Current LED lighting technology has proven advantages in being highly efficient, saving energy, and offering a long lifetime. Coupled with smart control and communication technology such as the Internet of Things, LED lighting systems can provide Human Factor Lighting (HFL) by leveraging tunable sunlight, color temperature, and wavelength to produce the correct light for different applications and user groups at different times. HFL allows a user to perform at optimum levels both physiologically and psychologically. For those who spend 90% of their time indoors, the flexible application of LED lighting can better meet their needs in different situations, such as improving circadian rhythms, enhancing the quality of work and sleep, and making people feel safer.
“Exposure to the appropriate light at the right times is conducive to better health. It allows people to fully rest when it is time to rest so that they can focus on work when needed with improved concentration,” said Yahui Chiang, deputy project manager of the Electronic and Optoelectronic System Research Laboratories at the Industrial Technology Research Institute.
Light not only provides people with visual color and perception of light and shade, it also impacts our non-image forming (NIF) visual system, which communicates directly with our circadian biology and affects the secretion of melatonin by the pineal gland at night. Since ancient times, human beings have started work at sunrise and rested at sunset. Our circadian rhythms are adjusted by sunlight. We need high-intensity stimulation during the day but should avoid light environments with high-intensity, high color temperature, or high physiological stimulus at night so as not to affect the production of melatonin. Artificial lighting at night is common and contributes to improper light environments that affect human physical health. Recorded references have found that in cities where artificial lighting is extensively used at night, relatively more people develop illnesses such as circadian rhythm disorders and sleep disorders, and even greater rates of breast cancer for women.
Yahui Chiang further explained how light affects the circadian rhythms via factors such as light intensity, wavelength, and time of exposure. LEDs used for artificial lighting can be adjusted for light intensity and color temperature according to the circadian rhythm, but are sometimes unable to meet physiological and psychological needs at the same time. According to the CIE S 026 standard issued by the International Commission on Illumination, the dominant wavelength of the spectrum that affects the circadian rhythm is blue light at a wavelength of 480nm. Correctly adjusting the 480nm blue light for night lighting is an important factor in improving physiological health.
Yahui Chiang suggested using the artificial spectrum of "same color temperature and different physiological stimuli" to accurately adjust the artificial light environment to the circadian rhythm. Tuning it to meet the lighting needs of different light spectrums during the day and night can reduce interference with melatonin production from the nighttime light environment and help improve the quality of sleep.
Different spectra drive human physiological responses in different ways. As defined in the CIE S 026 standard, the higher the circadian action factor (CAF) value, the more it inhibits the production of melatonin in the human body, which keeps people awake. On the other hand, a low CAF value will prevent a light source from excessively inhibiting the secretion of melatonin and regulate the circadian rhythm.
Driven by the trend where new-generation LED applications focus on lighting for heath, different light environments are made possible for different places and work requirements. Take office buildings featuring white light for example: to optimize the work efficiency of office workers who spend long hours indoors, circadian rhythm-based lighting is called for by tuning the metameric wavelength of the light to adjust the CAF value. Exposure to lighting with warmer colors at work is believed to facilitate performance. Increasing the CAF value in the morning can further improve work efficiency, while gradually lowering the CAF value after noon can ensure productivity enabled by high-color temperature lighting and approximate the circadian rhythms of the workers.
According to experts from the HFL Laboratory of the Industrial Technology Research Institute, healthy lighting is also suitable for shift-based professionals. For example, nursing personnel on duty at a hospital nursing station usually finish work at midnight and need to rest right after they return home. Therefore, the nursing station lighting for the final two hours before the end of the shift should be switched to low-CAF white light to avoid improper artificial lighting affecting the secretion of melatonin at night. During times that require focus, white light with a high CAF value is needed to help maintain alertness and thus increase work efficiency.
In a nursing home, since the eyes of the elderly are less receptive to blue light stimulation, they are prone to insufficient blue light reception during the day, which adversely affects their circadian rhythms. They tend to doze off in the evening but cannot sleep at night. Therefore, tunable lighting technology employing luminaires with a high color temperature and high illuminance during the day can improve their circadian rhythms as well as their quality of sleep.
Light is not only for visual functions, it also has an impact on health. With the importance of the circadian rhythm to human health garnering more attention, the LED industry is starting to launch products aimed at creating a safe, comfortable, and healthy light environment. Yahui Chiang pointed out that healthy lighting products must provide lighting of the same brightness and offer different physiological stimuli and as a result are relatively pricey. In addition, the healthy lighting industry, which purports to uphold health as its core, needs to invest more money and time to obtain related certifications from the FDA and other institutions. In the future, with relevant regulations such as the healthy lighting standard and IWBI's WELL standard, healthy lighting options are expected to emerge as popular lighting trends.