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Help Prevent Breast Cancer By Having Sufficient Sleep

Apr 17, 2009 by TacticularCancer.com

Previous Studies

The findings of this study validates the findings of two previous prospective cohort studies relating breast cancer and sleep duration (Verkasalo et al, 2005, Wu et al, 2008). Those two studies had also shown a significant decrease in breast cancer risk for those who slept the longest.

It must be noted, though, that another such study (Pinheiro et al, 2006) did not find any such association. The study team pointed out, however, that that study had looked at residential nurses, who underwent rotating-shift work and had varying sleep timings. The findings of that study thus might not be applicable to the general population.

Strengths and Limitations of Study

According to the study team, their research had a couple of strong points. Firstly, it used study subjects from the general population, thus allowing for overall generalization of its findings. In addition, it used the Miyagi Prefectural Cancer Registry, which the study team said is “one of the earliest and most accurate population-based cancer registries in Japan”.

There were also, however, several limitations. Firstly, self-reported sleep data was used, and assessment was also only carried out once. In addition, and probably very significantly, no information on sleep quality, sleep timing, use of sleep medication, or presence of sleep disorders were available. These factors, of course, are very important as they can directly or indirectly affect cancer risk.

Further, the researchers added that they had no information with regard to rotating-shift work or night work, but they felt that would not have affected their findings greatly as more than half of the study subjects were housewives, farmers or retired.

The Sleep Duration – Breast Cancer Link

Why is breast cancer risk linked to sleep duration? The answer could lie in melatonin, which is secreted during night sleep. When a person sleeps fewer hours, less melatonin is secreted, and lower levels of the chemical had previously been associated with increased breast cancer risk.

In addition, melatonin may possess an inhibitory effect on gonadal function, which includes synthetizing and secreting sex hormones. It had also been found to have an antiproliferative effect on breast cancer cells.

The Bottom Line

If the findings from this study are indeed accurate, then there is an immense difference in breast cancer risk between sleeping 4 to 6 hours every night, and just sleeping 1 to 3 hours more each night. In fact, it is more than likely that the protective effects of sufficient sleep also extend to other forms of cancer. 7 hours of sleep a night may thus be a good number to aim for.

Hopefully, in time to come, further research will reveal more information relating sleep and disease risk, with sleep quality and sleep timing being two of the main possibilities.

Main Source

Sleep duration and the risk of breast cancer: the Ohsaki Cohort Study (http://www.nature.com/bjc/journal/v99/n9/full/6604684a.html)

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