Why Is Asthma Worse at Night?
In 1698, British wrote physician John Floyer an asthma deal, the first principal work to focus on disease. Not all of them are old. He warns that those who are sad or angry are more likely to experience attacks, because grief stops the “Movement of Laughter.” He also recommends some treatments including regular, mild vomiting.
In an asthma attack, the airways in a person’s lungs begin to close, so they have difficulty breathing and cause chest tightness, coughing, and sneezing. But Floyer’s piece also notes a common symptom: His own asthma is almost always worse at night, sometimes waking him up at 1 or 2 in the morning. Hundreds of years ago, scientists found evidence to support him: A study from 2005 showed that almost 75 percent in people with asthma experience more severe attacks at night. A famous survey of mortality in London hospitals in 1970 showed early morning and evening attacks. likely to be fatal.
Although it’s not sure why asthma gets worse at night, said Steven Shea, director of the Oregon Institute of Occupational Health Science at Oregon Health and Science University. “Most people sleep at night, so maybe sleep is causing your asthma to get worse at night,” he says. Or it can be caused by body position or mites or bedtime allergies. Or, Shea added, “maybe it’s the body’s internal clock.”
That body clock is also called the circadian system. Among other vital functions, it controls hormones, heart rate, and the immune system in a cycle that lasts about 24 hours. While this system is indoor, it is heavily influenced by external factors such as light and dark, meal times, and work schedule.
Historically, it has been impossible to separate the role of the circadian system from human behavior and environmental hazards “because they are the same,” said Frank Scheer, director of the Medical Chronobiology Program at Brigham and Women’s Hospital. “You never know what’s really driving the changes in pulmonary function.” But in a role published this month on Methods of the National Academy of Science, a team led by Scheer and Shea finally found a way to separate the circadian system from all the external factors that could contribute to asthma.
First, they had 17 study participants, all of whom had previously been diagnosed with asthma, monitoring their pulmonary function at home in their daily lives. Four times a day, participants used a handheld spirometer to test how much air they could expel from their lungs in a second, a resistance called FEV1. (The more, the better.) They also record their symptoms and note when they should use their rescue inhalers.
After all, things get more involved. The same set of participants were placed in two different experiments while living in unoccupied rooms at the Center for Critical Inquiry at Brigham and Women’s Hospital. In one experiment, called the “regular routine protocol,” participants sat in bed for 38 hours without being allowed to fall asleep. They cannot get up to use the bathroom or do any strenuous activity. Every two hours, they eat the same snack, a little peanut butter and jelly or tuna fish sandwich. They were allowed to listen to tape books, talk to nurses, or play card games, but they could not move or get excited or angry.
In these rooms with no clocks or windows, and with subjects no longer tied to their daily work or home schedule, the time outside seems to be without it. Participants did not know when the sun would rise or set, when it would be time for lunch, or when they should go to bed.