Symptoms and Treatment of Nocturnal Asthma

Woman sleeping in bed
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If you have nocturnal asthma, your forced expiratory volume (FEV1) decreases by at least 15 percent from bedtime to getting up in the morning. For some, the decline in lung function can be significantly more. This is associated with increased symptoms, such as cough, wheezing, and shortness of breath that disrupt sleep.

Risks of Nocturnal Asthma

Patients with large nighttime changes in their FEV1 may also have more daytime symptoms and poorer asthma control.

Another concerning fact is that nocturnal asthma may be related to asthma mortality. Seventy percent of deaths and 80 percent of respiratory arrests caused by asthma occur during nocturnal hours. A large variation in peak expiratory flow is not correlated with asthma severity but is an independent risk factor for respiratory arrest. Most patients understand that more severe symptoms are associated with increased risk of death, but very few people are aware of large variations in nocturnal peak expiratory flows being a risk factor for poor outcomes.

Causes

It is not known whether the decline in lung function is due to circadian rhythm changes (changes in lung function due to a biological like clock) or whether they are somehow related to sleep itself. Not all asthma patients, however, experience problems at night.

There are some physiologic changes that occur during sleep that may help explain why some asthma patients experience problems.

Resistance tends to increase at night and lung function decreases as sleep time increases. This last fact is true in patients without asthma, but not to the point where they develop symptoms.

Diagnosis

The easiest way to diagnose nocturnal asthma is to check a bedtime peak flow and a peak flow on awakening.

If there is more than a 15 percent difference in your peak flow, you have significant variability that may be the cause of your symptoms. However, peak flow meters are not very sensitive to detect FEV1 changes. You and your health care provider may need to consider this and start a therapeutic trial.

Studies of asthma have revealed that as many as 74 percent of people with asthma have nighttime awakenings at least once per week, while as many as 64 percent may have asthma at night three or more times per week. Importantly, as many as 40 percent people with asthma experience symptoms nightly.

People with asthma may ignore nighttime symptoms as a sign of poor asthma control. In another study, 26 percent of patients who rated their asthma as "mild" reported experiencing asthma symptoms like chronic cough, wheezing, and a shortness of breath nightly. It is important to recognize these nighttime symptoms as poor control because a significant proportion of fatal asthma in adults and children from respiratory arrest and sudden death occurs between midnight and 8 a.m.

Physiology Behind Nocturnal Asthma

While no one knows for sure, asthma at night has been associated with:

  • Decreased nitric oxide levels: Because nitric oxide is a potent bronchodilator, decreased levels could possibly explain the increased nighttime symptoms.
  • Decreased beta 2-receptors: Both the number and function of beta 2 receptors—the receptors that are responsible for the bronchodilation that opens up your airways—decrease between 4 p.m. and 4 a.m.
  • Decreased steroid receptors: Similar to beta 2 receptors, both the numbers and function of steroid receptors—responsible for decreasing inflammation—decline at night. This decline may be responsible for increased inflammation due to a lack of response to your bodies naturally produced steroids or steroids prescribed by your doctor.
  • Abnormal pituitary function: Production of cortisol, a hormone made by the pituitary gland, declines overnight. This reduction is associated with a decline in FEV1. Treating patients who have low cortisol levels with hydrocortisone (a therapeutic steroid), is associated with improvements in FEV1.
  • Melatonin: Patients with nocturnal asthma have been noted to have low melatonin levels compared to patients without nocturnal asthma.

Treatment

Most patients with asthma at night meet criteria as moderate or severe persistent asthma according to NHLBI guidelines. You should be being treated according to these guidelines, but you and your provider may want to consider some of the following points if you think you have nocturnal asthma:

  • Inhaled glucocorticoids: In a study comparing 800 micrograms (four puffs of an Azmacort inhaler) at 3 p.m. each day to the traditional dose of one puff four times per day, the 3 p.m. dosing worked as well as the four times per day. When the dosing was changed to either 8:30 a.m. or 5 p.m. for convenience, the once daily 5:30 p.m. dosing still did better than the four times per day dosing, but the early morning dosing did worse.
  • Inhaled β2 adrenergic agonists: Long-acting β2 agonists, similar to your rescue inhaler but lasts six or more hours like salmeterol, have been shown to improve lung function overnight, sleep quality, and overall quality of life in nocturnal asthma.
  • Oral β2 adrenergic agonists: Oral forms of albuterol given as a slow release pill increase morning peak expiratory flow rates and decrease wheezing and shortness of breath.
  • Theophylline: Different types of theophylline have different properties. One that may particularly help nocturnal asthma is a preparation designed to have higher levels at night—like Uniphyl—when you are experiencing more symptoms. With this regimen, the theophylline levels decrease during the day and patients experience fewer side effects than with traditional dosing.
  • Treatment of other conditions that worsen asthma: A number of other medical conditions, like gastric reflux, sinus problems, and obesity, may worsen your asthma. If you are having nocturnal asthma symptoms, make sure that you are not at risk for these conditions.
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