Excessive Iron and α-Synuclein Oligomer in Brain are Relevant to Pure Apathy in Parkinson Disease

To investigate the demographic features, clinical features, and potential mechanism in patients with Parkinson disease (PD) with pure apathy.

A total of 145 patients with PD without depression and dementia and 30 age-matched controls were consecutively recruited. Patients with PD were evaluated by Apathy Scale (AS), scales for motor symptoms and quality of life. The levels of iron, oxidative and neuroinflammatory factors, α-synuclein oligomer, and dopamine in cerebrospinal fluid (CSF) from patients with PD and controls were detected by enzyme-linked immunosorbent assay, chemical colorimetric method, and high-performance liquid chromatography. Comparisons between PD with pure apathy and with no pure apathy groups and correlation between AS score and the levels of above factors were analyzed.

There were 64 (44.14%) cases in PD-apathy group. The PD-apathy group had older age, (97.81 ± 10.82) years versus (61.86 ± 10.80) years, and severer quality of life (P < .05). The PD-apathy and PD without apathy groups presented no remarkable differences in motor symptoms (P > .05). The levels of iron, hydroxyl radical (·OH), hydrogen peroxide (H2O2), and α-synuclein oligomer in CSF in PD-apathy group were significantly higher than that in PD without the apathy group (P < .05). In patients with PD, the AS score was positively correlated with the levels of iron, ·OH, H2O2 and α-synuclein oligomer in CSF (r = 19.838, .063, 1.046, and 0.498, respectively, P < .05). In PD-apathy group, iron level was positively correlated with ·OH level (r = .011, P < .05), and H2O2 level was positively correlated with α-synuclein oligomer level in CSF (r = .045, P < .05).

Patients with PD had high prevalence of pure apathy. Patients with PD having pure apathy had older age. Pure apathy reduced quality of life for patients without worsening motor function. Excessive iron and α-synuclein oligomer in brain commonly contributed to pure apathy of PD through potential mechanism of oxidative stress.