- Patients with bipolar disorder were >3 times as likely as individuals in the general population to receive a Parkinson’s disease diagnosis.
Why this matters
- Findings have implications for prognosis and differential diagnosis.
- Diagnosis of bipolar disorder was associated with a sharply elevated likelihood of Parkinson’s disease (OR, 3.35; 95% CI, 2.00-5.60).
- Findings similar in a sensitivity analysis excluding studies having high bias (OR, 3.21; 95% CI, 1.89-5.45).
- In subgroup analysis based on duration of follow-up, Parkinson’s disease risk elevated with:
- Less than 9 years of follow-up (OR, 5.20; 95% CI, 4.26-6.35).
- More than 9 years of follow-up (OR, 1.75; 95% CI, 1.36-2.26).
- However, associations were not significant in subgroups stratified by study design or by diagnostic certainty.
- Systematic review and meta-analysis of 7 retrospective or prospective cohort studies and cross-sectional studies having 4,374,211 total participants: patients with bipolar disorder and controls (general population, hospital population, or US army veterans).
- Main outcome: Parkinson’s disease.
- Funding: None disclosed.
- Possible misdiagnosis of parkinsonism as Parkinson’s disease.
- Residual confounding.
- Heterogeneity of included studies.
- Most did not assess the association as their primary objective.