| Circadian rhythms are changes in body functions, such as temperature regulation and sleep cycles, which occur during a 24-hour period. People with circadian rhythm disorders may have insomnia and daytime sleepiness because their circadian rhythms follow an abnormal pattern. |
| Shift work sleep disorder — People who work late night shifts can have difficulty sleeping during the daytime. This is especially true for people who work rotating or permanent night shifts, who often revert to sleeping at night on days off in order to spend more time with their family. Treatment often includes adopting a consistent daily sleep routine seven days per week. |
| Delayed sleep phase syndrome — Some people have a sleep-wake rhythm that is shifted later in the day. These people want to go to bed at a later time and sleep later in the morning. However, this is usually not practical because of school or work requirements. This problem is common in young adults, who typically have a sleep-wake rhythm that is longer than 24 hours and pushes them to stay awake longer. Treatment usually includes trying to wake at an earlier consistent time each day, exposure to bright light on awakening, reducing stimulating activities in the evening, and avoiding electronic devices that give off light (such as smartphones and tablets) in the evening. |
| Advanced sleep phase syndrome — Going to sleep in the early evening and waking earlier than desired is common in middle age and older adults. Attempts to stay up later may not allow the person to wake later in the morning. Increased activity and exposure to bright light in the evening can help adjust the rhythm to allow later bedtime and wake time. |
