Objective: Little is known about the developmental trajectory of cortisol levels in preterm infants after hospital discharge.
Study design: In a cohort of 225 infants (gestational age at birth <33 weeks) basal salivary cortisol levels were compared in infants born at extremely low gestational age (ELGA, 23-28 weeks), very low gestational age (29-32 weeks), and term (37-42 weeks) at 3, 6, 8, and 18 months corrected age (CA). Infants with major neurosensory or motor impairment were excluded.
Results: At 3 months CA, salivary cortisol levels were lower in both preterm groups compared with the term infants (P = .003). Conversely, at 8 and 18 months CA, the ELGA infants had significantly higher basal cortisol levels than the very low gestational age and term infants (P = .016 and P = .006, respectively).
Conclusions: In ELGA infants, the shift from low basal cortisol levels at 3 months to significantly high levels at 8 and 18 months CA suggests long-term "resetting" of endocrine stress systems. Multiple factors may contribute to these higher cortisol levels in the ELGA infants, including physiological immaturity at birth, cumulative stress related to multiple procedures, and mechanical ventilation during lengthy hospitalization. Prolonged elevation of the cortisol "set-point" may have negative implications for neurodevelopment and later health.