Long-term outcome in Parkinson disease: no advantage to initiating therapy with dopamine agonists

This Practice Point commentary discusses long-term follow-up of a treatment intervention study on Parkinson disease (PD). Katzenschlager et al. report on 166 of 302 survivors of a randomized open-label study that compared initial therapy with levodopa, with levodopa plus selegiline, or with bromocriptine, in early untreated PD. The primary study publication, from 1993, suggested that bromocriptine-treated participants were less likely than levodopa-treated participants to develop motor complications during the subsequent 4 years, although levodopa was more effective at relieving symptoms of parkinsonism. The current publication presents data after a median follow-up of 14 years and suggests that protection from motor complications does not persist over the long term. Furthermore, participants who were randomly allocated to initial treatment with levodopa showed better relief of disability and better quality of life over the long term. More than 60% of the original PD cohort had died over the 14-year time interval, underscoring the continued poor prognosis of late-stage PD. The Katzenschlager studies and other recent publications underscore the need to develop newer treatment strategies that consider the multisystem nature of the illness and expand treatment horizons beyond the single neurotransmitter dopamine.