By Ruth Kava, Ph.D., R.D., Aubrey Noelle Stimola, Rivka Weiser, Lynnea Mills
Posted: Monday, December 13, 2004

REPORT
Publication Date: December 13, 2004

Introduction
Pediatric Vaccines and Autism    
PCBs in Salmon and Cancer   
Cell Phones Cause Brain Tumors    
Nightlights and Leukemia     
Chemicals in Cosmetics     
Mercury in Seafood Causes Neurological Problems in Humans  
Cheeseburgers and Cardiovascular Disease (CVD)  
Antibiotics Cause Breast Cancer    
Teflon Causes Health Problems in Humans   
Soda Causes Esophageal Cancer    
Dishonorable Mention     
Deodorants, Antiperspirants Cause Breast Cancer 
Plastics Cause Cancer

The Scare:
Leukemia is the most common form of cancer in children in the U.S., affecting 3,000 children annually and accounting for 30% of all childhood cancers. In the most common childhood leukemias, the white blood cells produced by the bone marrow do not properly mature, and thus cannot perform their necessary immunological functions. Instead, these aberrant cells proliferate uncontrollably, crowding out and replacing bone marrow cells that still produce healthy white blood cells, which results in the telltale symptoms of leukemia such as anemia, fever, infections, bruising, and bleeding. The malignant cells are transported via the bloodstream throughout the body, and can cause meningitis, liver and kidney failure, vomiting, joint pain, and other serious damage. The causes of childhood leukemia are not well understood, but general risk factors include heredity, genetic disorders—such as Down’s syndrome or Fanconi’s anemia—chromosomal translocations, ethnicity, geography, past treatment with chemotherapy or immune suppressing drugs, and specific types of infection.(45)

While the survival rate for childhood leukemia has markedly increased in the last 50 years, so too has the incidence of this life-threatening condition of young people (ages 0-14).(46) Thus, there has been speculation that an as yet unidentified environmental factor plays a major role in the development of childhood leukemia, and this has fueled the desire of medical professionals and worried parents alike to get to the bottom of the trend. As such, even the most preliminary study findings result in a media maelstrom in which unscientific assumptions are routinely made, data are manipulated and taken out of context, and facts are confounded. The latest leukemia-related example of this media irresponsibility drew not on a scientific report, but on discussions held at a conference. Ultimately, however, the nature of the reporting resulted in one of the most unfounded health scares of 2004: “Night Light Found to Increase the Risk of Leukemia.”

Where Did the Scare Come From?
In September 2004, a scientific conference on the incidence, potential causes, and prevention of childhood leukemia, organized by a charity organization, Children with Leukemia, was held in the United Kingdom.(47)  Here, scientists presented their latest studies and thoughts for new ones. Several presentations alluded to an unproven hypothesis that increased light at night (not nightlights specifically), may contribute to the rising incidence of leukemia in children. Since few conclusive studies have been performed on this topic, most of these statements drew on findings from peripherally related studies indicating, if anything, that the hypothesis may be worthy of further investigation. The suspicion has the following ideas at its roots.

There have been many studies of the genes involved in the regulation of circadian rhythms—internal body clocks that regulate the roughly 24-hour cycle of biological processes in all animals. This rhythm, which is rigidly linked to daily cycles of light and darkness, is crucial to determining and maintaining patterns of sleep and waking, hormone production, cognitive functions, mood, eating, cell regeneration, and programmed cell death.(48) Based on results seen in some experiments, the disruption of circadian rhythms, either by mutation of or interference with the normal functioning of these “clock genes” by an outside influence, may be involved in cancer causation.(49)

Separate studies have linked the hormone (and antioxidant) melatonin to both tumor suppression and to the protection of DNA from the oxidative damage caused by free radicals—which sometimes results in carcinogenesis. Correspondingly, a lack of melatonin has been implicated in cancer initiation and progression.(50) However, the details of melatonin’s role in human biology are yet to be understood, and much more research on this topic is needed.

Melatonin levels in the body, which are strongly linked to and regulated by circadian rhythms, tend to be low during the day and high at night.(51) It has been demonstrated that intense light at night suppresses nocturnal melatonin levels.(52-54)     

The relationships of light to circadian rhythms, circadian rhythms to melatonin, and melatonin to cancer have led some researchers to suspect that the differences between the amount, intensity, and constancy of light in the industrialized world and that of the natural solar cycle with which humans evolved may be contributing to the increase in various cancers. In a nutshell, some scientists are seeking to prove that since A is related to B, B is to C, and C to D, then D is related to A. Some studies have already investigated this particular hypothesis. For example, in 2001 Stevens et al. attempted to show that circadian disruption by light in the “built environment” plays a role in endocrine disruption and breast cancer.(55) A 1998 study implied that the chronic jetlag (a common cause of circadian rhythm disruption) experienced by long-term Finnish female flight attendants was responsible for their high rate of breast cancer.(56) Still others have reported that long-term nightshift workers exposed to bright lights have a higher level of colorectal cancer.(57) However, as we will see, these studies by no means warrant a leap to the notion that nightlights are dangerous.

