Our normal sleep wake cycle that is timed to daylight hours is actually an essential component of good health. Besides the fact that the stress that may disrupt sleep cycles is deadly to us, night shift work may have a direct effect on cancers rates via a hormone called melatonin.
Melatonin is a hormone produced deep in the brain (the pineal gland) and helps to regulate our sleep / wake cycle among other things. Sunlight hitting the back of the retina shuts down the production of melatonin. Thus,e the onset of nighttime will allow the body to release more melatonin as less sunlight is no longer hitting the retina.
The research linking melatonin levels, night shift work and cancer has been mounting for several years now and includes:
- Night shift work increases the risk for breast cancer.
- A mere 1 hour of light exposure in the middle of the night affects cell division.
- Higher blood levels of melatonin led to lower risk of breast cancer.
This particular study adds further evidence to the equation, looking at the levels of 6-sulfatoxymelatonin levels (a derivative of melatonin):
- 6-Sulfatoxymelatonin levels were 62% lower in night shift women when they slept in daytime.
- FSH and LH were 62% and 58% higher, respectively, in night shift working women sleeping in daytime.
- When night shift workers did sleep at night, they had 42% lower 6-sulfatoxymelatonin levels.
- At night, while working, 6-Sulfatoxymelatonin levels were 69% lower than daytime workers sleeping at that time.
- FSH and LH were 35% and 38% higher, compared with day shift workers in nighttime sleep.
Overall, it is clear that not sleeping at night will lower the levels of the protective hormone melatonin, while at the same time increasing levels of reproductive hormones that may increase the risk for cancers such as breast. Add this risk on top of women who do not sleep well at night due to stress related sleep problems and you’ve got a recipe for disaster.