Is a primarily nocturnal cough in a child indicative of postnasal drip?

Nocturnal Cough in Children is NOT Indicative of Postnasal Drip

A primarily nocturnal cough in a child should NOT be attributed to postnasal drip, as this concept lacks scientific validity in pediatric populations and nocturnal cough is more commonly associated with asthma, gastroesophageal reflux, or other airway pathologies. 1, 2

Why Postnasal Drip is Controversial in Children

The concept of postnasal drip (PND) causing cough in children is fundamentally flawed and should be abandoned:

• The definition of PND is inconsistent and it remains unclear whether it represents a symptom, a sign, or both, making it diagnostically unreliable 2
• PND was never a common etiology in prospective pediatric studies of chronic cough, appearing as a common cause in only two Turkish studies among multiple international cohorts 1
• The most plausible explanation for cough in children with increased postnatal secretions is that both reflect coexistent airway pathologies rather than a causal relationship 2
• The concept is inconsistent with the science of rheology and the actual meaning of "drip" 2

What Nocturnal Cough Actually Indicates

Primary Considerations:

Asthma or asthma-like conditions are the most important differential:

• Only one-third of children with isolated nocturnal cough (without wheezing, shortness of breath, or chest tightness) actually have an asthma-like illness 1
• Nocturnal cough is often used as a direct indicator of asthma, but this is an oversimplification 1
• Children hospitalized with asthma had objectively higher nocturnal cough counts than children with other illnesses 1

Gastroesophageal reflux disease (GERD) is another significant cause:

• Increased nocturnal cough has been reported with GER in children 1
• GERD can cause chronic cough without gastrointestinal symptoms in 50-75% of cases 3
• The European Respiratory Society notes that nocturnal cough is commonly associated with GERD 4

Snoring disorders and sleep-related breathing problems should be considered 1

Critical Diagnostic Pitfalls

The Unreliability of Nocturnal Cough Reporting:

• Parent-reported nocturnal cough correlates poorly with objective measurements (Cohen's kappa of only 0.3) 1
• Multiple studies have documented the unreliability of nocturnal cough reporting in children with asthma 1
• Healthy children attending school coughed 0 to 57 episodes per night (median of 0), while children with asthma reported to have troublesome cough had a median of only 6 episodes per night 1

Habit/Tic Cough Considerations:

Psychogenic or habit cough typically does NOT occur at night, which is the opposite pattern:

• Literature suggests that patients with psychogenic cough typically do not cough at night 1
• However, one objective study using a cough meter showed that cough during sleep can occur even in presumed psychogenic cough 1
• The presence or absence of nocturnal cough should NOT be used as sole criteria to diagnose or exclude psychogenic or tic cough 5

Diagnostic Approach

When evaluating a child with primarily nocturnal cough:

1. First, objectively assess for asthma:

   • Look for other asthma symptoms (wheezing, shortness of breath, chest tightness) 1
   • Consider spirometry with bronchodilator response if age-appropriate 1
   • Trial of asthma therapy may be diagnostic and therapeutic 1

2. Evaluate for GERD:

   • Ask about gastrointestinal symptoms, though their absence does not exclude GERD 3
   • Consider 24-hour pH monitoring if suspicion is high 3

3. Assess for sleep-disordered breathing:

   • Evaluate for snoring, witnessed apneas, restless sleep 1

4. Do NOT attribute the cough to postnasal drip based on:

   • Presence of nasal symptoms alone 2
   • Physical examination findings of posterior pharyngeal secretions 2
   • The timing of nocturnal cough 1, 2

Common Etiologies in Pediatric Chronic Cough

The most common causes identified in prospective studies are:

• Asthma or asthma-like conditions 1
• Protracted bacterial bronchitis (PBB) 1
• Natural resolution (resolved without specific diagnosis) 1

Notably absent from common pediatric etiologies are chronic bronchitis and idiopathic cough, which are common in adults 1