The frequency of parkinsonism in Alzheimer disease (AD) ranges from 11% to 53%,1,2 and the mean number of parkinsonian signs was reported to double during a 12-month period.3 Parkinsonian signs have been consistently associated with greater cognitive deficits,4,5 earlier institutionalization,2,6 and shorter survival.7 One of the limitations to identify parkinsonism in AD is that some of the most common parkinsonian signs (e.g., bradykinesia, masked facies, slow gait), may be confused with symptoms of apathy.8
It is also possible that in AD both parkinsonism and apathy are etiologically related. In cross-sectional studies, we found a strong association between apathy and parkinsonism.8-10 Nevertheless, causality has to be explored in the context of longitudinal studies. Loss of motivation could be an early behavioral expression of a more complex psychomotor syndrome that includes parkinsonism, or alternatively, loss of motivation could be the consequence of increasing motor problems and concomitant functional limitations in AD.
To examine these hypotheses, we assessed a consecutive series of 132 patients with AD who were examined at baseline and between 1 and 4 years later. In a recently published study on this cohort,11 we found that apathy at baseline was a significant predictor of faster cognitive and functional decline, as well as more severe depression. On the other hand, depression at baseline did not predict more severe apathy at follow-up. Based on these findings, we hypothesized that apathy, but not depression, may predict increasing parkinsonism over time among patients with AD.
Autor: Dr. Gustavo Petracca