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Heart rate variability and salivary cortisol in very preterm children during school age
Natalie Urfer-Maurer1, Sebastian Ludyga2, Tobias Stalder3
1University of Basel, Department of Psychology, Basel, Switzerland.
Insights
Children born very preterm show altered autonomic nervous system (ANS) function, impacting stress response. Findings suggest a connection between the ANS and the hypothalamic-pituitary-adrenal (HPA) axis in these children.
Area of Science:
- Neuroscience
- Developmental Pediatrics
- Psychoneuroendocrinology
Background:
- The autonomic nervous system (ANS) regulates stress response and adaptability.
- Early life stress can alter ANS function long-term.
- Preterm birth is a significant early life stressor with potential long-term physiological consequences.
Purpose of the Study:
- To investigate differences in autonomic nervous system (ANS) function between children born very preterm and full-term.
- To examine the association between ANS function and the hypothalamic-pituitary-adrenal (HPA) axis in these children.
- To explore the interplay between the two main human stress systems in very preterm infants.
Main Methods:
- Polysomnography (PSG) to assess autonomic function via heart rate variability (HRV) parameters (LF, HF, Tot Pow, LF/HF ratio) during wake and sleep stages.
- Salivary cortisol measurements to evaluate hypothalamic-pituitary-adrenal (HPA) axis activity post-awakening.
- Comparison of HRV and cortisol levels between 54 very preterm (<32 weeks) and 67 full-term children (7-12 years old).
Main Results:
- Children born very preterm exhibited a lower LF/HF ratio during wake and stage 2 sleep compared to full-term controls.
- Higher LF, Total Power, and LF/HF ratio during wake, stage 2, and REM sleep were associated with increased post-awakening cortisol secretion.
- These findings indicate long-term ANS alterations persisting after very preterm birth.
Conclusions:
- Very preterm birth is associated with long-term alterations in autonomic nervous system (ANS) function.
- A significant relationship exists between ANS activity and HPA axis function in children.
- The study supports the concept of mutual feedback between the ANS and HPA axis in the human stress system.
Abstract:
The autonomic nervous system (ANS) plays a major role in the human stress response and reflects physical and psychological adaptability to a changing environment. Long-term exposure to early life stressors may alter the function of the ANS. The present study examines differences in the ANS between children born very preterm and full-term as well as the association between the ANS and the hypothalamic-pituitary-adrenal (HPA) axis, the other main branch of the human stress system. Fifty-four healthy children born very preterm (<32nd gestational week) and 67 full-term children aged 7-12 years provided data for the present study. Polysomnography (PSG) assessments were obtained during a night at the children's home in lying position at rest (wake) and during different sleep stages (stage 2 sleep, slow wave sleep, rapid-eye-movement sleep). Autonomic function was assessed by use of heart rate variability, specifically low frequency power (LF), high frequency power (HF), total spectral power (Tot Pow), and the LF/HF ratio. HPA axis activity was measured using salivary cortisol the next morning at awakening, 10, 20, and 30min later. Children born very preterm had lower LF/HF ratio during wake and stage 2 sleep compared to full-term children. Moreover, higher LF, Tot Pow, and LF/HF ratio during wake, stage 2 sleep, and REM sleep were related to more post-awakening cortisol secretion. The present study provides evidence on long-term ANS alterations after very preterm birth. Moreover, findings suggest a relation between the ANS and the HPA axis and therefore support the notion of mutual feedback between the two human stress systems.