Prevalence of sarcopenia in Parkinson's disease: A systematic review and meta-analysis

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder characterized by the death of dopaminergic neurons in the substantia nigra (SN).1,2 Overall, PD's prevalence increases with age. The prevalence rate is 41 per 100,000 within individuals aged 40–49 years, 107 per 100,000 within 50–59 years, 173 per 100,000 within 55–64 years, 428 per 100,000 within 60–69 years, 1087 per 100,000 within 70–79 years,3 and there is 1.5 to 2 higher incidence of PD in males than in females.4,5

The diagnosis of PD is essentially clinical,6,7 through the identification of motor disorders such as resting tremor, bradykinesia, rigidity, and postural instability.8 In addition, secondary symptoms may also be present, such as olfactory dysfunction, depression, sleep disorder, cognitive decline, hyponymy, dysarthria, sialorrhea, micrography, freezing festination,9 dystonia, and dysphagia.10 Disease progression is evaluated by motor impairment and postural instability, from unilateral and bilateral inability to ambulate, until bed restriction that is usually assessed by Hohen and Yahr scale (H&Y).11, 12, 13

PD progression leads to reduced motor capacity, changes in body composition, decreased physical performance, and an impact on vitality.14 These factors have also been observed in sarcopenia following aging.15 According to the latest review by the European Working Group on Sarcopenia in Older Persons (EWGSOP) performed in 2018, sarcopenia is characterized by a reduction in muscle mass and consequent loss of strength.15 The causes of sarcopenia are multifactorial, and the normal aging process increases the risk of sarcopenia.15 The prevalence of sarcopenia is approximately 20% in individuals over 70 years of age, while this percentage increases to 50% in people over 80 years of age.16 The factors that cause sarcopenia are diverse, and include aging, cognitive decline, lung, cardiac and neurodegenerative diseases.17

The prevalence of sarcopenia combined with PD is controversial, varying from 17.2 to 55.7%.18, 19, 20, 21, 22 The main reason for this discrepancy might be linked to the different patients’ age in previous studies. A previous systematic review and meta-analysis reported high heterogeneity among studies that evaluated sarcopenia in PD.23 These authors verified that the prevalence of sarcopenia in PD was 29%, although this percentage dropped to 17% when only considering studies with a low risk of bias.23 Nevertheless, meta-analyses performed by these authors did not consider age as a confounding variable.

Considering that PD preferentially affects older adults,3,24 it is crucial to develop strategies to meet their needs and provide care strategies of individuals with the disease.4 However, it is not clear whether the high incidence of sarcopenia among PD patients is caused by the neurodegenerative process, or due to aging which is coincidently more evident as PD aggravates.1,2

Therefore, our main goal was to determine the prevalence of sarcopenia in patients with PD compared to healthy participants through a meta-analysis of previous studies in the literature. The secondary aim was to analyze the effect of age, the instruments used to identify sarcopenia, and confounding factors such as sex and disease progression, on the prevalence of sarcopenia in PD patients.

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