Photo/IllutrationThe Radiation Effects Research Foundation in Hiroshima's Minami Ward (Sonoko Miyazaki)

  • Photo/Illustraion

Women from Hiroshima and Nagasaki who had their first periods around the time of the atomic bombs are at an increased risk of developing breast cancer, a study has found.

The findings by researchers from Japan and the United States were released by the Radiation Effects Research Foundation (RERF) on Oct. 15, and published in the U.S. academic journal Radiation Research in the same month.

Past studies have revealed patients have a higher risk of breast cancer when they start menstruating earlier or receive doses of radiation in their early years.

Alina V. Brenner, a senior scientist at RERF, said the correlation between onset of menstruation and radiation exposure ages and the radiation-derived risk suggests breast tissue is more sensitive to radiation around the emergence of secondary sexual characteristics.

In the latest study, RERF tracked 120,000 hibakusha atomic bomb survivors and non-hibakusha, and analyzed radiation doses received and the ages of women suffering from breast cancer when they had their first period.

The results showed a 70-year-old woman who first menstruated at the age of 15 and was affected by radiation at 30 has twice as high risk of breast cancer as radiation-free individuals, while the risk for a 70-year-old female survivor who had both a radiation dose and her first period at 15 is 2.4 times higher than non-hibakusha.