What is the typical age range for bronchiolitis (inflammation of the bronchioles)?

Bronchiolitis Age Range

Bronchiolitis primarily affects children from 1 month through 23 months of age, with the highest risk of severe disease and hospitalization occurring in infants less than 1 year old. 1

Definition and Epidemiology

• Bronchiolitis is a viral lower respiratory tract infection characterized by inflammation, edema, and necrosis of epithelial cells lining small airways, along with increased mucus production 1
• It is the most common lower respiratory infection in young children and the leading cause of hospitalization in those under 1 year of age 1
• Approximately 90% of children are infected with Respiratory Syncytial Virus (RSV), the primary cause of bronchiolitis, within the first 2 years of life 1, 2

Age Distribution

• The American Academy of Pediatrics (AAP) specifically defines the target population for bronchiolitis management as children from 1 month through 23 months of age 1
• Most hospitalizations occur in infants less than 1 year old 1
• Infants younger than 12 weeks are at higher risk for severe disease 1
• Neonates (under 1 month) with bronchiolitis symptoms require special consideration due to their higher risk of severe disease and apnea 1

Clinical Presentation by Age

• Infants 1-12 months:
  • More likely to present with increased work of breathing, including tachypnea, nasal flaring, and intercostal retractions 1
  • Higher risk of apnea, particularly in those younger than 1 month and in premature infants 1
  • Severity of bronchiolitis is greater in this younger age group 3
• Children 12-24 months:
  • Typically present with rhinitis and cough that may progress to wheezing and rales 1
  • Generally able to compensate for increased respiratory effort better than younger infants 1
  • Severity tends to decrease with age 3

High-Risk Groups

• Premature infants, especially those born before 32 weeks gestation 1
• Children with hemodynamically significant congenital heart disease 1, 2
• Children with chronic lung disease of prematurity 1, 2
• Children with neuromuscular disease or immunodeficiency 1
• Infants with birth weight under 1500 grams 3

Clinical Course

• Bronchiolitis is typically self-limiting, with most children recovering within 2-3 weeks 1, 4
• The mean time to cough resolution is 8-15 days 1, 4
• 90% of children are cough-free by day 21 1
• Children with persistent symptoms beyond 4 weeks may represent a different clinical problem, sometimes termed "post-bronchiolitis syndrome" 1

Important Considerations

• The AAP guidelines specifically exclude children with immunodeficiencies, underlying respiratory illnesses, neuromuscular disease, or hemodynamically significant congenital heart disease from general management recommendations 1
• Children outside the 1-24 month age range may develop bronchiolitis-like illnesses but may have different clinical presentations, management needs, and outcomes 1
• Bronchiolitis is the most frequent cause of hospital admission in children less than 1 year of age, with an estimated 150 million cases worldwide annually 5
• Younger age is significantly associated with ICU admission (median age 69 days for ICU vs. 110 days for non-ICU admissions) 6

Pitfalls to Avoid

• Failing to recognize that neonates (under 1 month) with bronchiolitis require special consideration due to higher risk of severe disease 1
• Not identifying high-risk infants who may need more aggressive management or prophylaxis 1, 2
• Overlooking that bronchiolitis in children outside the typical age range may represent a different clinical entity 1
• Underestimating the severity in younger infants (1-12 months) who are at higher risk for complications 1, 3, 6