Exercise-Induced Oxygen Desaturation and Cognitive Performance in Patients with Parkinson’s Disease: A Prospective Observational Study

Background/Objectives: Respiratory dysfunction in Parkinson’s disease (PD) is frequently underrecognized, particularly when resting oxygen saturation is preserved. Dynamic stress testing, however, may reveal exercise-induced oxygen desaturation, reflecting a latent functional respiratory impairment. The relationship between exertional oxygen desaturation and cognitive performance in PD remains insufficiently explored. Objective: To investigate the association between exercise-induced oxygen desaturation and global cognitive performance in patients with PD, and to explore the contribution of pulmonary gas exchange impairment assessed by diffusing capacity of the lung for carbon monoxide (DLCO). Methods: This prospective, cross-sectional, single-center observational study with consecutive enrollment included 50 patients with idiopathic Parkinson’s disease undergoing multidisciplinary respiratory evaluation following neurological assessment. Participants underwent cognitive evaluation using the Romanian version of the Montreal Cognitive Assessment (MoCA), pulmonary function testing including DLCO and total lung capacity (TLC), and a supervised 6-min walk test (6MWT) with continuous pulse oximetry. Exercise-induced oxygen desaturation was defined as a decrease in SpO2 of ≥4% from baseline. Correlation analyses and multivariable regression models were applied. Results: Exercise-induced oxygen desaturation was frequent, with 60% of patients exhibiting a ≥4% decrease in SpO2 during the 6MWT. Greater desaturation was significantly associated with lower MoCA scores (Spearman’s r = −0.383, p = 0.006). No significant associations were found between exertional desaturation and resting pulmonary function parameters, including DLCO and TLC. In multivariable analysis, lower MoCA score and levodopa–carbidopa intestinal gel treatment independently predicted greater oxygen desaturation during exercise. Conclusions: Exercise-induced oxygen desaturation is common in patients with PD despite preserved resting oxygenation and is associated with poorer cognitive performance. These findings suggest that exertional desaturation may reflect a dynamic functional impairment and may be associated with increased physiological vulnerability. Functional exercise testing with oxygen saturation monitoring may provide complementary information beyond resting pulmonary assessments.