Elevated homocysteine levels in levodopa‐treated idiopathic P arkinson's disease: a meta‐analysis

To assess the association between the elevation of plasma homocysteine ( H cy) level and long‐term levodopa ( L ‐dopa) therapy in idiopathic P arkinson's disease ( PD ). We performed a systematic literature review to recruit original studies published up to M ay 14, 2012. Studies enrolled should be controlled, with specific information of long‐term L ‐dopa application and plasma H cy in patients with PD . Effects were summarized using standardized mean differences ( SMD s) or weighted mean differences ( WMD s). Our search enrolled 22 eligible studies. Plasma H cy levels were significantly higher in L ‐dopa‐treated patients than those in healthy controls [ SMD 0.97; 95% confidence interval ( CI ) 0.80–1.14, P  < 0.001], L ‐dopa‐naïve patients with PD ( SMD 0.99; 95% CI 0.54–1.44, P  < 0.001), and untreated patients ( SMD 0.52; 95% CI 0.18–0.86, P  < 0.01). However, its levels in untreated patients with PD were not significantly higher than in healthy controls ( SMD 0.24; 95% CI −0.03 to 0.51, P  > 0.05). Patients with PD treated with L ‐dopa plus catechol‐ O ‐methyltransferase inhibitor ( COMT ‐ I ) showed lower plasma H cy concentrations compared with L ‐dopa‐treated patients ( WMD 4.62; 95% CI 2.89–6.35, P  < 0.001). L ‐dopa treatment is associated with the increase in plasma H cy level in patients with PD . COMT ‐ I may attenuate L ‐dopa‐induced elevation of H cy level.