This study, called a systematic review and meta-analysis, combined the results of seven studies with 4.3 million participants to examine a potential association between bipolar disorder with a later diagnosis of Parkinson disease of unknown cause.
A sensitivity analysis was performed by removing the studies that had a high risk of bias and also showed an increased risk of PD in people with BD. Preplanned subgroup analyses according to study design and diagnostic certainty failed to show a significant effect.
The findings suggest that a previous diagnosis of bipolar disorder was associated with increased likelihood of a subsequent Parkinson disease diagnosis but subgroup analyses suggest the possibility of an overestimation of the magnitude of the associations.
The main limitation of the study is analysis that suggests a greater likelihood of a Parkinson disease diagnosis in shorter studies which raises concerns over misdiagnosis. These findings highlight the probability that BD may be associated with a later development of PD and the importance of the differential diagnosis of parkinsonism features in people with BD.
Is bipolar disorder associated with increased risk of Parkinson's disease?
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