Effects of cold stimulation on cardiac-vagal activation: Randomized controlled trial with healthy participants (Preprint)

Abstract

Background:The global stress epidemic has not yet been adequately tackled with digital technology by catering to healthy individuals who desire to reduce their acute stress levels. There is a need to investigate physiological mechanisms in the body that can be addressed to induce relaxation through technology. Research has shown that physiological mechanisms embodied in the facial and neck regions are effective for diminishing stress related symptoms. The study described in this paper expands on these areas with the design for a wearable in mind. As this study charts new territory in research, it also represents a first evaluation of the viability for a wearables concept to reduce stress. We inquire into the effects of cold stimulation on heart rate (HR) and heart rate variability (HRV) in the neck region using a Thermode device. Objective:The objectives of this study were to assess whether (a) HRV is increased and (b) HR is decreased during a cold stimulation compared to a (non-stimulated) control condition. Effects were in particular expected in the neck and cheek regions and less in the forearm area (c). Methods:Participants were seated in a lab chair and tested with cold stimulation on the right side of the body. The Thermode was placed on the neck, cheek and forearm. Participants' electrocardiogram was recorded and subsequently analyzed. The study was a fully randomized, within subject design. The cold stimulation was applied in 16 s intervals over 4 trials per body location. The control condition proceeded exactly like the cold condition, except the thermal variable was manipulated to remain on the baseline temperature. HR was expressed in terms of IBIs per msec, and rMSSD was used to index HRV. Data were analyzed using a repeated measurements analysis of variance approach with two repeated measurements factors, i.e. Body Location (neck, cheek, forearm) and Condition (cold, control) Results:The analyses of data of 61 participants (on exclusion of outliers) showed a main effect for body location for HR and HRV, a main effect for condition for HR and HRV and an interaction effect for condition and body location for HR and HRV. The results obtained demonstrate a pattern of cardiovascular reactivity to cold stimulation, suggesting an increase in cardiac-vagal activation. The effect was found to be significant for cold stimulation in the lateral neck area. Conclusion:The results confirmed our main hypothesis, which completes only the first step in the evaluation procedure of the wearables concept for stress reduction. Future studies should focus on a stress condition and collect self-report data on perceived stress levels.