The Evolution of Disability in Parkinson Disease

The objectives of this study are to assess the level of disease severity associated with disability in Parkinson disease (PD) and the sequence of loss of independence in basic and instrumental activities of daily living (ADLs and IADLs). Six hundred eighteen patients with PD were evaluated for disease severity with the Unified PD Rating Scale (UPDRS) and for disability with the Older Americans Resource and Services Disability Subscale (OARS). The association between patient-reported disability on ADLs and IADLs and level of disease severity on the total UPDRS was examined cross-sectionally. Disability, with loss of independent function is reported between total UPDRS scores 30 to 40, and HY stages II to III. Difficulty with daily activities, without loss of independent function is reported earlier, at UPDRS <20 and HY I to II. Difficulty with walking is initially reported, followed by problems with a number of gait-dependent activities including housework, dressing, transferring in and out of bed, and traveling in the community. The transition from HY stage II to III marks a pivotal milestone in PD, when gait and balance impairment results in disability in many gait-dependent activities. The onset of disability in PD can be identified by asking patients about their walking, housework, dressing, and traveling. While individual patients vary in progression, the benchmarks of disability in this study provide guidance when counseling patients about prognosis. Better understanding of the stages of disability may facilitate the development of novel outcome measures in clinical trials in PD.