October 25, 2011
Skin Cancer Threat May Be Less During The Morning Hours
A new study, published in the Proceedings of the National Academy of Sciences suggests that exposure to ultraviolet (UV) rays in the morning hours may be less harmful than the sun´s ray´s in the afternoon.
The study, performed on mice because they have a similar circadian rhythm to humans only opposite, found that mice exposed to UV radiation at 4 am had a 500 percent increase in the incidence of skin cancer than those exposed to UV radiation at 4pm.
Since the 24 hour biological clocks of mice and humans run counter to each other, scientists conclude that humans would have less incidence of cancer when exposed to early morning UV radiation.
Dr. Aziz Sancar of the University of North Carolina, and the senior author of the study says, “Therefore, our research would suggest that restricting sunbathing or visits to the tanning booth to morning hours would reduce the risk of skin cancer in humans. However, further studies in humans are needed before we can make any definitive recommendations.”
The researchers link the difference in incidence to a protein called XPA. This protein is found to be responsible for repairing DNA damaged by UV radiation. The levels of XPA rise and fall throughout the day following the circadian rhythm.
Dr. Kat Arney, of Cancer Research UK, told the Telegraph, “Over the past few years, scientists have been gathering evidence showing that DNA repair is linked to the cell´s biological clock, and these new findings in mice support this idea. But we don´t know whether this research will hold up in humans, and we would still advise people to avoid using sunbeds or getting sunburnt at any time of day to reduce the chances of developing skin cancer.”
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