Background
Pain is a common symptom of Parkinson's disease (PD). It occurs also as a prodromal sign of PD. It has not yet been described how the use of analgesics changes over time in persons with PD. We investigated the incidence of opioid use from 5 years before to 5 years after PD diagnosis and compared the incidence to a matched cohort.

Methods
This study included 15,763 people diagnosed with incident PD in 2001–2014 and 62,907 matched comparison persons without PD from the Finnish nationwide register-based study on Parkinson's disease (FINPARK). Initiation rates of opioid use during the follow-up were calculated in 6-month time windows, and the difference between persons with and without PD was described using incidence rate ratios (IRRs).

Results
Opioid initiation was more common among persons with PD (37.0%) compared to people without PD (31.2%). The difference between the groups emerged 3 years before the PD diagnosis IRR 1.33 (1.16–1.53), and remained until the end of the follow-up. Mild opioids, such as tramadol and codeine, were the most commonly initiated opioids, and the largest difference in their use was observed 6 months prior to the diagnosis date, while differences in strong opioids emerged after the PD diagnosis. Initiation rates increased over time and remained above those of the comparison group after the PD diagnosis for all opioid classes.

Conclusions
The findings demonstrate the incidence of moderate/severe pain in PD, which requires treatment with opioid-class analgesics. Further studies are needed to understand the long-term impact of opioid use in persons with PD.

Significance Statement
Initiation rate of opioids is increased in persons with Parkinson's disease already at premotor or early motor stage, before the diagnosis is confirmed. Shift towards stronger opioids is observed over the disease progress. Further studies are needed to investigate optimized pain management strategies in Parkinson's disease.