Reduced dopamine transporter binding predicts early transition to Lewy body disease in Japanese patients with idiopathic rapid eye movement sleep behavior disorder

Purpose: We examined dopamine transporter (DAT) binding in Japanese patients with idiopathic rapid eye movement sleep behavior disorder (IRBD) as a biomarker for the development of Lewy body disease (LBD). Methods: [I-123]FP-CIT SPECT (DAT-SPECT) scans of 74 IRBD patients were compared to those from healthy Japanese subjects, and the predictive value for conversion to LBD during a 5-year follow-up was evaluated. Results: Baseline DAT deficits (Z-score <= -2.5) were observed in 25 (33.8%) of the IRBD patients. During follow-up, 25 patients (33.8%) developed LBD [19 Parkinson's disease and 6 dementia with Lewy bodies], with a mean latency of 2.4 +/- 1.6 years from imaging. The receiver operating characteristics curve revealed that the Z-score of baseline DAT binding in the striatum of abnormal DAT-SPECT patients who later developed LBD differed from those who remained disease-free. Kaplan-Meier survival analysis showed an increased risk of LBD in patients with a Z-score <= -2.5 for DAT binding in the striatum of abnormal DAT-SPECT patients compared to patients with a Z-score > -2.5. Conclusions: DAT-SPECT identifies IRBD patients at short-term risk for developing LBD. Decreased DAT binding in the striatum (Z-score <= -2.5) predicts development of LBD within 5 years, and may be useful in future disease-prevention trials in IRBD patients.