Nocturnal asthma: What is it?

What is nocturnal asthma?

Like its name describes, nocturnal asthma (also called nighttime asthma) is the worsening of asthma symptoms at night. These symptoms, which often include cough, wheezing, shortness of breath, and chest tightness, may disrupt your sleep.

Nocturnal asthma is relatively common and occurs in all types of asthma, especially in cases of allergic, occupational, or exercise-induced asthma. One study published in the Journal of Asthma and examining 14,000 asthma patients estimated that 60% of patients with continuous asthma experience nocturnal asthma at some point.

What causes nocturnal asthma?

Doctors and the medical community are uncertain about what causes nighttime asthma, but a few of the following factors may be involved:

• Hormones: Many hormones in the body - including melatonin, cortisol and epinephrine, the hormones linked to the sleep cycle - follow a circadian rhythm, or a 24 hour cycle linked to the body’s internal clock. Changes in these hormones in the evening and while you sleep can impact the depth and rate of breathing, possibly contributing to asthma symptoms.
• Inflammation: As with hormones, steroid levels in the body decline naturally at night, leading to elevated inflammation and immune response, which can worsen asthma symptoms.
• Airway resistance: When we sleep, our airways become more narrow (called bronchoconstriction). In patients with asthma, narrowed airways is already an issue, so this slight change during sleep can exacerbate the problem.
• Muscle control: During sleep, our muscles relax, causing lowered muscle strength and control. Of course, breathing continues while we sleep, but the reduced muscle movement can lead to shallow breathing and smaller lung volume (the amount of air breathed in). This can be problematic for asthma patients in whom lung function is compromised.
• Sleep apnea: Sleep apnea is a condition where breathing is interrupted during sleep. When asthma and sleep apnea coincide, they can exacerbate each other.
• Allergens and late phase response: Exposure to allergens can trigger an asthma attack or can exacerbate symptoms, when the body’s response is delayed and occurs during sleep, this may lead to nocturnal asthma.
• Gastroesophageal reflux disease (GERD): GERD, also known as acid reflux, is a condition that is often linked to nocturnal asthma. Reflux of stomach acid through the esophagus to the larynx can trigger a bronchial spasm or can lead to airway constriction. Studies have found that up to 80% of people with asthma also have GERD symptoms, such as heartburn and regurgitation.

What are some of the complications of nocturnal asthma?

Besides the daytime drowsiness that interrupted sleep caused by nocturnal asthma may bring, it may also cause long-term health effects.

Over time, continued nocturnal asthma can worsen overall lung function and can cause asthma to progress. It also has been found to increase the risk of health problems such as heart disease and has been linked to increased risk of death. In fact, 80% of respiratory arrests (when breathing is stopped) and 70% of asthma-associated deaths occur during nighttime hours.

Though this may seem concerning, with your doctor’s help your asthma prevention and treatment plan can be fine tuned to better manage nocturnal asthma symptoms.

How is nocturnal asthma diagnosed?

If your asthma symptoms worsen significantly at night, your doctor may give you a separate diagnosis of nocturnal asthma in addition to your primary diagnosis (e.g. occupational asthma). 

In addition, a number of diagnostic tests can help to identify nighttime asthma. The challenge with diagnosing nocturnal asthma is that the symptoms may not be identifiable during the day, so you may be asked to take an at-home test or to do a sleep study:

At-home diagnostic test

This test will need to be done before going to sleep and in the morning right after waking so as to measure the impact of the nocturnal asthma on your lung function.

You will be asked to measure:

• Forced expiratory volume (FEV1): This is the amount of air you can exhale in one second with maximal effort. This can be done at home with a spirometer. In nocturnal asthma, the FEV1 value can decrease by at least 15% between bedtime and waking.
• Peak flow: This the total amount of air you can exhale and is not timed. Peak flow can be measured with a peak flow meter.In nocturnal asthma, this value will typically decrease by 15% or more between bedtime and waking. 

It is important to take note of the results and share them with your doctor. You may be asked to repeat each measurement a few times to avoid any possible error.

Sleep study

If your breathing at night is particularly impaired or if you are significantly fatigued during the day, your doctor may recommend a polysomnogram, also known as a sleep study.

A diagnostic sleep study occurs overnight and tracks your breathing rate, oxygen levels, muscle tone, sleep stages, and takes note of any gaps that may occur in your breathing overnight.

This may be performed at home with equipment you take home with you, or it may be done in a sleep lab.

How is nocturnal asthma treated?

Like with regular asthma, there is no cure for nocturnal asthma. Treatment is particularly focused on proper timing of daytime asthma treatments to help ease symptoms at night.

One of the key treatment methods for asthma is controller medications such as inhaled long-acting beta-agonist (LABA) bronchodilators, inhaled glucocorticoids, leukotrienes, and immunomodulators. These controller medications function by preventing symptoms, so they are not taken in emergency or when symptoms are already occurring. 

Your doctor will prescribe controller medications so that you have good asthma control in the moments when your symptoms are naturally worse - in the case of nighttime asthma, this moment is at night. It is important to follow your doctor’s instructions and take your medications when prescribed.

Nocturnal asthma can also be managed by treating any potentially contributing factors. Some techniques may include:

• Diet and lifestyle changes: Being overweight or obese are risk factors for both nocturnal asthma and GERD. Making healthy changes to your diet and getting adequate exercise can help to ease both conditions and can help to improve your sleep.
• Treating GERD: As mentioned previously, GERD can contribute to nocturnal asthma. Treating GERD specifically can help, especially by avoiding foods that are high in saturated fats or acids (fatty meats, fried foods, coffee, tea, spicy foods, citrus juices) and/or with use of over-the-counter medications like Prilosec or Tums. Make sure to consult your doctor before starting any new medication or diet.
• Quit smoking: Smoking has long been known to irritate the airways and aggravate asthma. A number of products are available to help you quit, such as nicotine gums, patches, or lozenges, many of which are covered by insurance.
• Eliminate allergens: Dust mites in your pillows or mattress can trigger an asthma attack, make sure to wash your bedding regularly and have your pets sleep outside your bedroom if you are allergic.
• Regulate the temperature of your sleeping environment: Depending on where you live and the time of year, the temperature can drop significantly during the night. To regulate the temperature, make sure your sleeping environment is well insulated, that the windows and any sources of drafts are closed, and try using a humidifier to increase humidity if the air is dry.
• Reduce psychological stress: Stress can contribute to asthma attacks, so working with a mental health professional and/or utilizing relaxation techniques like meditation, deep-breathing, yoga, or even journal writing can help reduce stress. If you have a clinical condition like depression or anxiety, certain medication may help.

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