Nocturnal (Nighttime) Asthma: Symptoms, Causes, Treatment, Prevention
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If you have asthma and wake up coughing and wheezing at night, you may have a condition called nocturnal asthma, or nighttime asthma.
Just as with daytime asthma, nocturnal asthma can vary from mild to severe. But when asthma symptoms come on at night, the health impact is amplified: The fits of coughing and chest tightening may lead to sleep deficiency, which is associated with a higher risk of chronic conditions such as heart disease, diabetes, and depression.
Keep reading to find out what you need to know about the symptoms, risk factors, and treatment of nocturnal asthma so you don’t find yourself coughing and wheezing in the middle of the night.
How Common Is Nighttime Asthma?
Nocturnal asthma is surprisingly common, says Diana Chen, MD, clinical assistant professor and pulmonologist at Stanford Medicine in California. “About 30 to 70 percent of patients with asthma will report nocturnal symptoms at least once a month,” she says.
“If people are having nighttime symptoms that are more than once or twice a week, we will want to keep an eye on them to make sure their asthma is being appropriately managed,” Dr. Chen says.
Symptoms of Nocturnal Asthma
Symptoms of nocturnal asthma are similar to those of daytime asthma, according to the Asthma and Allergy Foundation of America. “Patients will report coughing, wheezing, shortness of breath, and chest tightness. These are often the same symptoms that can occur during the day,” says Chen.
The frequency and severity of nocturnal symptoms usually correspond with daytime symptoms: If they are mild during the day, for instance, they tend to be mild at night, Chen says. “A key difference is that with daytime symptoms, people can often carry on with their day, but when that occurs at night it can disrupt their sleep,” adds Chen.
Children can also have nocturnal asthma, and in those cases it’s not just the kids whose sleep is negatively impacted: The parents or caregivers end up with poor sleep, too, she adds.
What Causes Nocturnal Asthma?
Some people may have worsening symptoms at night because asthma is associated with a circadian pattern — an internal clock — in their lung function, explains Chen.
Although the central circadian clock is located in the brain, scientists have established that the body has multiple internal clocks that are calibrated in different ways, according to a report published in the journal Cell. Nearly every cell and tissue in the body, including the lungs, has its own pattern that not only syncs up with other cells that perform the same function, but also with other systems in the body.
“The best lung function typically occurs around four in the afternoon and then it’s worse at four in the morning. So, you can imagine that’s why some patients may have worsening symptoms in the middle of the night,” says Chen.
Hormones Can Also Affect Nocturnal Asthma
Because of the circadian pattern, everyone — even people who don’t have asthma — experiences a drop in lung function at nighttime. “It’s not a huge drop; there’s maybe about 5 to 8 percent difference between the low points of function at night compared to the daytime peak,” Chen says.
But in patients with nocturnal asthma, the variation is much larger, with about a 15 to 50 percent difference. “So, nocturnal asthma seems to be sort of just an exaggeration of these normal changes that we see,” says Chen.
The hormones our body releases at different times of the day also influence nighttime asthma symptoms. For example, the body releases the “stress hormone” cortisol at different levels throughout the day, with the lowest point usually around midnight, Chen says. That may contribute to the difficulties of those with nocturnal asthma.
Why? Cortisol is a so-called steroid hormone that helps inhibit the inflammatory process that can cause asthma symptoms, says Jill Poole, MD, professor and division chief of allergy and asthma at Nebraska Medicine in Omaha, and an expert for the Allergy and Asthma Foundation of America. “Inhaled steroids are used as an asthma treatment for the same reason: to calm the inflammatory process and hyper-responsive airways,” Dr. Poole says.
Who Is at Highest Risk for Nocturnal Asthma?
People who have poorly managed asthma are at the highest risk for experiencing nighttime symptoms, says Chen. “It could be that the dose of their current medication is not enough or maybe they have a coexisting diagnosis that contributes to having challenges in controlling their asthma — for example, if they have concurrent rhinitis [runny nose and congestion], sinus issues, or reflux,” she says.
There are also racial and ethnic factors. In a study published in the American Journal of Respiratory Critical Care Medicine, African American people were more than twice as likely to report nocturnal asthma compared with European Americans.
“Maybe there’s some genetic variants that influence the circadian rhythm of lung function and contribute to the likelihood of nocturnal asthma,” says Chen.
Family history, allergies, viral respiratory infections, occupational exposures, smoking, air pollution, and obesity are all associated with an increased risk of having asthma in general, according to the American Lung Association.
The Link Between Nocturnal Asthma and Sleep Apnea
Obstructive sleep apnea (OSA), a condition that involves multiple interruptions in breathing throughout the night, may mimic nocturnal asthma or occur along with the condition.
OSA involves both hypopneas (periods when breathing is reduced, limiting intake of oxygen) and apneas (periods when breathing completely stops, typically because body parts like the tongue or throat muscles are blocking the upper airway).
People with asthma appear to have an increased risk for OSA compared with the general population, according to a study published in March 2019 in the American Journal of Respiratory and Critical Care Medicine. At the same time, undiagnosed or uncontrolled OSA can make nighttime asthma worse, according to the authors.
“For those who have a diagnosis of nocturnal asthma and sleep apnea, getting treated for sleep apnea is highly beneficial,” says Poole.
Exactly what leads to that improvement isn’t known, but it’s suspected that the use of a CPAP machine (continuous positive airway pressure, a common treatment for sleep apnea) may eliminate any irritation in their throat and voice box that can lead to sleep interruption. “The irritation there can cause this reflex bronchoconstriction, meaning the airways start to close off. If you treat the sleep apnea and get rid of the irritations, your airways don’t close off,” says Chen.
Another theory is that sleep apnea treatment improves oxygen saturation (a measure of oxygen levels in the blood), Chen says. Nighttime asthma is associated with low oxygen saturation, according to a study published in October 2022 in the Journal of Clinical Sleep Medicine.
But unless a person with nocturnal asthma also has obstructive sleep apnea, a CPAP machine won’t help. “If you treat a person with asthma without sleep apnea with a CPAP, it doesn’t have any effect on their symptoms,” says Chen.
Expert Tips for Managing Nocturnal Asthma
If you’re frequently experiencing nocturnal asthma symptoms, it’s important to figure out the root of the problem. Chen say to consider the following:
- Medication Timing Most asthma medications are taken twice a day, in the morning and evening. “Adherence is important; make sure you’re not skipping your afternoon-evening dose. You also might talk with your doctor about changing the timing of your second dose to see if that helps,” says Chen.
- Proper Inhaler Use When patients tell her they’re experiencing nocturnal asthma, Chen checks to make sure they’re using correct inhaler technique and refilling their medications on time. Most inhalers have a little dose counter on the back to tell you how many puffs are left, but some patients aren’t clear on what that means, says Chen. “Even when it reads zero, when they push down, there’s still something that comes out, and so they assume there are still doses left. They don’t realize that it’s the propellant and not actually medication,” she says.
- Triggers There are also external factors that make nighttime symptoms worse and include the “usual suspects” that also trigger daytime asthma. “These include things like pets, pollen, mold, and smoke — so eliminating those or finding ways to minimize their effect may help,” says Chen.
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