Research Article Vagal Nerve Stimulation-Modulation of the Anti-Inflammatory Response and Clinical Outcome in Psoriatic Arthritis or Ankylosing Spondylitis C. Brock , 1 S. E. Rasmussen , 2 A. M. Drewes , 2 H. J. Møller , 3 B. Brock , 4 B. Deleuran , 2 A. D. Farmer , 5,6 and M. Pfeiffer-Jensen 2,7 1 Mech-Sense, Department of Gastroenterology and Hepatology, Clinical Institute, Aalborg University Hospital, Aalborg, Denmark 2 Department of Rheumatology, Aarhus University Hospital, Aarhus, Denmark 3 Department of Clinical Biochemistry, Aarhus University Hospital, Denmark 4 Steno Diabetes Center Copenhagen, Region Hovedstaden, Gentofte, Denmark 5 Centre for Trauma and Neuroscience, Blizard Institute, Wingate Institute of Neurogastroenterology, Barts and the London School of Medicine & Dentistry, Queen Mary University of London, London, UK 6 Institute of Applied Clinical Sciences, University of Keele, Stoke on Trent, UK 7 Copenhagen Center for Arthritis Research (COPECARE), Center for Rheumatology and Spine Diseases, Rigshospitalet, Glostrup, Copenhagen, and Department of Clinical Medicine, University of Copenhagen, Denmark Correspondence should be addressed to C. Brock; christina.brock@rn.dk Received 22 March 2021; Accepted 3 May 2021; Published 27 May 2021 Academic Editor: Rômulo Dias Novaes Copyright © 2021 C. Brock et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives. The vagal nerve exerts an essential pathway in controlling the cholinergic anti-inflammatory reflex. Thus, the study is aimed at investigating the acute effect of a noninvasive transcutaneous vagus nerve stimulation on clinical disease activity and systemic levels of inflammation in patients with psoriatic arthritis or ankylosing spondylitis. Methods. Twenty patients with psoriatic arthritis (PsA) and 20 patients with ankylosing spondylitis (AS) were included and stimulated bilaterally with a handheld vagal nerve stimulator for 120 seconds 3 times a day for 5 consecutive days. All patients were in remission. Cardiac vagal tone, clinical scores, CRP, and cytokine levels were assessed. Results. In PsA and AS, decreased heart rate was observed, confirming compliance. Furthermore, in PsA, a clear reduction of clinical disease activity associated with a 20% reduction in CRP was shown. In AS, a reduction in interferon-γ, interleukin- (IL-) 8, and 10 was shown. No side effects were described. Conclusion. This open-label study provides support for an anti-inflammatory effect of transcutaneous vagus nerve stimulation in patients with psoriatic arthritis and ankylosing spondylitis. The modulated immune response and reduced disease activity and CRP-levels raise the fascinating possibility of using neuromodulation as an add-on to existing pharmacological treatments. 1. Introduction Psoriatic arthritis (PsA) and ankylosing spondylitis (AS) are chronic autoimmune diseases characterized by peripheral and spinal joint inflammation. The global prevalence of PsA and AS is approximately 0.5% [1–3], and the chronic inflammation of peripheral and spinal joints in PsA and AS leads to various degrees of impaired functionality associ- ated with increased risks of cardiovascular comorbidities and mortality [4–6] and substantial socioeconomic expenses [7]. Currently, PsA and AS are typically treated with nonste- roidal anti-inflammatory drugs (NSAIDs) and/or disease- modifying antirheumatic drugs (DMARDs) such as metho- trexate (MTX) [8] and targeted biological therapies, i.e., tumour necrosis factor-alpha (TNF-α) inhibitors, interleu- kin- (IL-) 17, and IL-12/23 inhibitors [9–12]. Frequent blood monitoring of the disease activity and presence of opportu- nistic infections is needed, and whilst most patients respond to these expensive treatments, a proportion of patients do not [13–15]. Hindawi Mediators of Inflammation Volume 2021, Article ID 9933532, 9 pages https://doi.org/10.1155/2021/9933532