Statin use and the risk of Parkinson's disease in persons with diabetes: A nested case–control study

Aims Persons with diabetes may have an elevated risk of Parkinson's disease (PD). Statin use could also modify the progression of PD. The aim was to study whether there is an association between statin exposure and risk of PD in persons with diabetes. Methods A nationwide, nested case–control study restricted to people with diabetes was performed as part of nationwide register‐based Finnish study on PD (FINPARK). Study included 2017 PD cases and their 7934 matched controls without PD. Persons with PD were diagnosed between 1999 and 2015, and statin use (1995–2015) was determined from Prescription Register. In the main analysis, exposure at least 3 years before outcome was considered. Cumulative exposure was categorized into tertiles, and associations were analysed with conditional logistic regression (adjusted with comorbidities and number of antidiabetic drugs). Results Prevalence of statin use was similar in PD cases and controls, with 54.2% of cases and 54.4% controls exposed before the lag time (adjusted odds ratio [aOR] = 1.03; 95% confidence interval [CI]: 0.92–1.15). Those in the highest cumulative statin exposure tertile had higher risk of PD than statin nonusers (aOR = 1.22; 95% CI: 1.04–1.43), or those in the lowest cumulative statin exposure tertile (aOR = 1.29; 95% CI: 1.07–1.57). Conclusion Our nationwide study that controlled for diabetes duration and used 3‐year lag between exposure and outcome to account for reverse causality does not provide support for the hypothesis that statin use decreases the risk of PD.