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

Background:
The experience of psychological stress has not yet been adequately tackled with digital
technology by catering to healthy individuals who wish to reduce their acute stress levels.
For the design of digitally mediated solutions, physiological mechanisms need to be
investigated that have the potential to induce relaxation with the help of technology.
Research has shown that physiological mechanisms embodied in the face 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. A 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 testing location. The control condition proceeded exactly like the cold
condition, except the thermal variable was manipulated to remain on the baseline
temperature.
HR was measured in msec IBI. rMSSD analyses were 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 data analysis 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. This sets the stage for further investigations
of the stress reduction potential in the neck region by developing a wearable prototype
that can be used for cold application. Future studies should include a stress condition, test
for a range of temperatures and durations, and collect self-report data on perceived stress
levels to advance current findings.