A new study published in the Nov 4 2008 issue of British Journal of Cancer suggests that sleeping for less than six hours per night may increase risk of breast cancer in women.

Early studies show that night shift female workers are more likely than those who work daytime to acquire breast cancer due probably to the poor sleep quality.

The study led by Kakizaki M and colleagues from Tohoku University Graduate School of Medicine in Senkai Japan found women who slept 6 or fewer hours per day were 62 percent more likely to develop breast cancer.

The researchers did not explain why because their study was not meant to explore the reason why there is an association between shorter sleep duration and higher breast cancer risk.

Kakizaki's study involved 23,995 Japanese women and was intended to examine the correlation between sleep duration and risk of breast cancer.   During the follow-up, 143 women were diagnosed with the disease.

In the United States, breast cancer is diagnosed in 185,000 women and kills 45,000 each year. The disease is largely preventable and sufficient sleep is known to boost immunity against cancer.  Physical activity or exercise is also known to reduce the risk.

Source:

Br J Cancer. 2008 Nov 4;99(9):1502-5.

Sleep duration and the risk of breast cancer: the Ohsaki Cohort Study.

Kakizaki M, Kuriyama S, Sone T, Ohmori-Matsuda K, Hozawa A, Nakaya N, Fukudo S, Tsuji I.

Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.