Ross Hauser, MD.
Heart rate variability (HRV) is an important measure of autonomic nervous system health. HRV measures the variation in time between heartbeats rather than measuring how fast the heart beats. A higher HRV generally reflects a healthy, resilient nervous system that can adapt to physical and emotional stress and quickly return to a calm state. In contrast, a low HRV indicates reduced adaptability and has been linked to chronic stress, anxiety, depression, cardiovascular disease, diabetes, chronic pain, and an increased risk of illness and premature death.
The vagus nerve help regulates HRV. The vagus nerve provides the majority of the parasympathetic (“rest-and-digest”) control of the heart. When vagal activity is strong, heart rate variability increases. When vagal function is impaired by physical, emotional, or structural stress, HRV declines. Because of this close relationship, HRV has become a widely accepted, noninvasive measure of autonomic nervous system function.
HRV testing can objectively measure how different stressors affect the nervous system. Emotional stress, cognitive challenges, loud noises, and even specific neck movements can produce measurable changes in autonomic function. In some individuals with cervical instability, certain neck positions trigger marked increases in sympathetic activity and reductions in vagal tone, suggesting that structural problems in the cervical spine may contribute to autonomic dysfunction.
Because HRV can be measured repeatedly over time, it also provides an objective way to monitor treatment response. Improvements in cervical alignment and stability have been associated with improved HRV, suggesting enhanced autonomic regulation and a greater ability to tolerate both physical and emotional stress. As a result, functional HRV testing may be a valuable tool for evaluating autonomic dysfunction and tracking recovery in patients with chronic neck pain and cervical instability.
HRV Research
An October 2023 study published in the International Journal of Environmental Research and Public Health (1) involving 54 participants found that people with a more positive outlook (high trait positive affect) had significantly higher heart rate variability (HRV), reflecting stronger parasympathetic (vagal) activity and better autonomic nervous system regulation. During prolonged mental stress, including demanding cognitive and social stress tasks, these individuals also had lower heart rates and recovered more effectively from stress. The findings suggest that a positive emotional outlook is associated with greater autonomic resilience, improved emotional regulation, and an enhanced ability to cope with physical and psychological stress.
Research suggests that disorders of the cervical spine can also affect HRV. In a recent case-control study published in the Public Library of Science (2), one of 80 patients with chronic nonspecific neck pain and 80 healthy controls, patients with neck pain had significantly lower HRV than healthy individuals.
Greater pain severity, anxiety, and cervical disc herniation were all associated with further reductions in HRV, and more severe upper cervical instability was also significantly associated with lower HRV. This suggests that structural cervical instability may contribute to autonomic nervous system dysfunction. The researchers concluded that HRV may serve as an objective biomarker for evaluating chronic neck pain and its effects on the autonomic nervous system.
Reduce vagal activity, HRV, and sleep disruptions
A June 2026 study (3) of 5,225 adults found that people with both insomnia and obstructive sleep apnea had greater autonomic nervous system dysfunction than those with either condition alone. They showed lower heart rate variability (HRV), indicating reduced parasympathetic (vagus nerve) activity. During follow-up, nearly one-third of people with both insomnia and obstructive sleep apnea died. Higher HRV, particularly a measure called heart rate deceleration capacity, was associated with a lower risk of death. The researchers concluded that reduced vagus nerve function may contribute to the increased health risks seen in people with both insomnia and sleep apnea, and that HRV may help identify those at greatest risk.
Because HRV can be measured repeatedly over time, it also provides an objective way to monitor treatment response. Improvements in cervical alignment and stability have been associated with improved HRV, suggesting enhanced autonomic regulation and a greater ability to tolerate both physical and emotional stress. As a result, functional HRV testing may be a valuable tool for evaluating autonomic dysfunction and tracking recovery in patients with chronic neck pain and cervical instability.
Research has shown that positive emotional states and slow diaphragmatic (“resonance”) breathing, typically around six breaths per minute, significantly increase HRV by enhancing vagal activity. Conversely, emotional stress, chronic pain, and cervical spine disorders that affect the upper neck may reduce HRV, reflecting impaired autonomic regulation.
Electrical stimulation to improve automatic function
A July 2026 study (4) of 20 healthy adults found that noninvasive electrical stimulation of the neck (TCES) can increase vagus nerve activity and improve autonomic nervous system function, as measured by heart rate variability (HRV). The best stimulation settings were different for each person, and stronger stimulation generally worked better than weaker stimulation. Right-sided and bilateral stimulation produced better results than left-sided stimulation. The greatest increase in HRV occurred after about 4 minutes of treatment, with little added benefit from longer sessions. The researchers concluded that TCES may help improve autonomic function, but treatment should be personalized for each individual.
A January 2026 study (5) of 60 healthy young women found that noninvasive vagus nerve stimulation using a manual neck technique improved attention and cognitive performance. Left-sided stimulation also increased cardiac coherence and participants’ sense of emotional control. The researchers cautioned that the treatment did not significantly change heart rate variability (HRV), but that noninvasive vagus nerve stimulation may enhance cognitive and emotional function.
Further reading
Ross Hauser, MD Reviews Cervical Spine Instability and Potential Effects on Brain Physiology
References
1 Sveinsdóttir SÞ, Jóhannsdóttir KR. Is Positive Affect as a Trait Related to Higher Heart Rate Variability in a Stressful Situation?. International Journal of Environmental Research and Public Health. 2023 Oct 13;20(20):6919. [Google Scholar]
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