268 - Environmental Stress and Salivary Cortisol Levels in Preterm Infants

Preterm infants are exposed to numerous environmental stressors as part of NICU care during the first week of life. Excessive stress or agitation can contribute to adverse outcomes such as intraventricular hemorrhage. The severity of NICU-induced stress can be quantified using the Neonatal Infant Stressor Scale (NISS), which is a validated composite score based on the number and intensity of hands-on events. The amount of stress over time can also be quantified by biomarkers of physiologic responses. In infants, serum and salivary cortisol levels rise after painful or noxious stimuli and decrease with soothing interventions. Validation of salivary cortisol as a non-invasive biomarker of stress could support efforts to identify and minimize harmful exposures for preterm infants.


Objective:

Our primary aim was to assess whether salivary cortisol levels are correlated with NISS scores in preterm infants during the first week of life. We also quantified the changes in both NISS scores and cortisol levels in the first week, and whether cortisol levels are associated with gestational age.


Design/Methods:

Preterm infants (n=27, birth weight < 1250 g and/or gestational age < 29 weeks) were included. Saliva samples were collected on day 0-3 (early) and day 4-7 (late) and cortisol concentrations measured by immunoassay. Modified NISS scores were assessed retrospectively for the 6 hours preceding each saliva collection.


Results:

NISS scores were not correlated with salivary cortisol levels at either time point. For individual infants, neither NISS scores nor cortisol levels differed between early and late measurements. Of note, there was a significant inverse relationship between NISS score and gestational age (p=0.037, Fig. 1). Additionally, infants born at < 28 weeks gestation tended to have higher early salivary cortisol levels than infants > 28 weeks (p=0.058, Fig. 2). 

Conclusion(s):

NISS scores are inversely related to gestational age, likely reflecting increased exposure to interventions and invasive procedures by the smallest infants. Although cortisol levels may also be elevated in infants < 28 weeks gestation, they do not correlate with NISS scores in this preliminary dataset. It is possible that cortisol is determined primarily by indices of medical instability rather than by environmental stressors in ELBW infants during the first week. Recruitment for this study is ongoing, and we plan to investigate these relationships further. Our interim findings suggest that direct observation-based scoring is essential for assessing and reducing noxious stimuli for ELBW infants in the first week.