Why does asthma get worse at night?

In 1698, England Dr. John Floyll wrote Asthma Monograph, The first major work focused on disease. Not all are aging. He warned that those who are sad or angry are more vulnerable to attacks because sadness prevents “humorous movements.” He also recommended some treatments, including regular, mild vomiting.

During an asthma attack, the air passages in a person’s lungs begin to close, making it difficult for them to breathe and causing chest tightness, coughing, and wheezing. But Freud’s article also pointed out another important symptom: his own asthma is almost always worse at night, sometimes waking him up at 1 or 2 in the morning.Hundreds of years later, scientists found evidence to support him: a study in 2005 showed that almost 75% Of asthma patients have more severe attacks at night. A well-known London hospital mortality survey in the 1970s showed that early morning and night attacks were More likely to be fatal.

However, Steven Shea, director of the Oregon Institute of Occupational Health Sciences at Oregon Health and Science University, said that no one is sure why asthma gets worse at night. “Most people sleep at night, so maybe sleep makes your asthma worse at night,” he said. Or it may be caused by mites or allergens in body posture or bedding. Or, Shea adds, “Maybe it’s the body clock.”

This biological clock is also called the circadian rhythm system. Among other important functions, it regulates hormones, heartbeat, and immune system in a cycle that lasts about 24 hours.Although this system is internal, it is severely affected by external factors such as light and shade, meal times, and work schedule.

Historically, it has not been possible to isolate the role of the circadian system from people’s behavior and environmental risks, “because they complement each other,” said Frank Scheer, director of the Medical Time Biology Program at Brigham and Women’s Hospital. “You can’t know what drives the changes in lung function.” But in a dissertation Published this month Proceedings of the National Academy of Sciences, The team led by Scheer and Shea finally found a way to separate the circadian rhythm system from all external factors that may cause asthma.

First, they asked 17 study participants to track their lung function at home in their daily lives, all of whom were previously diagnosed with asthma. Participants used a handheld spirometer four times a day to test how much air they could expel from their lungs in one second. This measurement is called FEV1. (The more the better.) They also recorded their symptoms and recorded when they must use a rescue inhaler.

Then, things became more complicated. The same group of participants underwent two different experiments while living in a dimly lit room at the Critical Care Investigation Center of Brigham and Women’s Hospital. In an experiment called “Constant Routine Protocol,” participants sat in bed for 38 hours and were not allowed to sleep. They cannot get up to go to the bathroom or do any strenuous activities. Every two hours, they eat the same snack, a small piece of peanut butter and jelly or tuna sandwich. They are allowed to listen to books on tapes, chat with nurses, or play card games, but they cannot walk around, nor are they excited or angry.

In these rooms without clocks or windows, the subjects are no longer bound by their daily work or family schedules, as if external time does not exist. Participants did not know when the sun would rise or set, when to eat lunch, or when they should fall asleep.