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(2004): 588-596.

Recent research into sleep and the way sleep patterns are affected by light suggest that sleeping in complete darkness is much more beneficial than sleeping in less than complete darkness (Pauley, 2004). Similarly, regular exposure to certain types of artificial lighting can have a negative effect on the quality of sleep as well. Research into the comparative health of daytime and nighttime workers has helped establish some of the more specific ways that sleep is important to human health. For example, certain forms of cancer (such as breast cancer and colorectal cancer) have been documented at higher rates among nighttime workers (Pauley, 2004). As it happens, those forms of cancer are known to be moderated by Melatonin, a hormone secreted by the pineal gland during specific phases of sleep and known to vary in relation to exposure to light (Pauley, 2004).

Research on mice revealed that melatonin-related cancers increased when the subjects were exposed to very small levels of light during sleep and also that completely blind human beings have a lower incidence of colorectal cancers than blind people who can perceive some light (Pauley, 2004). The researchers eventually determined that nighttime work is detrimental to human health partly because night workers are much less likely to sleep in absolute darkness since they sleep during daylight hours. Compounding the problem is the fact that the wavelengths common to blue television light and electronic equipment status lights are particularly bad in that regard. The research suggests that it is essential for night workers to sleep in entirely blacked-out rooms.