Correlation of peripheral blood BMAL1 level with non-motor symptoms in Parkinson’s disease patients

Objective This study aimed to quantify BMAL1 expression in the peripheral blood of patients with Parkinson’s disease (PD) and to evaluate its correlation with non-motor symptoms (NMS). We further assessed whether serum interleukin-6 and melatonin levels were associated with BMAL1 expression. Methods This study included 80 patients with PD and 80 age-and sex-matched healthy controls. General clinical information and scores on multiple NMS scales were collected. Peripheral blood BMAL1 expression was quantified using real-time quantitative polymerase chain reaction. Serum levels of melatonin and interleukin-6 were measured using enzyme-linked immunosorbent assay. Spearman’s correlation analysis was used to evaluate the associations between BMAL1 expression and the NMS scores. Results Compared to healthy controls, patients with PD exhibited significantly lower peripheral blood BMAL1 expression levels in the morning ( p = 0.005). BMAL1 levels were negatively correlated with the NMS Scale score ( r = −0.407, p < 0.001). Furthermore, higher BMAL1 levels were associated with better night-time sleep quality and cognitive function, whereas lower BMAL1 levels correlated with more severe anxiety and depression. A weak positive correlation was observed between BMAL1 expression and melatonin levels ( r = 0.267, p = 0.017). A significant negative correlation was found between BMAL1 expression and interleukin-6 level ( r = −0.603, p < 0.001). Conclusion In this cross-sectional study, peripheral blood BMAL1 expression at a single morning time point was lower in patients with PD and correlated with NMS severity, suggesting a potential pathway involving BMAL1 , melatonin, and inflammatory cytokines in NMS pathogenesis. Future studies with multiple time-point measurements are required to validate these findings.