Bimodal Circadian Rhythm (BCR) : Apollo Health

Bimodal Circadian Rhythm is also commonly referred to as an irregular sleep/wake cycle. While a normal circadian rhythm (daily activity cycle) runs through one sleep/wake cycle in 24 hours, a bimodal circadian rhythm tends to disrupt that cycle. BCR creates more than one low or sleep period, but the sleep periods may not be pronounced enough to allow sleep. Those with BCR tend to sleep for only a few hours each night, generally from about 2 am - 6 am or earlier. BCR may be one of the most common of circadian rhythm problems among the elderly or indigent who do not receive consistent light/dark signals.

BCR Symptoms

You may experience one or more of the following symptoms:

Early morning sleeplessness, lack of energy during the day, feeling tired in the mid day, early afternoon and/or evening.

Difficulty falling asleep, an inability of staying asleep, and awaken one or more times during the night.

Alertness and ability to function may also be diminished.

How BCR Affects You

Because your daily cycle, or circadian rhythm is not operating properly, your pineal gland may be releasing the night time hormone melatonin during your day cycle, causing you to feel tired in the at various times during the day. Since melatonin is released prematurely, your body clock can't sustain a complete sleep cycle. You may experience a disrupted sleep and awaken early. You may also have difficulty falling asleep. Because you don't receive the proper amount of sleep, your energy, alertness and ability to function may also be diminished.

Treatment Recommendations for BCR

Specialized bright light (10,000 lux intensity) may be an effective treatment for BCR. Since bright light will suppress melatonin for approximately three hours, you should use bright light in the mid morning, afternoon, late afternoon and evening while avoiding bright morning light before 9:00 am. If you need to be outside or in bright light before this time, you should wear sunglasses.

Since BCR may cause you to be awake during the night, it is important to avoid light during the night. Even low levels of light such as a nightlight, can produce enough of a signal to adversely affect your circadian rhythm and prolong the BCR. Watching TV is acceptable, if no other lights are on, and you stay at least 8 feet from the TV. If you feel this is too restrictive, try using a lamp with a 20-watt or lower wattage bulb.

Nighttime Instructions

During the first ten days of shifting your circadian rhythm back to a normal pattern, you may benefit from taking time-release melatonin approximately two to three hours before your bedtime. Also, try to make your night time as dark as possible, and avoid using light when getting up during the night.

Alternative Treatment Instructions

Since BCR or irregular sleep/wake cycles have severely disrupted circadian rhythms, it may be easier to use a new therapy to completely reset your circadian rhythm. Sleep Restriction retrains the body clock to allow sleep only during one cycle in the day. Sleep restriction involves bright light therapy and requires from 3 - 4 weeks to work, but those who have tried sleep restriction find their sleep improves at least 2 - 3 hours per night. For more information, see the section on sleep restriction in this web site.