Ventilatory Impairments Associated with Parkinson's Disease: A Systematic Review and Meta-Analysis

Background: The peripheral and central repercussions of Parkinson's disease (PD) affect the neuromuscular system producing a loss of muscle strength that can influence the respiratory system. Although several studies have examined various respiratory aspects of PD, to the best of our knowledge no study to date has systematically reviewed the existing data. Objectives: To examine the available literature related to the respiratory impairment in PD patients. Methods: We used PRISMA guidelines when reporting this review. We searched Pubmed, Cinhal, SciELO, and Cochrane Library, from inception until August 2018. Main variables assessed were forced vital capacity percent predicted (FVC%) and forced expiratory volume in 1 s percent predicted (FEV1%) for PD patients. Results: Six studies were included in this systematic review and meta-analysis. The obtained results concluded that PD patients present poorer pulmonary function when compared to healthy controls. When PD patients were compared between ON and OFF states, the results reviewed are in favour of the ON state. In the meta-analysis performed for FVC% and FEV1%, the results fail to find significant differences between PD patients and controls (p = 0.336 and p = 0.281, respectively), and between PD ON and OFF states (p = 0.109 and p = 0.059, respectively). Conclusions: We conclude that PD patients have impaired respiratory capacities that are related to the PD severity, time since diagnosis, and OFF state. Adequate follow-up of the respiratory function and studies focused on PD phenotypes have to be considered in future studies.