Clinical Characteristics, Iron Metabolism and Neuroinflammation: New Insight into Excessive Daytime Sleepiness in Parkinson's Disease.

BACKGROUND

To investigate the clinical characteristics, iron metabolism and neuroinflammation in Parkinson's disease (PD) patients with excessive daytime sleepiness (EDS).

METHODS

We studied 379 patients with PD and 30 age-matched controls. All subjects were evaluated by Epworth sleepiness scale (ESS) and a series of rating scales and were divided into PD-EDS and PD-NEDS groups according to ESS score. The concentrations of iron and iron-related proteins and inflammatory cytokines in both cerebrospinal fluid (CSF) and serum were examined.

RESULTS

1. The occurrence rate of EDS in total PD patients was 16.09%. 2. PD-EDS group had significantly severer disease stages, more severe motor and non-motor features of the disease. 3. In CSF, the concentrations of iron and IL-1β in the PD-EDS group were significantly higher and ferritin concentration was prominently lower when compared with the PD-NEDS group and the control group; ESS score was significantly associated with high concentrations of iron and IL-1β and low concentration of ferritin in the PD group. Iron concentration was positively correlated with IL-1β concentration in the PD-EDS group. 4. In serum, no changes were observed in iron and iron-related proteins and inflammatory cytokines among the three groups.

CONCLUSION

EDS was a common symptom in PD patients. PD patients with EDS had more severe motor and some non-motor symptoms. Overloaded iron-relevant inflammation in the brain might be an underlying mechanism of PD-EDS.