Based on our previous research, we hypothesized that the red light would be useful for promoting workplace alertness without negatively affecting the sleep and the circadian system. One of the interventions explored a novel lighting intervention (red light), delivered to the participants’ retinas via personal light glasses, that was designed to increase alertness and improve performance without disrupting the secretion of melatonin. Our study took place in four hospitals in Albany, NY, Schenectady, NY, South Bend, IN, and Syracuse, NY. We also assessed the lighting’s effect on task performance, activity–rest patterns, and subjective sleep quality. But when experienced at sufficiently high levels at any time of day, both types of light can elicit a beneficial, immediate alerting effect that is similar to drinking a cup of coffee. Blue light suppresses melatonin production at night, while red light does not. In this study, we evaluated the effectiveness of experimental lighting interventions in terms their effects on the participants’ levels of the hormone melatonin, which is produced in darkness and prepares the body for sleep. Long-wavelength light, on the other hand, has negligible effects on the circadian system and is perhaps best visualized as the red sky at twilight that is followed by sleep. Short-wavelength light is the most-effective of all light sources for stimulating the circadian system, perhaps best visualized as the blue light of the morning sky that energizes us for the coming day. Although several properties of light are known to influence the timing of the circadian system, a key property for our study is a light source’s spectral composition, or its wavelength. The circadian system’s main synchronizer is the 24-hour pattern of light and dark reaching our eye retina, which sends those signals via the optic nerve to a cluster of cells in the brain’s hypothalamus region called the master biological clock, which in turn regulates circadian rhythms. Because the human circadian system runs on a cycle that, for most people, is slightly longer than the solar day, it must be continually synchronized to keep the right things happening at the right times. Research conducted over the last 40 years has found a strong link between health problems and disruption of the human circadian system, which regulates our bodily processes like sleeping by producing circadian rhythms that basically signal the body to do the right things at the right times. Sinai and Rensselaer Polytechnic Institute examined the effects of an experimental lighting intervention on levels of melatonin, task performance, activity–rest patterns, and subjective sleep quality.

To make matters more complex, nurses typically follow 12-hour shift schedules and can perform crucial tasks (e.g., monitoring unstable patients, etc.) when alertness levels are low and the pressure for sleep is high. Studies show that healthcare workers are at greater risk for shift-work-related health and safety problems compared to their colleagues who work conventional daytime hours. These risks are especially acute for those who work rotating shifts that involve working through the night, as sometimes occur in hospitals. Shift work has been linked to poor sleep, chronic metabolic disorders (e.g., cardiovascular disease, diabetes, and obesity), several forms of cancer, depression, and elevated risk for the occurrence of accidents.

Night shift nurses experiment 01