Evening bright light may delay body clock and extend sleep in people who wake up too early

Bright light stimulation in the evening resulted in a mean increase of total sleep time of more than 1 hour in early morning awakening insomniacs.

• Nine early morning awakening insomniacs were evaluated for their sleep patterns using wrist actigraphy.
• Initial evaluations indicated that the temperature rhythms of these insomniacs were earlier than normal.
• Exposure to bright light (2,500 lux) from 2000 to 2400 hours delayed temperature rhythm markers by 2-4 hours.
• Melatonin phase markers were also delayed by 1-2 hours following the bright light treatment.
• Sleep onset times did not change, but the mean final wake-up time was delayed from 0459 hours to 0611 hours.

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