Correlation of Preterm Infant Salivary Cortisol Levels with Scores on the Neonatal Infant Stressor Scale

Repeated stress during the early period of infant development is hypothesized to produce long-lasting effects on
cognitive, behavioral, and somatic development. Despite efforts to nurture preterm infant development during the
life-saving birth hospitalization, the neonatal intensive care unit (NICU) is a stressful environment. Variation in cortisol
levels reflects multiple stressors during the neonatal period, potentially impacting development of immature hypothalamic, pituitary and adrenal axes. Assessing the stress response of neonates to noxious stimuli can be challenging. The
Neonatal Infant Stressor Scale (NISS) is one tool used to quantify neonatal stress for clinical and research purposes. The
scale consists of 35 acute items and 19 chronic items that are thought to capture stressful events that were chosen by
NICU caregiver estimation of stressful events during the NICU hospitalization and. To our knowledge, scores on the
NISS have not previously been compared to physiologic biomarkers of infant stress.
In this study, we compared acute and chronic NISS scores to an accepted biomarker of infant stress response, salivary cortisol, in a cohort premature infants born 28-0/7–32-6/7 weeks gestation through the course of the NICU
hospitalization.
In preliminary analysis, we examined 143 salivary specimens from 68 patients. Using a Pearson correlation analysis and
mixed-effects model we concluded that both acute and chronic NISS scores were significantly correlated with salivary
cortisol (P-values < 0.001). The mixed-effects model with random coefficients for infant and family revealed significant