The natural history of LDR and SDR with disease progression in Kempster’s cohort. From Alty et al., Longitudinal study of the levodopa motor response in Parkinson’s disease: relationship between cognitive decline and motor function, Mov Disord, 2009, Figure 5.19 Modified Webster Scores of PD patients in the practical “off” state (tops of boxes) and 60–90 minutes after their usual levodopa dose (bottom of boxes) as a function of disease duration for non-demented (black boxes) and demented (MMSE < 24, white boxes) patients. The Modified Webster Score is a standardized assessment of motor function, with higher scores indicating worse function. Note the diminished magnitude of the SDR in demented vs non-demented patients.