The Media Coverage:
The nightlight-leukemia scare was covered by the following media outlets: CBS, NBC, MSNBC, Medical News Today, Web M.D., and various other health-related web sites. Though coverage was minimal, mistakes made by the media when it comes to nightlights’ relationship to leukemia are three-fold and indicate larger problems in science reporting. First, reports on health information by the press often take the same path as communications in the game of “telephone,” in which a legitimate message is warped through miscommunication, misinterpretation, poor translation, and, sometimes, purposeful manipulation. The further out of its appropriate context the information is taken, the less it resembles its original form and the more meaning is lost. At the end of the line when the final recipient recites the message out loud, the message is distorted beyond recognition. For example, the notion discussed at the conference that increased light at night may play a role in cancer etiology, does not equal, as the media implies, that any light source, wavelength or duration puts every child at risk, and that there are no other variables worth considering. Lost in translation is the fact that “may be a factor in” and “associated with” are not synonymous with “is a factor in” and “causes.” A case-in-point is a news report reposted on Medical News Today entitled “Night Light Found to Increase the Risk of Leukemia.” The wording of this headline strongly suggests proof, yet scientists have specifically said there is none.(58,59) The same article also claims that “the healthiest environment for your child at bedtime would be a pitch black room.”

Second, while scientists can justifiably attempt to piece together various study findings to create novel hypotheses and experiments that may confirm links between conditions and potentially influencing factors, the best scientists are aware of the need for numerous and replicable studies that test a variety of variables before definitive conclusions can be made. They generally understand that correlation does not equal causation, and avoid leaping to conclusions. The media, however, does exactly that, and all too often. Take, for example, the headline on NBC: “Using Nightlights Could Lead to Leukemia.”(60) Despite including a statement that “scientists say they don’t have proof yet that nightlights cause leukemia,” the NBC headline leads readers to believe that confirmation is imminent, when, in fact, we are at stage one of exploring what is merely conjecture. They fail to mention the preliminary nature of this assumption, and that no actual studies of nightlight use and leukemia incidence have been performed.

Another media outlet guilty of assuming that correlation equals causation is CBS. They too assume that if light at night disrupts circadian rhythm, and thus lowers the presumed cancer-preventer melatonin, that it only makes sense that nightlights and leukemia are related. They even mention the studies on nightshift workers and cancer incidence as evidence of grounds for concern. However, they fail to explain that that these studies involved long-term exposure to light intensities that far exceed that emitted by nightlights.(61)

Third, the media failed to distinguish between a preliminary talk and a well-documented peer-reviewed scientific report. This is less an issue of blatant scaremongering and more a case of ignorance about the scientific process in general, but it is just as irresponsible. There are stages to studies, beginning with hypotheses that must be tested repeatedly before definitive conclusions can be made. In addition, studies presented at conferences generally have not yet been published or extensively peer-reviewed. Presenters at the Children with Leukemia conference introduced to their colleagues what they thought were subjects worthy of further study given their research experience. In the context of the preliminary stages of scientific inquiry, this kind of conjecture is reasonable. The tone of the media reports, however, convey that there is a large body of evidence from which to draw conclusions about the relationship of nightlights to leukemia, and that this conclusion has been confirmed by scientists.

The Bottom Line:
The bottom line is this: the recent rise in childhood leukemia incidence justifies investigation as to its cause. However, there is currently no reason to believe that nightlights pose any danger to children (unless, of course, the bulb is really hot or they eat it). While the assertions made by scientists at the Children with Leukemia conference have some peripherally related research as a foundation—such as the studies of increased cancer incidence in nightshift workers—it seems a stretch to conclude that nightlights pose a risk.

The kind of studies needed before recommending that parents ensure total darkness as their children sleep are apparent. For example, do children who use nightlights have abnormal levels of melatonin? If the theory is true, one would expect this to be the case. And what about children who live in areas of the world where near-constant daylight is experienced a few months of the year? What about children who live in urban environments where is it never really pitch dark? Is there a higher incidence of leukemia in these groups of children?

And should we also be fearful that any other factors that disrupt circadian rhythms and suppress melatonin levels might put us at risk for cancer? The media could have just as easily reported as dangerous jetlag, crossing time zones, falling asleep with the light on, insomnia, various drugs (including caffeine), or any other factor that can cause sleep deprivation.

Based on the available evidence, there is no known reason for families to change their customary habits of nightlight use. The use of nightlights can be very reassuring to children who are afraid of the dark, and using a nightlight (or turning on regular lights) when people need to move around the home during the night can help prevent injury. There is no scientific justification for asking people to give up the very real benefits of nightlights because of hypothetical concerns about possible links between exposure to light and leukemia.

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