TECHNOLOGY

Why is asthma worse at night?


In 1698, the British Dr. John Flower wrote a book on asthma, the first major work on this disease. Not all of them are of good age. He warned that those who are sad or angry are more likely to be attacked, as sadness will stop the “movement of humor”. He recommended several cures, including regular, mild vomiting.

In an asthma attack, a person’s lungs begin to stop ventilating, causing them to have difficulty breathing and stiffness in the chest, coughing and shortness of breath. But Flour’s piece also noticed another important symptom: his own asthma was almost always more intense at night, sometimes waking him up at 1 or 2 in the morning. Hundreds of years later, scientists were finding evidence to back it up: a 2005 study found that about 5 percent of people with asthma had a bad attack at night. A well-known death survey of London’s hospitals in the 1970s showed that morning and night attacks were more likely to be fatal.

Still, no one is sure why asthma gets worse at night, said Steven Shea, director of the Oregon Institute of Occupational Health Sciences at the University of Oregon Health and Science. “Most people sleep at night, so maybe your asthma gets worse at night because of sleep,” he said. Or it may be due to body position or bed bugs or allergens. Or, Shia added, “perhaps it’s the body’s internal clock.”

That body clock is also called the circadian system. Among other important functions, it regulates hormones, heartbeat and immune system on a cycle that lasts about 24 hours. Although this system is internal, it is greatly influenced by external factors such as light and dark, meal times and work schedules.

Ig Historically, it is impossible to separate the role of circadian systems from human behavior and environmental risks “because they go together,” says Frank Shearer, director of the medical chronobiology program at Brigham and Women’s Hospital. “You may not know what is actually changing in pulmonary function.” But in a study published this month Proceedings of the National Academy of Sciences, A team led by Shear and Shear has finally found a way to isolate the circadian system from all external causes that could contribute to asthma.

First, they had 17 study participants, all of whom had previously been diagnosed with asthma, who tracked pulmonary function at home in their daily lives. Four times a day, participants used a handheld spirometer to test how much air they could get out of their lungs in one second, a measure called FEV1. (The more, the better.) They also record their symptoms and notice when to use their rescue inhalers.

After that, things got significantly more involved. The same participants were put through two different tests while in dimly lit rooms at the Center for Critical Inquiry at Brigham and Women’s Hospital. In one experiment, called the “constant routine protocol,” participants sat in bed for 38 hours without permission to sleep. They cannot use the bathroom or do any strenuous activity. Every two hours, they ate the same snack, a small peanut butter and jelly or tuna fish sandwich. They were allowed to listen to books on tapes, chat with nurses or play cards, but they could not move around or get excited or angry.

In these rooms without clocks or windows, and because subjects were no longer tied to their daily work or home schedule, external time seemed to exist. Participants had no idea when the sun would rise or set, when it might be lunch time, or when they should fall asleep.



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