Presence of asthma symptoms at night is very common. In one publication, nightime awakening of at least once a week happened in up to 74% of patients with asthma, approximately 40% experiencing nighttime symptoms on a nightly basis (Sutherland ER, JACI 2005, 116:1179). The presence of nocturnal symptoms in asthma impairs quality of life, increases asthma severity, and increases morbidity and mortality.

Many factors may contribute to this phenomenon. However, at the current moment, no definite mechanism has been found, however, asthma at night has been associated with :

• Airway inflammation
• Sleep state induced increased airway parasympathetic tone
• Decrease lung volume
• Airway smooth-muscle unloading
• Circadian modulation of respiratory function
  • Decrease expiratory flow rate
  • Reduced catecholaminergic activity
  • Reduced nonadrenergic; no cholinergic nervous system activity
  • Decreased cortisol
  • Increased inflammatory mediators
• Sleep-related environmental factors
  • Allergens
  • Cold air
• Comorbid disease
  • Obstructive sleep apnea
• Gastro esophageal reflux disease

Patients with nocturnal asthma fall into the criteria of uncontrolled asthma. Therefore, treatment of uncontrolled asthma is paramount in reducing nightime asthma. Many medications has been proven to be very useful in achieving good asthma control, such as inhaled corticosteroids, Inhaled ?2 adrenergic agonist, theophylline and leukotriene modifiers.

When patient presented with predominantly or solely nocturnal asthma symptoms, asthma medication given at specific timing can help to control nocturnal asthma (Chronotherapy).

• Inhaled glucocorticoids given at 3 – 5.30pm once daily.
• Long acting ?2-agonist at 8pm
• Theophylline sustained release given at 7pm once daily
• Oral corticosteroid 3pm once daily

A full investigation and treatment of other common conditions with worsening asthma at night for example, gastric reflux, OSA, heart failure, post-nasal drip should be done.

Although allergen exposure does not explain nocturnal asthma in general, dust mite, dog/cat, or other sensitivities must be considered in any given patient with nocturnal asthma, and interventions ranging from elimination to desensitization should be taken.

References:

• Greenberg H, Cohen RI. Nocturnal asthma: Curr Opinion of Pulmonol 2012; 18:57-62