Figure 2From: Implications of controlled short-wavelength light exposure for sleep in older adultsEstimation of threshold dose at different exposure durations using the difference between melatonin concentrations in the dark and at 0.7 μW/cm2 as well as the difference between melatonin concentrations in the dark and at 2 μW/cm2. The asterisk indicates a statistically reliable difference at p = 0.05.Back to article page