Extremely preterm infants are most likely to have chronic respiratory sequelae following respiratory infections in early life, according to a report in the journal BMJ Open.

The findings come after researchers analyzed data from the national Swedish register to identify the vast majority of respiratory infections in the first year after birth that resulted in hospital admission between 1981 and 1995.

Children who developed early severe lung infections were individually matched for gestational age, region of birth, and the month and year of birth with children who did not develop such infections.

Subsequent development of asthma was identified from registers of inpatient and outpatient diagnoses, and a register of prescriptions was used to identify pharmaceutical treatments for asthma in children and young adults.

The team discovered that early respiratory infection was associated with asthma after age 5 across all gestational ages and that the highest magnitude association was among infants with a gestational age less than 28 weeks.