posted on 2023-11-21, 17:04authored byYun Jae Eo, Sung-woo Choi, Chohui Kim, Seulgee Lee, Chulsoo Yoon, Dae Hwan Kim, Changwook Kim, Young Rag Do
With the inherent sleep and wake cycle regulated by natural
sunlight,
the human body has evolved over millennia to be active during the
day and to rest at night. However, maintaining an optimal 24 h cycle
has become increasingly problematic in modern society as more people
spend the majority of the day indoors. Many research groups have reported
that inadequate artificial lighting interferes with melatonin production
and disrupts the circadian rhythm. This study considered biological
functions for light-emitting diodes (LEDs) of next-generation illumination,
and LED packages and spectra suitable for both daytime and nighttime
applications were designed. The prepared daytime human-centric (HC)-LEDs
had a melanopic/photopic (M/P) ratio that was up to 26% higher than
that of conventional (c)-LEDs, whereas the nighttime HC-LEDs exhibited
up to a 26% lower M/P ratio compared to the c-LEDs. Nevertheless,
because the HC-LED is designed to have almost the same color coordinates
as the c-LED having the same correlated-color temperature (CCT), there
is no change in the perceived color. To substantiate the biological
effect, melatonin level data were obtained from 22 voluntary participants
in c- and HC-LED lighting environments. In the HC-LED lighting environment,
melatonin was suppressed by 21.9% after waking, and nocturnal melatonin
secretion was increased by up to 12.2%. As human-centric lighting,
our HC-LEDs are expected to become an essential element for modern
life, where people spend most of their time indoors.