The impact of exercise and/or photobiomodulation relative to usual care on metabolic syndrome severity in people with Parkinsons disease: a randomised crossover study

Background: Parkinson’s disease (PD) is a progressive neurodegenerative disorder affecting about 150,000 people in Australia. Metabolic syndrome (MetS) has been postulated to play a role in the progression of Parkinson’s disease (PD). Aerobic exercise (AE) is also known to be a potent therapy to ameliorate MetS severity, as well as motor and non-motor symptoms of PD. However, long-term exercise adherence in this population is poor. Photobiomodulation (PBM) may also be considered as an exercise mimetic, but more work is required to confirm this hypothesis. Study Objective: We aimed to evaluate the impact of AE and/or PBM relative to usual care on MetS severity in individuals with PD. Hypothesis: We hypothesised that the combined use of these treatment paradigms could induce more MetS severity amelioration in PD. METHODOLOGY: This study included 20 participants (40-80 years) with idiopathic PD. Participants were randomised into four groups: i) Group-A-B-C-D (n=5); ii) Group-B-D-A-C(n=5); iii) Group-C-A-D-B (n=5); iv) Group-D-C-B-A (n=5), where A,B,C, and D represents 8-week PBM, AE, PBM+AE, and SHAM, each separated by a 4-week wash-out. The PBM+AE group was only prescribed ≤50% of the exercise sessions/week relative to the AE group. Z-scores were derived from levels of MetS risk factors at pre- and post-intervention. Responders to a clinically significant change in MetS z-score were classified as those reflecting a change of at least 0.48 following the intervention. Data and summary of results: Our analysis included 14 participants who have completed at least one treatment period (PBM, n=14; AE, n=12; PBM+AE, n=13; SHAM, n=13). There was no statistically significant difference between groups in MetS z-score change from pre- to post-intervention (p=0.34). However, The AE group showed the greatest proportion of responders to a clinically significant change in MetS z-score (67%, 8/12) compared to PBM+AE (46%, 6/13), PBM (43%, 6/14), and SHAM (31%, 4/13). Conclusion: Our study suggests that AE may be more efficacious in improving MetS severity relative to the combined treatment, PBM alone, or usual care in people with PD. However, our study also indicates that PBM may be a suitable adjunct/alternative non-pharmacological therapy to improve MetS severity, particularly in those contraindicated to exercise. These findings are clinically significant as ameliorating MetS severity may potentially impede PD progression. This study was funded by The Hospital Research Foundation (THRF) Parkinsons This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.