LRC Research: Light and Adolescents


Figueiro et al1 investigated the effect of morning and evening light exposure on DLMO in a group of 8th grade students at a North Carolina school that had plentiful available daylight. Over the course of five consecutive school days, from waking until 15:00, the participants wore specially designed orange-tinted glasses that block light below 525 nm. LRC researchers found that DLMO was delayed by approximately 30 minutes compared to what the students experienced during the previous week when not wearing the glasses. Figueiro and her colleagues repeated this protocol in a between-subjects study, and found that DLMO was delayed by 30 minutes in those who wore the orange-tinted glasses compared to those who did not.

In a separate study, Figueiro et al2 measured DLMO of teenage students in upstate New York in winter and spring, finding that adolescents experience shorter sleep times in spring compared to winter. They also found that exposure to daylight in the evening can delay sleep onset among adolescents. When coinciding with a fixed rising time to accommodate morning school schedules, this delay can result in sleep deprivation.



The impact of self-luminous devices

More than 83% of children and adolescents (age 3-17 years) in the U.S. live in a home with at least one computer.34 Roughly 6 in 10 people use a laptop or computer within the hour before bedtime at least several nights per week.35 According to the 2014 Sleep in America Poll, 16% of children reported reading or sending emails or text messages after initiating sleep.36

Figueiro and Overington3 studied the effect of self-luminous devices (e.g., computers, tablets, cell phones, etc.) on acute melatonin suppression among 20 high school students (age 15-17 years) over two consecutive nights at home. On the first night of this field study, the students wore orange-tinted glasses and worked with self-luminous devices for 3 hours before their normal bedtimes. On the second night, the students wore the orange-tinted glasses only for the first hour of self-luminous device use, and removed them for the rest of the 3-hour period. The study demonstrated that a 1-hour exposure to light emitted from the devices suppressed melatonin by 23% and a 2-hour exposure suppressed melatonin by 38%. These results suggest an increased sensitivity to light for evening acute melatonin suppression among adolescents compared to those in their mid-20s and 30s.

LRC researchers also investigated the effects of tablet use (iPad) on acute melatonin suppression.4 This within-subjects study employed college student participants in three experimental conditions: (1) tablet use at full brightness; (2) tablet use while participants wore orange-tinted glasses; and (3) tablet use while participants wore goggles that delivered 470-nm light at 40 lux. Melatonin suppression from the first condition (tablet-only at full brightness) was 22% after 2 hours.



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