Evidence that staying up late and sleeping with the light on can cause cancer is to be examined by a royal commission.
The evidence, reported in The Independent on Sunday 18 months ago, also casts further doubt on the safety of radiation from mobile phones and electric power lines. The Royal Commission on Environmental Pollution is to examine the impact of artificial light on health as part of a short study of its effects on the environment to be launched early next year.
The International Agency for Research on Cancer, the foremost international body on the disease, is considering officially labelling night-shift work as a "probable" human carcinogen, after a study found that nurses and flight attendants are more likely to develop breast cancer.
The study is only the latest among many to make the link between exposure to light at night and the disease, which affects one in 10 women and whose incidence is doubling every two decades. Besides showing that it is 60 per cent more common among night-shift workers, they have demonstrated a similar rise among women who stay up late more than two or three times a week. Conversely, totally blind women are only half as likely to contract it.
Groundbreaking research by the National Cancer Institute and National Institute of Environmental Health in the United States grafted human breast cancer tumours on to rats and infused them with blood taken from women during the day, in the early hours of the morning and after being exposed to light at night. The blood taken in darkness slowed the growth of the tumours by 80 per cent, while that taken after exposure to light accelerated it.
Studies have shown that the light at night interferes with melatonin, "the hormone of darkness" which is secreted by the pineal gland at night and both impedes cancers and boosts the immune system. Electromagnetic radiation, given off by power lines, mobile phones and Wi-Fi, has been found to have a similar effect.
Professor Denis Henshaw of Bristol University said that the radiation "suppresses melatonin in the same way as light does".