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Why is asthma worse at night?

Medically reviewed by Sally Chao, MD. Last updated on Jan 23, 2024.

Official answer


Exactly why asthma tends to get worse at night is not fully understood, but several theories exist. “Nocturnal asthma” may be due to one or more factors that interact:

  • The tubes that carry air into your lungs and back out again (airways) grow more resistant to air flow during the night due to normal hormonal fluctuations. Airway function tends to decrease during sleep (and daytime) in people with nocturnal asthma. This is known as reduced forced expiratory volume (FEV) rate.
  • Higher levels of blood cells known to promote inflammation, including eosinophils and neutrophils, are present in the blood of individuals with nighttime asthma symptoms.
  • Exposure to triggers at night such as dust mites in the bedding or mattress, or animal dander if pets sleep in the bed, may trigger nighttime symptoms. Some people may also be triggered by mold, pollen or cold air.
  • Sleep position may also play a role. Back sleeping puts extra pressure on the chest and lungs.
  • Nighttime flares may also be due to poorly controlled asthma by day.

Alone or together, all of these factors can set the stage for nighttime asthma symptoms, including coughing, wheezing and chest tightness that can disrupt sleep.

More than 75 percent of individuals with asthma report nighttime symptoms.

Nocturnal asthma tends to be associated with more severe disease. Researchers continue to explore other risk factors that may give rise to nocturnal asthma symptoms.

Keeping a rescue medication in easy reach at night, taking steps to control bedroom asthma triggers and discussing nighttime symptoms with a doctor can help improve sleep and stave off nighttime asthma flare-ups. Asthma treatment, which typically involves a long-term daily controller/s plus another rescue inhaler for asthma attacks, may need to be adjusted to control nighttime asthma symptoms.

  1. National Sleep Foundation. Asthma and Sleep. Available at: [Accessed November 13, 2020].
  2. Levin AM, Wang Y, Wells K, et al. Nocturnal Asthma and the Importance of Race/Ethnicity and Genetic Ancestry. American Journal of Respiratory and Critical Care Medicine. 2014;190(3): 266-273.
  3. The Asthma UK and British Lung Foundation Partnership. Nocturnal asthma. September 2019. Available at: [Accessed November 13, 2020].

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