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Getting Into a Rhythm: Circadian Rhythms and How They Affect the Body

While the future of daylight saving time is being considered federally and in some states, Coloradans will be setting clocks back by one hour this weekend, a ritual that could affect circadian rhythms. The minor shift in time affects a person’s exposure to light, a critical factor in maintaining a healthy sleep/wake cycle. 

The term “circadian rhythm'' describes the physical, mental and behavioral changes that follow a 24-hour cycle in most living things, including humans. Simply put, circadian rhythms are part of the body’s internal clock that tells people when to sleep and when to be awake. 

When a woman says her biological clock is ticking, it really is. Both women and men have an internal master clock, which is sometimes referred to as the “circadian pacemaker.” Composed of about 20,000 nerve cells that form a structure in the brain called the suprachiasmatic nucleus (SCN), the master clock sends signals to regulate activities throughout the body, including sleep/wake cycles, eating habits and digestion, as well as body temperature. The SCN is highly sensitive to light, sending signals that bodies should be awake when light is present and should be asleep when it’s dark. 

Dr. Surit Sharma is a board-certified pulmonologist and sleep medicine specialist, who performs sleep disorder evaluations at Vail Health’s Sleep Disorder Center. He explained that there are “zeitgebers” or environmental cues that help synchronize the body’s rhythms. 

“Light,” he said, “is the strongest zeitgeber in regards to sleep cycles.” 

When it’s dark out, a biological process in our bodies helps produce melatonin, a hormone that influences sleep. Production of melatonin slows in the morning when exposed to light, causing humans to wake up and feel alert. Research has shown that daylight saving time transitions can cause circadian misalignment, which can contribute to sleep loss. Some people adjust quickly, while others can suffer from sleep debt, a cumulative effect of not getting enough sleep on a regular basis. 

People who are blind can struggle with sleep because their eyes cannot transmit as many light signals to their brains, causing disruptions to their internal clock. According to the National Sleep Foundation, “between 50% and 80% of blind people report sleep disturbances, and experts estimate half of totally blind people have non-24-hour sleep-wake rhythm disorder.”

For those whose internal clocks are properly aligned with the day-night cycle, circadian rhythm can promote consistent and restorative sleep. Circadian rhythms vary from person to person, and they tend to be similar among family members. The pattern in which people sleep and wake is called “chronotype,” and it refers to a personal circadian rhythm. Most people fall into one of two chronotypes–the morning person and the night owl. Annoying to those who need a cup of coffee before anything else, morning people find it easy to wake up and have the most energy during the day. Some research suggests that the body clock in a morning person runs faster than 24 hours. Night owls, on the other hand, might have a body clock that runs slower than 24 hours. These people find it hard to wake up in the mornings and have the most energy later in the evening. 

Circadian rhythms can change. The body clock shifts naturally during adolescence, for example. Those with teenagers may notice they go to bed later and sleep in more than they did as kids. That works out fine on most weekends and in the summer, but most schools start at around 8 AM. Fortunately, circadian rhythms can be adjusted, but it’s a process that should be rolled out slowly and consistently; otherwise, parents could suffer a crankier teen than usual. Sleep specialists recommend interventions like melatonin at night and exposure to light in the morning. 

“Waking up 15 minutes earlier each morning over the course of a week can also help the body to slowly acclimate,” said Dr. Sharma. “If you have to pick one area to work on, it’s your wake-up time. Once you achieve your goal, you want to keep that schedule seven days/week. It’s consistency that’s most important, and that can be difficult for people.”

Dr. Sharma suggested that as long as someone’s sleep/wake cycle isn’t affecting their work or personal life, it’s not worth changing as long as they’re getting sufficient rest. 

“I have some patients who are retired,” said Dr. Sharma. “They know when they like to sleep and when they like to wake up. When they’re awake, they have energy and are functioning well. Those aren’t the patients I worry about. It’s the patients who are totally desynchronized with the rest of their life–and it’s creating problems with their employment, school, their social interactions. They’re stressed about it, and that’s a problem.”

Patterns of sleeplessness are frustrating and can affect a person’s health. 

“We know definitively that there’s a correlation between sleep deprivation and decreased higher cognitive function and increased metabolic syndromes. Individuals who are chronically sleep-deprived have a higher tendency to have issues related to heart disease, glucose control and obesity,” said Dr. Sharma. 

Insomnia is the most common sleep disorder, but people of all ages can suffer from circadian rhythm-related sleep disorders, a group of conditions tied to dysfunctions or misalignments with the body’s internal clock. Those having trouble falling asleep until late in the night could be struggling with a delayed sleep phase disorder, making it hard to wake up in the morning. Others are ready for bed shortly after dinner, finding themselves waking up at around 2 a.m.–this is known as an advanced sleep phase disorder. Other disorders are the result of a mismatch of the body’s natural body clock and external factors like traveling to a different time zone (jet lag), working a night shift or poor sleep habits. 

Because sleep is so critical to good health, Dr. Sharma recommended speaking with a primary care provider if you or a loved one are experiencing insomnia, sleep loss or difficulty waking up. If sleep studies are recommended, they can be performed at Vail Health or even at home. 

“Home sleep testing requires less monitoring, which means it can miss certain subtleties, but it’s less expensive, less hassle for the patient and it’s much easier to sleep at home than in a lab,” said Dr. Sharma. 

Good sleep habits, sometimes referred to as “sleep hygiene” can promote a healthy rest, and therefore, a healthy body. As the time change approaches this Sunday, start preparing now by going to sleep a little later each night. Get outside in the sunlight during the day, and if you experience sleep loss at night, try a short power nap of under 20 minutes. Establish healthy sleep habits, and if you have concerns, talk to your primary care provider or try some of the tips below.