Study objective: The association between restless legs syndrome (RLS) and Parkinson disease has been extensively studied, but the temporal relationship between the two remains unclear. We thus conduct the first prospective study to examine the risk of developing Parkinson disease in RLS.
Design: Prospective study from 2002-2010.
Setting: United States.
Participants: There were 22,999 US male health professionals age 40-75 y enrolled in the Health Professionals Follow-up Study without Parkinson disease, arthritis, or diabetes mellitus at baseline.
Measurement and results: RLS was assessed in 2002 using a set of standardized questions recommended by the International RLS Study Group. Incident Parkinson disease was identified by biennial questionnaires and then confirmed by review of participants' medical records by a movement disorder specialist. We documented 200 incident Parkinson disease cases during 8 y of follow-up. Compared to men without RLS, men with RLS symptoms who had symptoms greater than 15 times/mo had higher risk of Parkinson disease development (adjusted relative risk = 1.47; 95% confidence interval: 0.59, 3.65; P = 0.41). This was statistically significant only for cases diagnosed within 4 y of follow-up (adjusted relative risk = 2.77; 95% confidence interval: 1.08, 7.11; P = 0.03).
Conclusion: Severe restless legs syndrome may be an early feature of Parkinson disease.
Keywords: Parkinson disease; Restless legs syndrome; prospective study.