Background: C-reactive protein (CRP), a blood inflammatory biomarker, is associated with the development of Alzheimer disease. In animal models of Parkinson disease (PD), systemic inflammatory stimuli can promote neuroinflammation and accelerate dopaminergic neurodegeneration. However, the association between long-term systemic inflammations and neurodegeneration has not been assessed in PD patients.
Objective: To investigate the longitudinal effects of baseline CRP concentrations on motor prognosis in PD.
Design, setting, and participants: Retrospective analysis of 375 patients (mean age, 69.3 years; mean PD duration, 6.6 years). Plasma concentrations of high-sensitivity CRP were measured in the absence of infections, and the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) scores were measured at five follow-up intervals (Days 1-90, 91-270, 271-450, 451-630, and 631-900).
Main outcome measure: Change of UPDRS-III scores from baseline to each of the five follow-up periods.
Results: Change in UPDRS-III scores was significantly greater in PD patients with CRP concentrations ≥0.7 mg/L than in those with CRP concentrations <0.7 mg/L, as determined by a generalized estimation equation model (P = 0.021) for the entire follow-up period and by a generalized regression model (P = 0.030) for the last follow-up interval (Days 631-900). The regression coefficients of baseline CRP for the two periods were 1.41 (95% confidence interval [CI] 0.21-2.61) and 2.62 (95% CI 0.25-4.98), respectively, after adjusting for sex, age, baseline UPDRS-III score, dementia, and incremental L-dopa equivalent dose.
Conclusion: Baseline plasma CRP levels were associated with motor deterioration and predicted motor prognosis in patients with PD. These associations were independent of sex, age, PD severity, dementia, and anti-Parkinsonian agents, suggesting that subclinical systemic inflammations could accelerate neurodegeneration in PD.