We read with great interest the paper “Sleep stage estimationmethods using a camera for home use” by Nochino et al. [ 1 ]. The paper proposed a method of sleep stage (wake, light,deep, and rapid-eye movement (REM)) estimation using anoff -the-shelf camera. Recognizing its potential in providingconvenient daily sleep monitoring for home use, we wouldlike to open a productive discussion concerning the methodologicalerrors and limitations presented in the paper.