Periodontal inflammatory disease is associated with the risk of Parkinson's disease: a population-based retrospective matched-cohort study.

Background: The cause-effect relation between periodontal inflammatory disease (PID) and Parkinson's disease (PD) remains uncertain. The purpose of our study was to investigate the association between PID and PD.

Methods: We conducted a retrospective matched-cohort study by using Taiwan's National Health Insurance Research Database. We identified 5,396 patients with newly diagnosed PID during 1997-2004 and 10,792 cases without PID by matching sex, age, index of year (occurrence of PID), and comorbidity. Cox proportional hazard regression was used to evaluate the risk of subsequent PD.

Results: At the final follow-up, a total of 176 (3.26%) and 275 (2.55%) individuals developed PD in the case and control groups, respectively. Patients with PID have a higher risk of developing PD (adjusted hazard ratio = 1.431, 95% CI [1.141-1.794],  = 0.002).

Discussion: Our results show that PID is associated with an increased risk of developing PD. Whilst these findings suggest that reducing PID may modify the risk of developing PD, further study will be needed.