Comparative risk of Parkinsonism associated with olanzapine, risperidone and quetiapine in older adults-a propensity score matched cohort study

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.