Age-related melanopic equivalent illuminance: Impacts of age, illuminance and correlated colour temperature on non-visual effects for indoor lighting design

The spectral transmittance of ocular media for short-wavelength light is different for different age groups. It is essential to concentrate on the melanopic effects of different ages in lighting design. In this study, an age-related melanopic equivalent illuminance ( E z , n ) was developed to consider the age-dependent reductions in ocular spectral transmittance. To investigate the age-related effects of light, a red–green–blue–cyan–yellow–warm white (R/G/B/C/Y/WW) colour-mixing method based on pulse width modulation LEDs has been introduced and developed. Five optimized mixed-white light spectral power distributions were obtained with correlated colour temperatures (CCTs) of 3000 K, 3500 K, 4500 K, 5000 K and 6500 K and all corresponding general colour rendering indices were at least 96.7. Moreover, standardized multiple linear regression was adopted to analyse the quantitative relationship between important factors (e.g. age, photopic illuminance ( E v ), CCT) and E z , n as well as their interactive effects on E z , n in daytime and sleep environments. These results indicate that the influence of age on circadian effects is strongly modulated by ambient light levels, and show the complex interactions among age, E v and CCT. This work could provide scientific evidence for developing more efficient and personalized age-adaptive lighting solutions.