Can light save lives?
Synchronisation of the inner clock
Yes! At least when a person wakes from a coma or artificial deep sleep. Modern intensive care medicine often uses artificial deep sleep for severe conditions, such as COVID-19. After awakening, the patient must enter a circadian rhythm as quickly as possible, within a few days. If this fails, one speaks of delierium. Cognitive impairments persist in about one third of the patients who remain in this temporal and spatial confusion for an extended period. Delirium has a detri-mental prognostic effect and extends hospital stays and recovery times. Approximately one tenth of delirium patients do not recover from this state and subsequently die. Light is used here as a therapeutic agent (remedy) and is the strongest pace-setter for the inner clock.
Recreation room planning example
A recreation room's lighting must meet many requirements. Since care home residents usually spend a lot of time in the recreation room, we selected an HCL design in this example. Human Centric Lighting meets both the minimum requirements for the respective visual task and also fulfils biological needs, in our case those of 75-year-old residents.
Lighting for the day/night rhythm
After an artificial deep sleep or anaesthesia, the re-synchronisation of the "inner" clock must take place as quickly as possible. For this purpose, patients waking up from deep sleep are provided with a high illuminance via the ceiling surface above the bed. The research project "Mimicking natural daylight expositur" of the University of Salzburg in the Albert Schweitzer Clinic in Graz, in which RECOVER luminaires from XAL were installed, resulted in a daily dose of 6,333lx/h measured at the eye. A stabilisation of the day/night rhythm has been clearly demonstrated here. With a daily dose of less than 5000lx/h, no sufficient biological effect can be assumed.
Lighting for retirement and nursing homes
For healthy people, the recommended 1-hour walk outdoors can be sufficient for the synchronisation of the "inner" clock. For people who are bound to indoor spaces, as is often the case with older people, an appropriate artificial light supply must be provided for continuous synchronisation. In the German planning recommendation for biological lighting effects, DIN SPEC 67600, < 250 MEDI Lux in the morning over < 4 hours is recommended for healthy people (MEDI =Melanopic Equivalent Daylight Intensity). This 250 MEDI lux means about 370 visually assessed lux under 4000 K lighting. Age correction factors are defined for different age groups in DIN 5031-100. The opacity of the eye lens increases with advancing age, and at the same time the size of the pupil diameter decreases.
Thus, significantly less light falls on the retina of an elderly person. For a 90-year-old female resident of a nursing home, these two changes result in a correction factor of 0.193. The required 370 lux of a 32-year-old standard observer divided by the age correction factor of 0.193 becomes 1917 lux for the 90-year-old resident.
The requirements of the international lighting standard EN 12464-1 demand only minimum values to enable the visual task to be performed. To provide the light intensity needed for a biological effect, significantly more luminaires are required. Workplaces can be made biologically effective with two to three times the number of luminaires. For old people's homes, about 4 to 5 times as many luminaires are needed. In each case, care should be taken to ensure generous illumination of the ceiling and upper wall surfaces by indirect light components.
Full-spectrum LED: healthy light that is easy on the eyes
XPECTRUM – XAL's new daylight-like full-spectrum LEDs deliver healthy, biologically effective light. The natural daylight spectrum is achieved by reducing the blue light component and increasing the cyan values. This minimises blue light's risk to the eye and sets it at a level similar to daylight. The resulting non-visual, the so-called melanopic light effect, affects numerous bodily functions and is thus partly responsible for better sleep, increased concentration, and well-being.