Sleep apnea and asthma: how they overlap and why treating one can help the other

Sleep apnea and asthma overlap far more often than chance would explain. Studies find obstructive sleep apnea is more common in people with asthma, especially severe asthma, and people at high risk of sleep apnea are more likely to have asthma that isn't well controlled. The hopeful part is that in several studies, treating sleep apnea with CPAP was followed by better asthma control and quality of life. If your asthma keeps flaring at night despite your inhalers, sleep apnea is worth asking about.

How common is sleep apnea in people with asthma?

Sleep apnea is common in people with asthma. A 2017 meta-analysis in Scientific Reports pooled studies of adults with asthma and estimated that about 49.5% had obstructive sleep apnea. Adults with asthma had 2.64 times higher odds of sleep apnea than people without asthma. People with asthma and sleep apnea also tended to have a higher body mass index than those with asthma alone.

The more severe the asthma, the higher the rate seems to be. In a 2009 study in the Journal of Allergy and Clinical Immunology, researchers ran overnight home sleep studies on 26 people with severe asthma, 26 with moderate asthma and 26 people without asthma of similar age and weight. Using one scoring method with an AHI threshold of 15, sleep apnea was found in:

With a stricter scoring method, the rates were lower (50%, 23% and 12%), but the pattern was the same. Average oxygen levels overnight were also lower in the severe asthma group than in people without asthma. Among the people with asthma, though, the researchers found no significant correlation between how severe their sleep apnea was and measures of asthma severity or control. This was a small study, and the severe asthma group came from a difficult-asthma program, so the exact numbers won't apply to everyone with asthma.

Does asthma raise the risk of sleep apnea?

Asthma appears to raise the risk of developing sleep apnea. The best evidence comes from the Wisconsin Sleep Cohort Study, published in JAMA in 2015. Researchers followed 547 adults who didn't have sleep apnea at the start, testing them with overnight sleep studies every four years.

Over their first four-year follow-up, 27% of people with asthma developed sleep apnea, compared with 16% of those without asthma. After adjusting for sex, age, body mass index and other factors, asthma was linked to a 39% higher risk of new sleep apnea. Asthma was also linked to a higher risk of sleep apnea with habitual daytime sleepiness (relative risk 2.72). And the longer someone had had asthma, the higher their risk, rising by about 7% for every five years of asthma.

Why? A 2020 review in the American Journal of Respiratory and Critical Care Medicine points to airway and body-wide inflammation, interactions between nerves and the immune system, and the effects of asthma medicines, specifically corticosteroids, as factors that may predispose people with asthma to sleep apnea. That doesn't mean you should stop your steroid inhaler. Any change to asthma medicine should be made with your asthma team.

How does sleep apnea affect asthma control?

Sleep apnea seems to make asthma harder to control. In a 2010 study in Chest, 472 adults with asthma seen at a specialist clinic filled in questionnaires on sleep apnea risk and asthma control. Those at high risk of sleep apnea had 2.87 times higher odds of asthma that wasn't well controlled, even after the researchers accounted for obesity and other things known to worsen asthma. The authors recommended screening for sleep apnea in people who struggle to get their asthma under control.

The 2020 review describes the relationship as two-way, with each condition affecting the severity of the other. It says undiagnosed or poorly treated sleep apnea harms asthma control, partly because repeated drops in oxygen during the night drive airway inflammation and changes in the airway tissue.

This matters because nighttime is already a weak spot for asthma. The NHS says asthma symptoms may be worse at night and early in the morning. If you're waking with a cough, wheeze or tight chest, it's easy to put it all down to asthma, when sleep apnea may be part of the picture.

Other shared problems may tie the two together. Weight may be one, given the higher BMI seen in people with both conditions in the 2017 meta-analysis. Reflux may be another: in the CPAP study described below, reflux symptoms improved alongside asthma. We cover reflux in sleep apnea and acid reflux.

Does CPAP improve asthma?

CPAP has been followed by better asthma outcomes in several studies, though most weren't randomized trials. A prospective multicenter study, published in Allergy in 2017, followed 99 adults with asthma and moderate to severe sleep apnea for six months after starting CPAP. Over that time:

• the share with uncontrolled asthma fell from 41.4% to 17.2%
• the share who had asthma attacks fell from 35.4% to 17.2%, comparing the six months before and after starting CPAP
• asthma quality of life scores improved
• reflux and rhinitis symptoms, lung function on a reversibility test and a marker of airway inflammation also improved

Their asthma medicines and weight didn't change significantly, which makes it more likely that CPAP played a role. But there was no comparison group, so the improvement can't be pinned on CPAP with certainty.

A 2018 systematic review in Respiratory Medicine looked at 12 studies of people with asthma and sleep apnea treated with CPAP. It found a significant improvement in asthma quality of life scores but no significant change in lung function (FEV1). Results on asthma control questionnaires were mixed, improving in two studies but not in a third. Four studies reported better daytime or nighttime asthma symptoms, and three reported improved asthma severity. People used CPAP for an average of 19.5 weeks across the studies. The authors said the benefit seemed larger in people with severe sleep apnea or poorly controlled asthma.

CPAP is a treatment for sleep apnea, not for asthma. Keep taking your asthma medicines and following your action plan. Our guides to getting used to CPAP and whether CPAP is safe answer common worries, and sleep apnea treatment options covers alternatives such as oral appliances.

What about mouth tape if you have asthma?

Mouth tape isn't an asthma treatment or a sleep apnea treatment, and research on it in asthma is not encouraging. A 2009 randomized, single-blind crossover trial in Respiratory Medicine asked 51 adults with symptomatic asthma to tape their mouths at night for four weeks and breathe as usual for four weeks. Taping made no difference to morning peak flow, asthma symptom scores or any other measure. The authors concluded it had no effect on asthma control.

If you have asthma, talk to your doctor before trying mouth tape, and take it off straight away if you feel wheezy, tight-chested or short of breath. If you have sleep apnea as well, ask your sleep doctor first too. We cover this in detail in mouth tape and asthma. We don't recommend mouth tape for children.

What should you ask your doctor?

Bringing up sleep at your asthma review can be the simplest way in. The NHS says people with asthma should have check-ups at least once a year to see how well treatment is working. Useful questions include:

• Could sleep apnea be part of why my asthma is hard to control, given the 2010 study's recommendation to screen in that situation?
• Would a home sleep test or a lab study suit me better?
• If I start CPAP, how will we track whether my asthma changes?
• Should anything in my asthma action plan change at night?

When should you see a doctor?

See a doctor if your asthma is waking you up at night, your treatments aren't helping, or you need your reliever inhaler more often. Those are NHS reasons to see a GP. Ask about sleep apnea if you also snore loudly, someone has seen your breathing stop and start, you make gasping or choking noises, or you feel very tired in the day, which are NHS warning signs. A blocked nose that never clears is worth raising too. If you're pregnant, tell your clinician about any snoring or breathing pauses, and don't change asthma medicines without their advice.

Call 999 or your local emergency number if you're having an asthma attack and you feel worse at any time, you don't feel better after the maximum dose of your reliever inhaler, or you don't have an inhaler. That's the NHS's emergency advice.

Our guides to sleep apnea warning signs and the home sleep apnea test explain the next steps, and mild sleep apnea covers what a lower AHI means.

This article is general information, not medical advice. Talk to your doctor or asthma team about your own care.

Read next

• Mouth taping with asthma: what the research found
• Sleep apnea warning signs
• Sleep apnea and acid reflux

* This content is for informational and educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any disease or health condition. Talk to a qualified healthcare provider about your health.