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TOPLINE:

Schizophrenia was associated with a threefold increased risk for Parkinson’s disease (PD), with the risk varying by the type of antipsychotic medications used, new research showed.

METHODOLOGY:

• Investigators conducted a retrospective cohort study using records of more than 42,500 adults with schizophrenia (mean age, 66 years; 61% female) from the National Health Insurance Service database of South Korea from 2010 to 2021.
• These patients were propensity score-matched (1:2) with 85,041 control individuals without schizophrenia based on the Charlson comorbidity index score, age, sex, and index year.
• The primary outcome was incident PD, defined as new diagnoses occurring at least 1 year after the initial diagnosis of schizophrenia, requiring at least one inpatient or two outpatient diagnoses within a 1-year period.
• Investigators also examined the relationship between the use of commonly prescribed antipsychotic medications at the time of schizophrenia diagnosis and the subsequent development of PD.

TAKEAWAY:

• Patients with schizophrenia had a significantly elevated risk for PD compared with matched control individuals (adjusted hazard ratio [aHR], 3.20; P < .001).
• The use of antipsychotic medications was significantly associated with the development of PD (aHR, 1.08; P = .0045). Among antipsychotic medications, the use of risperidone was associated with an increased risk for PD compared with nonuse (aHR, 1.20; P < .001), whereas the use of quetiapine was associated with a reduced risk compared with nonuse (aHR, 0.95; P = .0317).
• Among patients prescribed any antipsychotic, comorbidities that were most strongly associated with an increased risk for PD included neurotic, stress-related, and somatoform disorders (HR, 1.380; P < .001) and mental and behavioral disorders due to the use of psychoactive substances (HR, 1.258; P < .001).
• At 10 years, the rate of PD-free survival of patients with schizophrenia was significantly lower than that of control individuals (P < .0001).

IN PRACTICE:

“Our study highlights the elevated risk of PD in individuals with schizophrenia, empha­sizing the need for close monitoring of this patient population,” the investigators of the study wrote. “The impact of antipsychotic medications, particularly risperidone and quetiapine, on the development of PD warrants further investigation to better understand the long-term effects of these treatments,” they added.

SOURCE:

The study was led by Jin Yeon Gil, College of Pharmacy, Chungbuk National University, Cheongju-si, South Korea. It was published online on May 4 in PLoS One.

LIMITATIONS:

The retrospective observational design of the study, the absence of laboratory test results, restricted access to granular clinical information including severity of disease and timing of onset of symptoms, potential misclassification of diagnoses based on administrative codes, no direct assessment of medication adherence, and the risk for reverse causation were some of the limitations. Additionally, the close association between the diagnosis of schizophrenia and the use of antipsychotics and time-varying treatment patterns such as medication switching may have caused residual and misclassification biases.

DISCLOSURES:

No specific funding was received for the study. The investigators reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.