Initial motor reserve and long-term prognosis in Parkinson's disease

There are individual differences in motor deficits, despite a similar degree of dopamine neuronal loss in Parkinson's disease (PD), called motor reserve (MR). Factors enhancing MR have been documented previously, but the influence of initial MR on the long-term prognosis remains unclear. In this longitudinal study, we enrolled 205 patients with de novo PD to estimate individual MR based on initial motor deficits and striatal dopamine depletion using the residual-based approach. We assessed the risk of developing levodopa-induced dyskinesia (LID) or freezing of gait (FOG) and longitudinal increases in levodopa-equivalent dose (LED) according to MR estimates using the Cox regression model and linear mixed model, respectively. Throughout the follow-up period (≥3 years), greater MR estimates were associated with a lower risk for LID and FOG. In addition, patients with high MR received lower LED than those with low MR. These findings suggest that the initial MR, that is, individual's capacity to cope with PD-related pathologies, can be maintained with disease progression and can modulate the risk for LID or FOG.