Visually detected NREM Stage 2 sleep spindles in kindergarten children are associated with stress challenge and coping strategies

Abstract

Objectives. Sleep EEG spindles are linked to efficient cortical-subcortical connectivity and intellectual abilities. The aim of the present study was to investigate the relationship of spindle activity to psychosocial stress response and coping strategies in healthy kindergarten children. Methods. In a cross-sectional study of 41 5-year old kindergarten children we examined stress-induced hypothalamic-pituitary-adrenocortical (HPA) system activity by saliva cortisol measurements and sleep regulation by sleep EEG-monitoring. Stress response was measured during the application of a standardized psychological challenge appropriate at this age. NREM S2 sleep EEG spindles were visually scored and put into relation to coping and HPA activity parameters. Results. An increased total number of NREM S2 sleep spindles correlated positively with increased high ego-involvement strategies such as “positive emotions”. By contrast, total number of NREM S2 sleep spindles correlated negatively with low ego-involvement strategies such as “denial” and “avoidance”. Stress induced HPA-activity correlated positively with coping strategies with high ego-involvement; while there was no correlation with low ego-involvement strategies. Conclusions. Total number of visually detected NREM S2 sleep spindles is elevated in children with coping involving positive, high ego-involvement; in contrast, low ego-involvement during stress is associated with reduced total number of NREM S2 sleep spindles.

Key words::

• Sleep spindles
• polysomnography
• kindergarten children
• stress challenge
• free saliva cortisol

Acknowledgments

We thank R. Hartmann, C. Keppler, L. Kohler, B. Krebs, and P. Walter for their support in data collection. We are deeply grateful to Vladimir Djurdjevic and Marielle Köenig for technical support and data elaboration. We also thank the CortLab of the University of Trier (Germany) for analyzing the cortisol samples. Finally, we thank all participating children, parents, and kindergarten teachers for their support of the study.

Statement of Interest

The work was supported by the Swiss National Science Foundation SNF No. 32-68193.02 (MH) as well as SNF No. 32-66778.01 (KvK). The SNF had no further role in the analysis and interpretation of the data, the writing of the report, or the decision to submit the paper for publication. All authors declare no conflict of interest.

Notes

¹To further test, if and to which extent avoidance, denial, positive emotion (MSSB) and prosocial behavior and impulsivity (BPI) did correlate with the mere length of NREM S2 sleep and NREM S2 sleep spindle density respectively, correlations were performed. Except for impulsivity (r = −0.40, P < 0.05), all other correlation coefficients were <0.30 and did not reach statistical significance.