Glasses Can Help Trick Circadian System

Donning orange glasses to block daylightmay be the answer for teenagers who havetrouble getting up for school in the morningand falling asleep at night. Researchers saidthat the sleep problems may be due to a conflictbetween the teens' internal clocks and thenormal 24-hour solar day.

Mariana Figueiro, PhD, of the RensselaerPolytechnic Institute's Lighting Research Center,explained that individuals need to resettheir internal clocks to synchronize them to thelight and dark cycles of the solar day. Thisresetting happens when individuals sleep untiltheir bodies wake naturally, about 90 minutesafter reaching their core body temperature, andthen expose themselves to daylight. One problem,however, is that some teens may notachieve their normal minimum core temperatureuntil 9 ^AM, when they are already at school,without the chance for exposure to daylight.

Therefore, when teens are awakened by analarm clock and leave for school before reachingtheir core temperature, their circadian systemis out of sync and may interfere with thebody's normal adjustment of the internalclock. Dr. Figueiro suggested that teens' melatonin levels may be the reason why theydo not reach their core temperature until latemorning. Some teens' melatonin levels at 1 ^AMare similar to melatonin levels usually experiencedduring daylight hours, observed Dr.Figueiro. She and her colleagues proposedthat teens wear orange glasses to block daylightwhen they leave for school. It will keeptheir circadian system in darkness until theirbodies catch up.