Disruption of circadian rhythmicity – An exploratory study in Poland

• The chronotypes of Polish students was determined in 2005 and again in 2011 years.
• The increase in the number of “owls” and also in the Internet connection was observed.
• If blue light from computer screens induces these changes is under discussion.

A comparison of the ratio of morningness/eveningness among students in the years 2005 and again 2011 in Poland revealed an increase in the number of people preferring evening activity (from 15.5% to 27.5%) and a decrease of morning type individuals. The only factor which undergone a change during this time is the number of personal computers with internet access (from 38.8% to 65.2%). We assume that the shift in the ratio of the chronotypes in both studies may have occurred due to affecting the circadian clock by the blue light emitted by computer screens.