Biological rhythms are the natural cycle of change in our body’s chemicals or functions. It’s like an internal master “clock” that coordinates the other clocks in your body. The “clock” is located in the brain, right above the nerves where the eyes cross. It’s made up of thousands of nerve cells that help sync your body’s functions and activities.

There are four biological rhythms:

  • circadian rhythms: the 24-hour cycle that includes physiological and behavioral rhythms like sleeping
  • diurnal rhythms: the circadian rhythm synced with day and night
  • ultradian rhythms: biological rhythms with a shorter period and higher frequency than circadian rhythms
  • infradian rhythms: biological rhythms that last more than 24 hours, such as a menstrual cycle

The circadian clock plays a physical, mental, and behavioral role that responds to light and dark.

This clock helps regulate functions that include:

  • sleep schedule
  • appetite
  • body temperature
  • hormone levels
  • alertness
  • daily performance
  • blood pressure
  • reaction times

External factors can influence your biological rhythms. For instance, exposure to sunlight, drugs, and caffeine can affect sleep schedules.

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Disorders may develop when natural biological rhythms are disturbed. These disorders include:

  • sleep disorders: The body is “wired” to sleep at night. Disruptions in the body’s natural rhythms can lead to affected sleep, including insomnia.
  • jet lag: A disruption in circadian rhythms when traveling across time zones or overnight.
  • mood disorders: Lack of exposure to sunlight can lead to conditions like depression, bipolar disorder, and seasonal affective disorder (SAD).
  • shift work disorders: When a person works outside the typical work day it causes changes in typical circadian rhythms.

Biological rhythm disorders can affect a person’s health and feelings of well-being. Some of the effects include:

  • anxiety
  • daytime sleepiness
  • depression
  • lower performance at work
  • being more accident-prone
  • lack of mental alertness
  • increased risk for diabetes and obesity

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Some of the world’s most significant human errors have happened during night shift work. These include the Chernobyl disaster and the Three Mile Island accident. Also, most single-driver accidents occur in the time before dawn, according to Cornell University.

From a brain and body perspective, our bodies are made to sleep at night. This is why we don’t have adaptations like night vision and an enhanced sense of smell and hearing like nocturnal animals do.

An estimated 15 percent of full-time workers in the United States work shifts. Shift workers are usually in service-related jobs that are vital to the health and movement of society. They’re also more likely to sleep fewer than six hours a night.

Those who do shift work, or work outside the typical 9 a.m. to 5 p.m. workday schedule, are especially at risk for biological rhythm disorders. Examples of professions that involve shift work include:

  • healthcare workers
  • drivers, pilots, and others who provide transportation
  • food preparers and servers
  • police officers
  • firefighters

An NSF survey found that 63 percent of workers felt that their work allowed them to get enough sleep. The same survey also found 25 to 30 percent of shift workers have episodes of excessive sleepiness or insomnia.

Other groups of people who are at risk for a biological rhythm disorder include people who travel across time zones often or live in places that do not have as many hours of daylight, like Alaska.

Diagnosing biological rhythm disorders is usually a matter of a careful health history review. A doctor will ask you questions that may include:

  • When did you first notice your symptoms?
  • Are there activities that make your symptoms worse? Better?
  • How do your symptoms affect you?
  • What medications are you taking?

A doctor may also wish to rule out other conditions, like blood sugar disorders, that can cause similar mood disorder symptoms.

Treatments for biological rhythm disorders vary and depend on the underlying cause. For example, jet lag symptoms are usually temporary and don’t need medical treatment. In cases of shift work disorder or mood disorders, lifestyle changes may help.

Talk to your doctor about more serious symptoms, like fatigue, decreased mental sharpness, or depression. Your doctor will be able to prescribe the right treatment and provide lifestyle suggestions.

For people with seasonal affective disorder (SAD), a light box may help. These light boxes mimic daylight and can trigger the release of feel-good chemicals. These chemicals promote wakefulness in the body.

When lifestyle treatments and good sleep hygiene don’t work, your doctor may prescribe medication. Modafinil (Provigil) is for people who have difficulty with daytime wakefulness.

Your doctor can also prescribe sleep medicines as an option. But sleep medications should only be taken on a short-term basis. Sleeping pills can cause dependency and sleep-driving.

Understanding biological rhythm disorders can help you identify times when you may need to cope with energy dips and feelings of daytime sleepiness. Examples of steps you can take at home to combat changes in biological rhythms include:

  • Avoid substances known to affect sleep right before bed. These could include caffeine, alcohol, and nicotine.
  • Drink very cold drinks like iced tea or water.
  • Keep a regular sleep schedule whenever possible.
  • Take a brisk walk outside during daylight hours.
  • Take a brief 10 to 15 minute “power” nap.
  • Turn on more lights inside your home during the day. Conversely, turning the lights low or off at night can enhance sleepiness.

For night shifts, your body takes about three to four nights to adjust. Try to schedule your shifts in a row, if possible. This will reduce the amount of time to “train” your body for night shifts. But working more than four 12-hour night shifts in a row can have harmful effects, according to the Cleveland Clinic.

It’s important to remember that your biological rhythms are intended to protect you. They signal when it’s time to rest. And they assist you in the morning and early evening in being your most productive. You’ll get the most benefit in your day-to-day life when your biological rhythms are in sync.