Principal Investigator: Professor Jim Deuchars
Lead institution: University of Leeds
Award amount: £86,569
Stimulation of the vagus nerve through the skin of the ear, known as transcutaneous vagus nerve stimulation (tVNS), is a painless procedure.
Promoting healthy ageing by improving autonomic function through transcutaneous vagus nerve stimulation
The vagus nerve is a cranial nerve connecting the brain to other areas of body, such as the neck, heart, lungs and abdomen. It plays a key role in the autonomic nervous system, which regulates many important bodily processes and consists of a sympathetic and parasympathetic branch. Changes to autonomic function as people age — specifically decreases in parasympathetic nervous activity and increases in sympathetic nervous activity — are associated with a number of health problems including depression, cardiovascular disease and decreased gastrointestinal function.
Rebalancing autonomic activity through electrical stimulation of the vagus nerve, the main output of the parasympathetic nervous system, is an approved or proposed therapy for the treatment of multiple conditions including depression, epilepsy and heart failure. However, vagus nerve stimulation (VNS) is an invasive procedure associated with several technical and surgical difficulties, as well as potential side effects for patients.
One small branch of the vagus nerve comprises a small sensory distribution at the cutaneous ear. Stimulation of the vagus nerve through the skin at this site, known as transcutaneous VNS (tVNS), is currently being investigated as a non-invasive alternative to VNS. An interesting outcome of this early work is the suggestion that tVNS may be most effective in older patients, who demonstrate greater sympathetic activity and for whom a greater shift in autonomic activity is possible.
This project aimed to investigate the effectiveness of autonomic rebalancing through tVNS in improving cardiovascular function, gastrointestinal function, mood and quality of life scores in an older population. To achieve this, volunteers aged 55 and over were recruited and the procedure was tested through two treatment regimes: a) a single acute 15-minute session of tVNS, compared to a sham treatment, and b) chronic tVNS treatment, consisting of a daily 15-minute session for two weeks. The researchers were interested in what effect these two regimes had on autonomic activity, as well as whether chronic treatment led to more persistent effects and improved mood and quality of life.
Compared to volunteers subjected to a sham treatment, those given an acute session of tVNS exhibited increased vagus nerve activity and baroreflex sensitivity (BRS), an indicator of improved neurological and cardiovascular function.
Volunteers who undertook daily sessions of tVNS for two weeks also demonstrated increases in vagal activity. In addition, daily tVNS led to enhancements in aspects of health-related quality of life and mood. For example, volunteers reported improved tension, depression, vigour and mood disturbance scores after the two weeks.
Importantly, several factors were found to predict volunteers’ response to treatment:
- Post-treatment measures of autonomic balance were more pronounced in volunteers who demonstrated greater baseline indicators of sympathetic nervous activity
- Participants with high tension, depression, anger and confusion scores at the start of the study demonstrated greater improvements in mood following two weeks of tVNS than participants with low scores
Overall, these results provide the first evidence that daily tVNS may be used to improve age-related autonomic changes, quality of life and mood in older people. They also suggest that, with further work, it may be possible to identify those individuals who will most benefit from treatment, so increasing the potential impact of the procedure.
The full findings of the project were recently published in the journal ‘Aging’ and can be read here. This publication has since received considerable media attention and has been covered in the press, on radio and through social media outlets. For an example of just one of these, take a read of the recent BBC News article.