Incidence of muscle relaxant use in relation to diagnosis of Parkinson’s disease

Background Parkinson’s disease is the second most common neurodegenerative disorder. Motor and non-motor symptoms seem to precede the diagnosis of Parkinson’s disease. Objective To evaluate the incidence of muscle relaxant use in community-dwelling persons with and without Parkinson’s disease from 4 years before to 4 years after the diagnosis of Parkinson’s disease. Method Nationwide register-based cohort included all community-dwelling Finnish persons who received reimbursement of Parkinson’s disease drugs between 2000 and 2015 (N = 17,450) and comparison persons without Parkinson’s disease who were matched for age, gender and region of residence (N = 122,694). Data on muscle relaxant use during 1995–2016 were collected from the Prescription Register. Results The incidence of muscle relaxant use was higher among persons with Parkinson’s disease in comparison to persons without Parkinson’s disease from 3 years before the diagnosis until 6 months after the diagnosis. The largest difference in incidence rates was observed at the time of the diagnosis (incidence rate ratio = 2.04, 95% confidence interval = 1.81–2.30). Tizanidine was the most frequently initiated muscle relaxant. Conclusions The incidence of muscle relaxant use starts increasing years before the diagnosis of Parkinson’s disease but declines after that. It is important to identify the causes of muscle symptoms to avoid unnecessary muscle relaxant use and consequent adverse effects and events.