old. Plenty of older toddlers and preschool age children continue to use a night light, so why isn't the rate higher for them too?
Since the increase in cancer rates from exposure to light at night is supposed to be caused by abnormal melatonin levels, one simple study that could be done is to see if children who use a night light actually have abnormal levels of melatonin.
And it would be helpful to know if childhood leukemia rates are higher in children that live in the 'Land of the Midnight Sun,' or Artic and near-Artic Regions where they experience constant daylight for two months out of the year or areas where it just doesn't get very dark at night.
Unfortunately, not much is known about what puts a child at risk for developing ALL. Among the known risk factors are a:
- male sex
- age less then 5 years
- white race
- higher socioeconomic status
- prenatal diagnostic x-ray exposure
- postnatal ionizing radiation exposure
- genetic conditions, such as Down syndrome, neurofibromatosis, Shwachman syndrome, and others
Still, it is not a good idea for preliminary talk or research to be released to the public like this story was. All that does is cause parents to worry unnecessarily or make unneeded changes in their child's routine. There is usually a good reason for having a night light on in your child's room. Getting rid of it may raise your child's fear of the dark and cause trouble getting them to sleep.
Even the association between night lights and myopia or nearsightedness was made by a single research report that worried many parents, even though later reports found that the link wasn't true.
So at this point it is probably okay to still use a night light and not make your child sleep in the dark.
