The Ageing Eye is Incompatible with Conventional LED Lighting

Because of social isolation, infirmity and dementia, a significant proportion of elderly people are confined mostly indoors. This includes over 2 million Americans who reside in assisted living facilities and nursing homes, largely lit by conventional LED and fluorescent lighting.

Not only do they lose the lifespan- and healthspan-extending benefits of regular morning daylight exposure, but they are exposed to artificial lighting that gets progressively less healthy as we age.

It is not the lights that are changing. Rather it is the progressive yellowing of the lenses in our eyes, and the unfortunate uneducated choice of 450 nm blue pump LED lighting that makes it increasingly unfit for purpose the older you get.

Readers of this Substack newsletter, and my book THE LIGHT DOCTOR, will know that the timing and the amount of 480 nm sky-blue light that enters your eyes each day is critical for your health and well-being. 480 nm is the peak sensitivity of the blue detecting receptors in the eye1 - the intrinsically photosensitive retinal ganglion cells (ipRGCs), and exposure to this wavelength in the morning robustly synchronizes our circadian clocks and boost our health and well-being.

Outdoor daylight provides a rich source of this critical 480 nm blue light. But, as we have discussed, conventional LED lights instead have a royal blue spike at about 450 nm and a big dip in their spectrum at around 480 nm - the so-called cyan gap. The chart above shows that the 450nm blue from conventional LEDs has only 70% of the effectiveness of 480 nm blue tuned to our biological need. The reality is that these LEDs are designed for lumens per watt energy efficiency without any consideration of their negative health impact.

In contrast, healthy circadian lighting uses a 480 nm blue peak during the day that is tuned to the spectral sensitivity of the circadian system.

These failures in the design of conventional LED lights are a problem even when you are young. But as you age this mistuning of blue light gets has even worse effects. As the years pass by the lenses in our eyes progressively grow yellower. As this happens, these lenses within our eyes block more and more of the lower wavelength light in the violet and blue range. This effect is most pronounced the lower the wavelength. Hence the reduction in the transmission of 450 nm wavelengths is much larger than that of 480 nm wavelengths.2

We can read from the chart below that by the age of 70, only 23% of 450 nm blue light reaches the retina of the eye. In contrast, 42% of 480 nm light falls on the retina, because it is less impacted by lens yellowing.

When you multiply the relative circadian clock synchronizing effectiveness of 480 nm versus 450 nm light by the wavelength dependent effect of the ageing lens, you will find that at age 70 only 16% of 450 nm light gets through to the retina, whereas 42% of 480 nm blue light reaches the blue detectors in the 70-year-old person’s eyes.

By using 450 nm blue-rich conventional LED lighting we are placing our elderly in a depressing world of unhealthy biological dimness, thereby hastening their “shuffle off this mortal coil” as Shakespeare would say.3

And as I would say “it is time to change your lights” and the lights of your elderly loved ones.

The quickest way to understand the importance of healthy lighting and outdoor daylight exposure, and the value of nocturnal darkness is to read my book THE LIGHT DOCTOR.

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