New Study Links Nighttime Darkness to Success of Breast Cancer Therapy

Sleep scientists and those trying to help insomnia sufferers to get a better night’s sleep have long sung the praises of creating the correct sleep environment, and sleeping in a totally darkened room are always part of the long list of sleep hygiene issues that can be controlled to great advantage. Another light-related issue has been the blue light that emanates from televisions, e-readers and tablets, as it has been proven that they reduce the production of melatonin and disrupt the sleep cycle. Now a study out of Tulane University School of Medicine is strengthening that argument, indicating that exposure to any kind of light at night actually shuts down nighttime production of melatonin and makes breast cancer therapies less effective. The group specifically looked at the impact that light has on the effectiveness of tamoxifen, a popular breast cancer drug, and found that it rendered the therapy of little use. The study was titled, “Circadian and Melatonin Disruption by Exposure to Light at Night Drives Intrinsic Resistance to Tamoxifen Therapy in Breast Cancer”.  The researchers investigated the role of melatonin – a hormone whose production is in response to the presence or absence or light, and which has a significant impact on the body’s sleep cycle – and its role in tamoxifen’s effectiveness.  They exposed lab animals implanted with breast cancer cells to different dark light cycles to determine how the cancer responded. According to Steven Hill, one of the study’s principal investigators, “In the first phase of the study, we kept animals in a daily light/dark cycle of 12 hours of light followed by 12 hours of total darkness (melatonin is elevated during the dark phase) for several weeks. In the second study we exposed them to the same daily light/dark cycle; however, during the 12 hour dark phase, animals were exposed to extremely dim light at night (melatonin levels are suppressed), roughly equivalent to faint light coming under a door.” What they found was that melatonin alone plays a role in delaying tumor formation but that tamoxifen actually caused the tumors to regress. They also found that animals that slept in complete darkness had higher levels of melatonin than those exposed to dim light. For women who are being treated with tamoxifen for breast cancer, this information is extremely important. Many find themselves unable to sleep, and stay up late reading from tablets or watching televisions, and this may be working against their most effective treatment option.  According to David Blask of Tulane’s Circadian Cancer Biology Group, “High melatonin levels at night put breast cancer cells to sleep by turning off key growth mechanisms. These cells are vulnerable to tamoxifen But when the lights are on and melatonin is suppressed, breast cancer cells wake up and ignore tamoxifen.”