Incidence and time trends of drug-induced parkinsonism: A 30-year population-based study

Background: Epidemiological studies of drug-induced parkinsonism remain limited. Objectives: To investigate the incidence and time trends of drug-induced parkinsonism over 30 years in a geographically defined American population. Methods: We used the medical records-linkage system of the Rochester Epidemiology Project to identify all persons in Olmsted County, Minnesota, who received a screening diagnostic code for parkinsonism from 1976 through 2005. A movement disorders specialist reviewed the complete medical records of each person to confirm the presence of drug-induced parkinsonism associated with dopamine-blocking or dopamine-depleting medications. Results: Among 906 incident cases of parkinsonism from 1976 to 2005, 108 persons had drug-induced parkinsonism (11.9%). The average annual incidence rate of drug-induced parkinsonism was 3.3 per 100,000 person-years, was higher in women, and increased with older age. Drug-induced parkinsonism was the fifth-most common type of parkinsonism overall; however, it was the most common type among persons younger than age 40 years. Typical antipsychotic drugs were the most common class of drugs associated with parkinsonism, whereas atypical antipsychotic drugs were rarely involved. The incidence rate of drug-induced parkinsonism decreased 32.0% per decade (relative risk = 0.68; 95% confidence interval: 0.49–0.94) and 68.6% over the 30 years of the study. The decrease was similar in men (65.2%) and women (69.4%); however, the trend was significant only in women. Conclusions: The incidence of drug-induced parkinsonism increased with older age and was higher in women at all ages. Typical antipsychotic drugs were the most common cause. The incidence of drug-induced parkinsonism decreased over the 30 years of the study because of changes in drug use.