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 incidence occurring in infants less than 1 year old. 1

Definition and Epidemiology

• Bronchiolitis is a disorder commonly caused by viral lower respiratory tract infection in infants, characterized by acute inflammation, edema, and necrosis of epithelial cells lining small airways, and increased mucus production 1
• It is the most common lower respiratory infection in young children and the most common cause of hospitalization in those aged less than 1 year 1
• The American Academy of Pediatrics (AAP) clinical practice guidelines specifically define the target population for bronchiolitis management as children from 1 month through 23 months of age 1
• Approximately 90% of children are infected with Respiratory Syncytial Virus (RSV), the most common cause of bronchiolitis, within the first 2 years of life 2
• Up to 40% of children infected with RSV will experience lower respiratory tract infection during their initial infection 1

Age Distribution and Risk Factors

• The average age of children with bronchiolitis is around 10 months, with most cases occurring between 1-12 months of age 3
• The severity of bronchiolitis tends to be greater in younger infants (1-12 months) and decreases with age 3
• Infants younger than 12 weeks are at higher risk for severe disease 4
• Bronchiolitis leads to more than 90,000 hospitalizations annually in the United States, with most hospitalizations occurring in infants less than 1 year old 2
• A recent study found that younger age was significantly associated with ICU admission (69 days vs 110 days median age for non-ICU patients) 5

Clinical Presentation by Age

• In 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
  • More likely to have feeding difficulties due to respiratory distress 1

• In children 12-24 months:

  • Typically present with rhinitis and cough that may progress to wheezing and rales 1
  • Generally have less severe disease compared to younger infants 3
  • Better able to compensate for increased respiratory effort 1

High-Risk Groups

• Premature infants, especially those born before 32 weeks gestation 1, 5
• Children with hemodynamically significant congenital heart disease 1
• Children with chronic lung disease of prematurity 1
• Children with neuromuscular disease or immunodeficiency 1, 4
• Very low birth weight infants (under 1500 grams) have higher risk and severity of bronchiolitis 3

Clinical Course

• Bronchiolitis is typically self-limiting, with most children recovering within 2-3 weeks 1
• The mean time to cough resolution is 8-15 days 1
• 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
• Neonates (under 1 month) with bronchiolitis symptoms require special consideration due to their higher risk of severe disease and apnea 1, 3

Understanding the typical age range for bronchiolitis is crucial for appropriate diagnosis, risk assessment, and management decisions in pediatric patients presenting with respiratory symptoms.