Non-visual spectral sensitivity to light (melatonin suppression).

<p><b>A.</b> Melatonin suppression in young (n = 5) and (<b>B</b>) older participants (n = 8) is represented in percentage control adjusted (%CA). In both young and older groups short (420 nm) and long wavelengths lights (>560 nm) have a limited effect on melatonin suppression. Using a four parameter Gaussian fitting procedure, peak sensitivity is found at 484 nm in the young (blue fit curve, R² = 0.94 and p<0.01 on raw values; R² = 0.81 and p<0.05 on log-transformed values)and 494 nm in the older participant (red fit curve, R² = 0.90 and p<0.01 on raw values; R² = 0.89 and p<0.01 on log-transformed values). <b>C.</b> Comparison of spectral sensitivity in young (blue fit curve) and older subjects (red fit curve). Older subjects show an altered spectral sensitivity of melatonin suppression compared to young subjects. Sensitivity to light in the older is similar in the short wavelength region of the spectrum (<500 nm), but higher for 500–590 nm, and with a shift of peak sensitivity from 484 nm (young) to 494 nm (older).