Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Light emitting device usage during the day. Usage has been approximated by the share of device dependent web page traffic. It has been reported, that blue light exposure up to 4 hours prior to sleep can affect the melatonin levels at night and subjective sleep quality. Figure modified according to 79
