Abstract
Purpose
The purpose of this study was to examine the incidence of Parkinsonism in new users of second‐generation antipsychotics (SGAs) in older adults (≥65 years). In the secondary analyses, we examined the risk of Parkinsonism by type and dose of SGA and conducted age‐sex interactions.
Method
This population‐based study included older adults who had a new‐onset diagnosis of Parkinsonism and who started taking olanzapine, risperidone or quetiapine between 1 January 2005, and 30 December 2016. The Cox proportional hazard (COXPH) model with inverse probability treatment weighted (IPTW) covariates was used to evaluate the risk of new‐onset Parkinsonism associated with SGAs, using quetiapine as the reference. We used the Generalized Propensity Score method to evaluate the dose‐response risk of Parkinsonism associated with SGAs.
Results
After IPTW adjustment for covariates, the COXPH model showed that compared to quetiapine, the use of olanzapine and risperidone were associated with an increased risk of Parkinsonism. The IPTW‐hazard ratios are 1.76 (95% confidence interval 1.57‐1.97) and 1.31 (95%CI 1.16‐1.49), respectively. The dose‐response risk of Parkinsonism was highest for olanzapine with a hazard ratio of 1.69 (95%CI 1.40‐2.05) and the least for quetiapine with a hazard ratio of 1.22 (95%CI 1.14‐1.31). The risk of Parkinsonism in the 65 to 74‐year age group was higher for both sexes with risperidone compared to olanzapine, but the risk increased with olanzapine for both sexes in the 85+ age group.
Conclusion
The study found that the risk of new‐onset Parkinsonism in older adults is 31% and 76% higher with risperidone and olanzapine respectively compared to quetiapine.