Circadian Rhythm and Asthma

The correlation between the circadian rhythm and asthma is a complex issue involving many variables including genetic, hormonal and environmental factors.

After years of extensive research, the direct effects of circadian sleep cycles on the development and severity of asthma are becoming more transparent. Although the mechanisms are not clearly defined yet, researchers are hopeful that the new evidence will lead to better asthma management protocols and subsequently an improved quality of life for those with the condition.

Understanding Circadian Rhythm

The circadian rhythm is an approximate 24-hour cycle in the biochemical, physiological and behavioral processes of living beings. The word circadian comes from the Latin circa, meaning “around,” and diēm, meaning “day.” Circadian rhythms are endogenous cycles that occur naturally due to genetic and environmental influences and are responsible for regulating the body’s sleep-wake cycle. They are driven by the suprachiasmatic nucleus (SCN), a small region of the brain’s hypothalamus where all of these systems come together. The SCN receives information about light through our eyes, which allows it to coordinate daily functions like metabolism, body temperature, blood pressure, hormone release and more.

How Asthma Affects Lung Function

Nearly 300 million people worldwide suffer from asthma, a chronic disease that impairs lung function. It happens when the airways in the lungs narrow as a result of inflammation, making it difficult to breathe. Some people with asthma suffer from daily symptoms of wheezing, coughing, chest tightness or shortness of breath during what is known as an asthma attack or episode. The symptoms of asthma become exacerbated by exercise, inhaled allergens and other environmental factors. Symptoms also typically become worse at night, which in the past was mostly attributed to sleep position and other conditions within the sleeping environment. However, research studies now confirm a direct correlation between the circadian rhythm, the onset of asthma and nighttime asthma complications.

The Connection Between Circadian Rhythm and Asthma

In a 2020 BMJ Journal study, researchers found that night-shift workers had significantly higher rates of moderate to severe asthma compared to workers who worked daytime hours. People who worked irregular shifts that included periodic night-shift work were also at a greater risk for developing the disease. The study revealed disruptions in the body’s clock had a negative effect on lung function, causing inflammation and worsening symptoms for those who suffer from asthma.

Richard J. Martin, author of the research study Nocturnal Asthma: Circadian Rhythms and Therapeutic Interventions, notes that nocturnal asthma represents an exaggeration in the amplitude of regular circadian patterns, which includes an increase in the airway response with a decrease in lung function during the night and early morning hours: “Circadian changes in epinephrine, AMP, histamine and other inflammatory mediators, cortisol, vagal tone, body temperature, and lower airway secretions are potential mechanisms that favor nocturnal bronchoconstriction.”

People with asthma experience up to 50 percent less airflow than healthy individuals and are at risk for hypoxia, or low levels of oxygen in their blood, especially during sleep. The cumulative effects of low oxygen levels have detrimental effects throughout the entire body and can lead to cognitive decline, heart disease, diabetes and other health disorders. Low oxygen levels are also known to have a negative effect on mood and can increase anxiety and depression. Gaining a clearer understanding about the relationship between circadian rhythm and asthma may lead to not only better asthma treatment but also better health overall.