A new study suggests sleeping with a night light disrupts the effectiveness of tamoxifen, a common breast cancer drug.
Earlier studies linked night light to depression and increased risk to cancer. Now, a recent study conducted by researchers from Tulane University found that it also affects the performance of the estrogen-blocking medication by making tumors resistant to the drug.
Lead author of the study and Tulane University professor Steven M. Hill observed rats with breast cancer, who received tamoxifen injections, then were left to sleep in a dark cage that was illuminated periodically.
"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," said Hill in the university news release. "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."
The researchers observed the rats in the dim light cage showed lower melatonin levels and bigger tumors that were resistant to the drug. But they also discovered this could be resolved with melatonin supplements, which reportedly caused tumors to shrink, and the drug to be reactivated.
The study concluded melatonin plays a significant role in the formation of tumors, as it delays growth. Researchers also stated women taking tamoxifen must avoid sleeping in dim light or night lights while under medication.
"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," study co-author David Blask added.
Further details of the study were published in the journal, Cancer Research.
