LEDs have always been an integral part of emerging technologies in health applications. This article lists some examples of its use in various fields to improve human health and well-being.
Daily routine
A circadian rhythm is when our internal biological clock is synchronized with the movements of the external world, such as the movement of the sun across the sky. There is a lot of interest in using LED lighting products to promote sleep that can help us sleep better at night, feel better during the day, and even improve our overall health. During the day, exposure to light containing the appropriate blue wavelengths is especially important to block the production of melatonin, which can help us feel more awake and energized.
However, blue light may damage the retina as described in IEC/EN 62471 Photobiological Safety of Lamps and Lamp Systems. This standard defines a blue light hazard sensitivity curve that peaks at 435~440nm and drops to a negligible value at 550nm, providing exposure limits and Guidelines for measurement procedures.
Blue LEDs are usually composed of blue-violet light (415~455nm) and blue-green light (456~490nm) in roughly equal proportions. Adjusting the ratio to increase blue-green light maximizes the benefits of circadian rhythms, while also minimizing blue light hazards. At least one manufacturer now offers an LED kit with a choice of blue-violet to blue-green ratios depending on the desired color temperature (CCT).
Treatment of ovarian cancer
Animated Dynamics, in conjunction with Purdue University, developed an app that uses infrared (IR) LEDs to help determine whether a particular chemotherapy is working, saving patients from toxic side effects.
This technique uses an infrared LED light source to illuminate biopsies before and after mixed chemotherapy, and then compares the light scatter produced by the two. If no apoptosis (death of tissue cells) is observed, then the Chemotherapy is likely to be ineffective against the actual treatment of the tumor. The initial trial was conducted on ovarian cancer patients, with the goal of using the data to determine which treatments were most likely to stop the disease.
Bacterial inactivation
With the emergence of the new crown epidemic, people's interest in sterilization has surged, and LED manufacturers have responded with products. Most of these products emit short-wave ultraviolet (UVC) rays, creating a potential risk of UV exposure. Nichia recently released a dual-purpose LED product that is harmless to humans. This product provides both white light for general lighting and violet light at 405nm to inactivate bacteria such as Pseudomonas aeruginosa, Staph and E.coli. Figure 1 shows the difference between the emission spectra of common white light emitters and the new Nichia products in the visible spectral range. The peak intensity at 405nm is about four times higher than the blue light peak present in phosphor-converted white LEDs, but in a wavelength that is less sensitive to the human eye.
Independent tests commissioned by Nichia showed that the dual-purpose LED inactivated up to 98.9% of Pseudomonas aeruginosa within 5 hours at an output of 1000lux at 40cm from the surface. Since the light is in the visible range, continuous exposure will not cause harmful effects to the human eye. However, such light sources need to operate for long periods of time to reach their maximum efficacy, which could hinder widespread adoption of the technology. While the technology may be effective against bacteria, it cannot inactivate viruses, including the new coronavirus.
Medicinal cannabis
The topic of how LEDs are used in health applications would not be complete without mentioning medicinal cannabis, as the industry has exploded, so to speak, thanks to the use of LED lighting.
Fluence, the horticultural lighting company owned by Osram, recently released the results of a two-year study, conducted by Fluence in collaboration with Wageningen University and Research and Texas Original Compassionate Cultivation, to determine the effect of increased LED lighting in a greenhouse environment on plant characteristics, such as the yield and concentration of metabolites such as cannabinoids and terpenes. The benefits of even a small increase in yield or efficiency far outweigh the installed cost of optimizing lighting systems, so research in this area is very valuable. This study involving three different cannabis cultivars concluded that high-intensity broad-spectrum (i.e., 400-700nm) supplemental light maximized yield and metabolites, while lower-intensity broad-spectrum lighting had a not much impact on yield, but can still increase metabolite levels.
