Study objectives: Aspiration pneumonia, a leading cause of death in patients with Parkinson disease (PD), usually occurs at the advanced stages of the disease. We investigated both motor and sensory components of cough and induced-sputum substance P (SP) concentrations in patients with early and advanced stages of PD to assess whether cough efficacy is impaired in PD.
Subjects: Fifteen female patients with early stages of PD (Hoehn and Yahr stage II-III), 10 patients with advanced stages of PD (Hoehn and Yahr stage IV), and 15 age-matched female control subjects were investigated.
Measurements: The motor component of cough efficacy was assessed by monitoring voluntary maximal cough peak flow. The sensory component of cough efficacy was assessed by measuring cough reflex sensitivity to citric acid inhalation. Sputum SP concentrations were measured in sputum induced by hypertonic saline solution inhalation.
Results: The mean (± SD) cough peak flow rates in patients with both early PD (230 ± 74 L/min; p < 0.005) and advanced PD (186 ± 60 L/min; p < 0.0001) were significantly weaker than that in control subjects (316 ± 70 L/min). Cough reflex sensitivity in patients with advanced PD (46.7 ± 49.3 g/L) was significantly lower compared to control subjects (14.5 ± 16.6 g/L; p < 0.01) and patients with early PD (11.2 ± 14.8 g/L; p < 0.005). The sputum SP concentration was significantly lower in patients with advanced PD (11.2 ± 8.4 pg/mL) compared to that in control subjects (35.6 ± 15.4 pg/mL) and patients with early PD (28.5 ± 16.4 pg/mL).
Conclusion: In the early stages of the disease, mainly the motor component of cough was impaired. In advanced stages of the disease, both the motor and sensory components of cough were impaired. Sputum SP concentration significantly declined in patients with advanced PD. The results suggest that the combination of impaired motor and sensory components of cough may play an important role in the development of aspiration pneumonia in PD.