Objective: To compare motor severity between individuals with drug-induced Parkinsonism (DIP) and idiopathic Parkinson’s disease (iPD)

Background: DIP and iPD may present with similar motor impairments, including bradykinesia, tremor, rigidity, and postural instability. However, a key differentiating factor between the two conditions is presynaptic dopaminergic integrity. In DIP, nigrostriatal neurons remain preserved, whereas in iPD, they undergo progressive degeneration. These pathophysiological differences may lead to differences in motor severity between the conditions

Method: A systematic review was conducted using EMBASE, PEDro, PsycINFO, PubMed, Scopus, and Web of Science. The study followed the PRISMA guidelines. We included studies comparing participants diagnosed with DIP and iPD. Studies were excluded when analyses combined DIP or iPD with other neurological or psychiatric conditions. Motor severity was compared between groups using baseline UPDRS Part III scores, with participants matched according to Hoehn & Yahr stage. A random-effects meta-analysis was performed using the restricted maximum likelihood (REML) estimator. Mean differences (MD) with 95% confidence intervals were calculated to assess differences in UPDRS Part III scores between groups. Between-study heterogeneity was evaluated using the I² statistic and τ²

Results: A total of 30,584 records were retrieved from the databases. Two independent reviewers determined that 23 studies met the inclusion criteria, comprising 2,629 participants. The document screening process is shown in Figure 1, and the global distribution of included studies is illustrated in Figure 2. Of these, 11 studies were included in the meta-analysis, totaling 816 participants: 297 in the DIP group and 519 in the iPD group. The meta-analysis showed no difference in motor severity between the groups (MD = −0.85 points; 95% CI −4.89 to 3.18). High heterogeneity was observed among studies (I² = 84.2%; τ² = 29.86), indicating substantial variability across the included samples (Figure 3)

Conclusion: No consistent differences in motor severity were observed between DIP and iPD. However, the high heterogeneity and the influence of individual studies indicate that potential clinical differences may depend on population characteristics, such as symptom severity, diagnostic criteria, and the offending drug

Flowchart of the study selection procedure

The global distribution of included studies.

Forest plot comparing motor severity in DIP vs iPD

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MDS Abstracts - https://www.mdsabstracts.org/abstract/comparison-of-motor-severity-in-individuals-with-drug-induced-parkinsonism-and-idiopathic-parkinsons-disease-a-systematic-review-and-meta-analysis/