Urate as a predictor of the rate of clinical decline in Parkinson disease

Abstract

Background: The risk of Parkinson disease (PD) and its rate of progression may decline with increasing concentration of blood urate, a major antioxidant.

Objective: To determine whether serum and cerebrospinal fluid concentrations of urate predict clinical progression in patients with PD.

Design, setting, and participants: Eight hundred subjects with early PD enrolled in the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) trial. The pretreatment urate concentration was measured in serum for 774 subjects and in cerebrospinal fluid for 713 subjects.

Main outcome measures: Treatment-, age-, and sex-adjusted hazard ratios (HRs) for clinical disability requiring levodopa therapy, the prespecified primary end point of the original DATATOP trial.

Results: The HR of progressing to the primary end point decreased with increasing serum urate concentrations (HR for highest vs lowest quintile = 0.64; 95% confidence interval [CI], 0.44-0.94; HR for a 1-SD increase = 0.82; 95% CI, 0.73-0.93). In analyses stratified by alpha-tocopherol treatment (2000 IU/d), a decrease in the HR for the primary end point was seen only among subjects not treated with alpha-tocopherol (HR for a 1-SD increase = 0.75; 95% CI, 0.62-0.89; vs HR for those treated = 0.90; 95% CI, 0.75-1.08). Results were similar for the rate of change in the Unified Parkinson's Disease Rating Scale score. Cerebrospinal fluid urate concentration was also inversely related to both the primary end point (HR for highest vs lowest quintile = 0.65; 95% CI, 0.44-0.96; HR for a 1-SD increase = 0.89; 95% CI, 0.79-1.02) and the rate of change in the Unified Parkinson's Disease Rating Scale score. As with serum urate concentration, these associations were present only among subjects not treated with alpha-tocopherol.

Conclusions: Higher serum and cerebrospinal fluid urate concentrations at baseline were associated with slower rates of clinical decline. The findings strengthen the link between urate concentration and PD and the rationale for considering central nervous system urate concentration elevation as a potential strategy to slow PD progression.

Figure 1.A. Hazard ratio (HR) for reaching endpoint according to assignment to α-tocopherol (vitamin E) and quintile of baseline serum urate

(referenced to placebo-treated subjects in the lowest quintile). Bars indicate 95% confidence intervals for HRs, adjusted for age, gender, and treatment group (deprenyl or placebo)

Figure 1.B. Hazard ratio (HR) for reaching endpoint according to assignment to α-tocopherol (vitamin E) and quintile of baseline CSF urate

(referenced to placebo-treated subjects in the lowest quintile). Bars indicate 95% confidence intervals for HRs, adjusted for age, gender, and treatment group (deprenyl or placebo)

Figure 2.A. Annualized rate of UPDRS change according to assignment to α-tocopherol (vitamin E) and quintile of baseline serum urate

Bars indicate standard errors of the mean, Adjusted for age, gender, and treatment group (deprenyl or placebo) Significantly different from lowest quintile of urate placebo-treated group: *p<0.05; **p<0.01; ***p<0.001

Figure 2.B. Annualized rate of UPDRS change according to assignment to α-tocopherol (vitamin E) and quintile of baseline CSF urate

Bars indicate standard errors of the mean, Adjusted for age, gender, and treatment group (deprenyl or placebo). Significantly different from lowest quintile of urate placebo-treated group: *p<0.05; **p<0.01