Progression of parkinsonian signs in Alzheimer's disease

OBJECTIVE: To describe the progression of parkinsonian signs in persons with AD. BACKGROUND: Parkinsonian signs are common in AD and appear to be related to morbidity and mortality. However, little is known about individual patterns of progression of parkinsonian signs. METHODS: A cohort of 410 people with clinically diagnosed AD underwent annual clinical evaluations over a 4-year period, with over 90% of survivors participating in follow-up. The entire motor portion of the Unified Parkinson's Disease Rating Scale (UPDRS) was administered at each evaluation. Previously established measures of four parkinsonian signs were derived from the UPDRS. Scores ranged from 0 to 100 and represented the percent obtained of the total possible item score. RESULTS: A growth curve approach was used to estimate individual paths of change. Rates of change in bradykinesia (4.5% increase per year), rigidity (6.0% increase per year), and gait disorder/postural reflex impairment (8.9% increase per year) were substantial and positively correlated (median r = 0.69). Change in tremor was minimal, mostly confined to postural tremor, and weakly correlated with change in other signs (median r = 0.16). The rate of progression in each sign was highly variable across individuals and not strongly related to demographic factors or use of neuroleptic medications. CONCLUSIONS: Parkinsonian signs other than tremor progress rapidly in AD but at widely differing rates.