Autonomic and adrenocortical reactivity and buccal cell telomere length in kindergarten children

Abstract

Objective: To examine associations between autonomic nervous system and adrenocortical reactivity to laboratory stressors and buccal cell telomere length (BTL) in children.

Methods: The study sample comprised 78 children, aged 5 to 6 years, from a longitudinal cohort study of kindergarten social hierarchies, biologic responses to adversity, and child health. Buccal cell samples and reactivity measures were collected in the spring of the kindergarten year. BTL was measured by real-time polymerase chain reaction, as the telomere-to-single-copy gene ratio. Parents provided demographic information; parents and teachers reported children's internalizing and externalizing behavior problems. Components of children's autonomic (heart rate, respiratory sinus arrhythmia [RSA], and preejection period [PEP]) and adrenocortical (salivary cortisol) responses were monitored during standardized laboratory challenges. We examined relationships between reactivity, internalizing and externalizing behaviors, and BTL, adjusted for age, race, and sex.

Results: Heart rate and cortisol reactivity were inversely related to BTL, PEP was positively related to BTL, and RSA was unrelated to BTL. Internalizing behaviors were also inversely related to BTL (standardized β = -0.33, p = .004). Split at the median of reactivity parameters, children with high sympathetic activation (decreasing PEP), and parasympathetic withdrawal (decreasing RSA) did not differ with regard to BTL. However, children with both this profile and high cortisol reactivity (n = 12) had significantly shorter BTL (0.80 versus 1.00; χ² = 7.6, p = .006), compared with other children.

Conclusions: The combination of autonomic and adrenocortical reactivity was associated with shorter BTL in children. These data suggest that psychophysiological processes may influence, and that BTL may be a useful marker of, early biologic aging.

Figure 1

Cross-classification of autonomic nervous system (ANS) reactivity and adrenocortical reactivity in the Peers and Wellness Study, n = 78. PEP = preejection period; RSA = respiratory sinus arrhythmia; HPA = hypothalamic-pituitary-adrenal.

Figure 2

Standardized reactivity difference scores* and buccal cell telomere length (BTL) in the Peers and Wellness Study, n = 78. * Heart rate reactivity was inversely related to BTL. Externalizing symptoms were not related to BTL. PEP = preejection period; T/S = telomere repeat copy number to single-copy gene copy number; ANS = autonomic nervous system; RSA = respiratory sinus arrhythmia.

Figure 3

Reactivity profiles and buccal cell telomere length. * Children with reciprocal sympathetic activation and high cortisol response differed from other reactivity profiles (T/S ratio, 0.80 versus 1.00; χ² = 7.5, p = .0006). T/S = telomere repeat copy number to single-copy gene copy number; ANS = autonomic nervous system; HPA = hypothalamic-pituitary-adrenal.