Presence and progression of non-motor symptoms in relation to uric acid in de novo Parkinson's disease

Background and purpose: Uric acid (UA) has been studied extensively as a valuable biomarker of Parkinson's disease (PD), but its relationship with non-motor symptoms (NMS) in de novo PD has been poorly investigated. Our aim was to evaluate the usefulness of baseline serum UA as a marker of NMS progression in newly diagnosed PD. Methods: Sixty-nine newly diagnosed PD patients were enrolled. At baseline, all patients completed the NMS questionnaire (NMSQuest), and serum UA levels were measured. After 2 years, the NMSQuest was completed again and patients were categorized into four groups: NMS improvement (domain involvement at baseline but not at 2-year follow-up visit), NMS absence (domain not involved at baseline or 2-year follow-up visits), NMS presence (domain involvement both at baseline and 2-year follow-up visits) and NMS worsening (domain not involved at baseline but involved at 2-year follow-up). Results: anova with post hoc Bonferroni correction showed that patients with NMS absence presented significantly higher UA values than patients with NMS presence with regard to the attention/memory (P = 0.023), depression/anxiety (P = 0.028) and cardiovascular domains (P = 0.002), whilst no differences were found with regard to both the NMS improvement and worsening groups. In addition, multinomial regression analysis showed that the lowest tertile of NMS progression presented higher UA levels (P = 0.023; odds ratio 0.488) compared with patients with greater NMS progression. Conclusions: This is the first report of a relationship between serum UA and presence/progression of multiple NMS in de novo PD, providing additional evidence of the reliability of UA as a biomarker of PD and opening new insights on PD neuroprotection.