Impaired Respiratory Function as an Auxiliary Marker for Disease Progression in Different Motor Subtypes of Parkinson's Disease.

BACKGROUND

The mechanisms underlying respiratory function impairments in different motor subtypes of Parkinson's disease (PD) remain poorly understood.

OBJECTIVES

This study aims to elucidate the differences in respiratory function between the two main PD motor subtypes, tremor-dominant (TD) and postural instability gait difficulty (PIGD), and investigate their associations with disease severity.

METHODS

A total of 106 PD patients (59 TD and 47 PIGD) and 42 age- and sex-matched healthy controls (HCs) were enrolled. Pulmonary function tests (PFTs), respiratory muscle strength, and respiratory drive measurements were conducted. Multivariate models were employed to analyze correlations between respiratory function indices and clinical characteristics.

RESULTS

Compared to HCs, PIGD patients exhibited significant reductions in forced vital capacity (FVC%) (P = 0.018), peak expiratory flow (PEF%) (P < 0.001), diffusing capacity for carbon monoxide adjusted for hemoglobin (DLCOc%) (P = 0.013), and total lung capacity (TLC%) (P = 0.045). Although differences between the two motor subtypes were not statistically significant, a more apparent declining trend was observed in PIGD patients. Regarding respiratory muscle strength, PIGD patients showed more severe impairments in maximal inspiratory pressure (PImax%) (P < 0.001) and maximal expiratory pressure (PEmax%) (P < 0.001). Multivariate linear regression analysis confirmed that PEF% was a significant determinant of cognitive function in TD patients (β = 0.497, P < 0.001), whereas the airway occlusion pressure at 100 milliseconds (P0.1%) influenced cognitive levels in PIGD patients (β = -0.373, P = 0.015).

CONCLUSIONS

Compared to TD patients, PIGD patients have more pronounced respiratory impairments. Specific respiratory indices correlate with motor severity and cognitive decline, highlighting their potential as markers for disease progression in PD motor subtypes.