Newest Research Links Asthma to Circadian Rhythms

All living things possess a body “rhythm” that coordinates in some way with the planet’s light-dark cycles.

For humans, it’s the circadian rhythm, a deep internal process tied to organ function, and a host of other processes that most famously include our sleep-wake cycles. When we experience circadian dysfunction of any kind, it can be disruptive to our overall health. This disruption can be temporary (such as with jet lag) or it can be ongoing. When it becomes an ongoing problem, risks increase for developing chronic illness or seeing a worsening of the conditions we already live with.¹

About 25 million people live with asthma in the United States. Clinically significant insomnia is experienced by 37 percent of these people. Between 30 and 50 percent of people with asthma experience excessive daytime sleepiness (EDS) due to sleep disruptions.^2,3,4

Just having asthma, by itself, can lead to problems with falling and staying asleep. When circadian rhythms fall out of balance in people with asthma, this brings additional cause for concern. Recent research seems to bear this out.

A closer look at nocturnal asthma

It has been long-recognized that asthma severity is linked to our circadian rhythms. Typically, the worst symptoms occur at night, leading to the common term, nocturnal asthma, to reflect this reality. It is thought that as many as three out of four people with asthma experience nocturnal worsening of asthma symptoms.

What has not been well understood are the factors that lead to asthma severity at night. Everyday behaviors might be to blame, like exercising and sleeping. However, the environment can also play a role. Air temperature and pollution are two major factors you might recognize.

But there’s a third target — the circadian system — which might also shape the nature of a case of asthma.

New research targets the circadian “body clock”

A comprehensive long-term study of asthma patients published in September 2021 tested the idea that our circadian rhythms might independently contribute to worsening asthma during sleep. They studied people with asthma for three weeks in a setting that included behavioral, environmental, and circadian influences. A series of protocols helped them to better identify which of these influences could be blamed for periods of nocturnal asthma. During protocols, steroid use was curbed, sleep-wake cycles were manipulated, and snacks and body posture were adjusted.⁵

The researchers found that disrupted circadian rhythms influenced pulmonary function independently of everyday behaviors and environmental factors. “Laboratory protocols revealed significant circadian rhythms...uncovering a nocturnal exacerbation of asthma usually unnoticed or hidden by the presence of sleep,” the authors of the study noted. The worst cases of asthma — especially related to airway resistance and forced expired volume (FEV1)—were traced to periods of lowest pulmonary function occurring around 4 a.m.

The scientists also discovered that the use of rescue bronchodilators for symptoms occurred four times as often during the night, confirming that problems of nocturnal asthma are disruptive of sleep. Regularly interrupted, nonconsolidated sleep is a hallmark of circadian rhythm dysfunction.

"Only by using circadian protocols that scheduled wakefulness across the night was it possible to uncover the severity of nocturnal worsening of asthma, whereas this worsening could be masked by sleep (and lack of measurements during sleep) in the normal daily routine,” the researchers concluded.

Timing matters

It is scary to consider that the highest rates of nocturnal asthma symptoms leading to respiratory failure or death occur mostly at night while we are trying to sleep. For this reason, pulmonologists urge their asthma patients to tend to their symptoms at all times of the day, with an eye toward preventing problems of inflammation, constricted airways, and chest tightness that can occur at night.⁵

Because of the findings of this latest research, treatment options may be refined to include timing. Such therapies are referred to as chronotherapy. For instance, therapies that target the circadian system might use timed light exposure or timed medications to treat nocturnal asthma, reduce side effects of medications, or influence the function of the circadian “body clock” itself.

This latest research suggests that “it seems that any chronotherapy that targets the circadian system or factors that have endogenous circadian rhythmicity ought to consider a patient’s endogenous circadian phase.” ⁵

What’s next for people with asthma?

The next time you go to see your pulmonologist, you may wish to discuss your sleep health.

This should include information about your sleep-wake cycles, frequency of nocturnal asthma events, an account of regular activities (such as going to the gym or jogging), your medication list, and any other sleep disorders (especially sleep apnea).

What insights your physician can glean from this personalized information may lead to a new pathway forward, to an emerging practice now referred to as “circadian precision medicine.” ⁵