Olfactory function deteriorates in patients with Parkinson's disease complicated with REM sleep behavior disorder

Area of Science:

• Neurology
• Sleep Medicine
• Neuroscience

Background:

• The relationship between olfactory dysfunction, REM sleep behavior disorder (RBD), and cognitive function in Parkinson's disease (PD) remains unclear.
• This study aimed to clarify the impact of these symptoms on PD patients.

Purpose of the Study:

• To evaluate the association between olfactory dysfunction, RBD, and cognitive impairment in Parkinson's disease.
• To investigate the correlation between olfactory test scores, RBD status, and cognitive assessment results in PD patients.

Main Methods:

• 62 Parkinson's disease patients underwent olfactory testing (OSIT-J) and polysomnography (PSG).
• Patients were categorized into three groups: PD with clinical RBD, PD with subclinical RBD, and PD with normal REM sleep.
• Cognitive functions were assessed using the Montreal Cognitive Assessment Japanese version (MoCA-J), alongside autonomic function tests.

Main Results:

• Significant differences in olfactory, autonomic, and cognitive functions were observed across the three groups.
• Patients with PD and clinical RBD showed significantly poorer olfactory function (OSIT-J scores) compared to those with normal REM sleep.
• Olfactory dysfunction was strongly associated with RBD and correlated with lower MoCA-J scores, indicating cognitive impairment.

Conclusions:

• Olfactory dysfunction is significantly associated with REM sleep behavior disorder in Parkinson's disease patients.
• Screening for olfactory dysfunction is vital in PD patients with RBD due to its link with cognitive impairment.