NIOSH Training for Nurses on Shift Work and Long Work Hours

Using Light to Promote a Better Morning Wake-Up Time and Sleepiness in the Evening (Continued)

• You do not need to be in the light during the entire sensitive period in the morning; it is possible that intermittent exposure can be sufficient for you. More research is needed to determine the best times, light levels, and durations of light exposure. But current research indicates shifts in the circadian rhythms occur with longer duration of light exposure during the sensitive period (see Module 2, Regulation of Sleep for more information) rather than higher intensity of light.^2,3 White light at 2000 lux or less may be sufficient.²
• In the evening, about 2 hours before you need to go to sleep, use only dim light or wear dark sunglasses to prevent light from shifting the circadian rhythms to later bedtime and wake-up times, which is not what you want. Over the course of a few days, your body will shift its internal clock so that you begin to wake up earlier and get sleepy and ready for bed earlier in the evening.
• If you tend to wake up too early and get sleepy too early in the evening, your circadian rhythms may be shifted too early. For example, you are getting very sleepy at 8 p.m. and waking up at 4 a.m. but you prefer to get up later. To shift your circadian rhythms later, you can increase exposure to light in the evening and use dim light when you wake up in the morning. This promotes a later bedtime and a later wake-up time the next morning.
• Waking up too early can be caused by other factors: problems with the sleeping environment, too much caffeine, consuming alcohol close to bedtime, anxiety and worries, pain and other symptoms that disturb sleep. You can try correcting these. Make your sleep environment very dark, cool, quiet, and comfortable. End caffeine consumption earlier in the day and cut down on the amount. Avoid alcohol 2 to 3 hours before bedtime. Relaxation techniques (see at the end of this module) can reduce tension caused by stress and worries. See Module 4 for correcting symptoms from chronic diseases and medications that can disturb sleep.