Association between strength, clinical status and functional capacity in Parkinson's disease

Abstract

Introduction: Parkinson’s disease (PD) is considered one of the most common neurodegenerative diseases nowadays. Its incidence is larger in elders and men, presenting high levels of prevalence. This disease compromises the nuclear basis of brain structure due to the loss of dopaminergic neurons in the substantia nigra, causing motor and non-motor symptoms. PD has a multifactorial etiology, and endogenous and exogenous factors are used to explain its occurrence. Quadriceps muscle strength in a parkinsonian patient is minor than in a healthy person at the same age, which suggests decreases in balance and increase in the risk of falls. Also, the muscle strength seems to be associated with severity of PD and quality of life in PD patients. Objective: To investigate the association between the quadriceps muscle strength and body balance, clinical status and quality of life in PD patients. Methods: To achieve this goal, 25 individuals were analyzed (18 men), with age: median (med) = 66 years, first quartile (Q1) = 62.50 years, third quartile (Q3) = 71 years; height: med = 168 cm, Q1 = 162 cm, Q3 = 171 cm; and weight: med = 77 kg, Q1 = 68 kg, Q3 = 84.50 kg. The participant’s signs and symptoms were assessed using the Unified Parkinson's disease rating scale (UPDRS). Strength of the knee extensors was measured during a maximal isometric voluntary contraction (MVC) of the quadriceps muscle. Quality of life (QOL) was evaluated using the Parkinson’s Disease Questionnaire (PDQ-39) and balance was accessed: Timed get up and go test (TUG), Dynamic Gait Index (DGI) and Mini Balance Evaluation Systems Test (Mini BESTest) scales. Results: Participants presented sufficient scores to a good balance, except in DGI. Associations were found between TMT and MBT and strength (rho = 0.528, 0.484); between clinical status and strength (rho = -0.610 a -0.577), and between strength and PDQ-39 (rho = 0.455). Conclusion: The results suggested that as greater the muscle function of quadriceps better the balance and QOL, and smaller is the PD severity during the ON period (decreasing motor symptoms). The balance tests have different features and it is necessary to choose with caution according to the objective and the evaluated individual. Future longitudinal controlled trials should be performed to investigate a causal relationship between these variables.