![]() “This identifies new pathways that might suggest new ways to treat asthma,” Ray says. That answers a big, basic question and allows the field to move forward toward possible therapies. “They were able to really clearly show that it’s the endogenous circadian system driving this,” he says. Very few labs in the world have the ability to run experiments like this, says David Ray, a professor of endocrinology at Oxford University who studies the circadian system but was not involved in this study. “The circadian clock is ticking away all of the time, but we’re doing things all of the time as well, and you really need to know how they add up,” he says. It’s always going to be affected by light, sleep cycles, mealtimes, exercise, and work. But he also adds that behaviors can still affect the severity and frequency of attacks-because unless you’re in a highly controlled lab environment, the circadian clock is never working alone. Shea says these sophisticated protocols allowed them to finally conclude that circadian rhythms do affect asthma, independent of other behavior, no matter whether people are asleep or awake. ![]() The researchers also found that when sleep coincided with the circadian night, airway resistance increased. Participants who had the most pronounced increases in lung function during their circadian day also had the greatest drop in FEV1 and the greatest increase in airway resistance during their circadian night. During the circadian night, when people’s internal clocks perceived it was time to sleep, participants were four times more likely to use their inhalers. Every two to four hours, they were also tested for airway resistance and FEV1.Īcross all three experiments, the researchers found that a person’s circadian rhythm contributes to worsening asthma. They were allowed to get up and move around a bit more than in the constant routine protocol, but they couldn’t go outside or do any strenuous exercise. ![]() This forced their behaviors out of sync with their circadian rhythms, “meaning that you will be able to dissociate the influence of the behavioral cycle from the central circadian control,” says Scheer. Instead of living on a 24-hour cycle, all their activities-like sleeping, showering, and eating-were scheduled on a 28-hour cycle. So they ran another phase of the experiment called the “forced desynchrony protocol.” This time, the 17 participants had to live in those dim light conditions for eight days. This gave the researchers a way to follow along as the circadian rhythm regulated the rise and fall of hormone levels and pulmonary function-without influence from behavioral or environmental cues.īut they also wanted to understand how behavioral cycles like sleeping or eating might affect asthma, too. Every two to four hours, nurses collected blood and urine samples, took FEV1 metrics, and also measured airway resistance, which indicates if swelling or mucus buildup are making it harder to move air through the lungs. Participants were hooked up to thermometers that monitored their core temperatures almost continuously. “The constant routine protocol is based on the concept that you remove any 24-hour rhythmicity and any factors, environmental or behavioral, that may induce changes in physiology,” says Scheer. Or, Shea adds, “maybe it’s the internal body clock.” Or it may be caused by body position or mites or allergens in the bedding. "Most people sleep at night, so maybe it’s the sleep that causes your asthma to get worse at night," he says. ![]() Yet no one is sure why asthma gets worse at night, says Steven Shea, director of the Oregon Institute of Occupational Health Sciences at Oregon Health and Science University. A famous mortality survey of London hospitals in the 1970s showed that early morning and nighttime attacks were more likely to be fatal. Hundreds of years later, scientists were finding evidence that backed him up: A study from 2005 showed that nearly 75 percent of people with asthma experience worse attacks at night. But Floyer’s piece also noted another important symptom: His own asthma was almost always more severe at night, sometimes waking him up at 1 or 2 in the morning. In an asthma attack, the air passageways in a person’s lungs start to close, making it hard for them to breathe and causing tightness in the chest, coughing, and wheezing. He warned that those who were sad or angry were more likely to experience attacks, as sadness would stop the “Motion of Humors.” He also recommended a few cures including regular, gentle vomiting. In 1698, British doctor John Floyer wrote a treatise on asthma, the first major work focused on the disease.
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