Parkinson disease with mild cognitive impairment: Domain-specific cognitive complaints predict dementia

The presence of subjective cognitive complaints (SCC) as a predictor of cognitive impairment in Parkinson´s disease (PD) has shown conflicting results. Most previous studies only assessed complaints in the memory domain. We investigate the association of SCCs across cognitive domains with development of mild cognitive impairment (PD-MCI) and dementia (PDD) in PD and to assess agreement between SCCs and objective cognitive impairments in this population.

This is a retrospective analysis of a prospective cohort study. Participants were enrolled at six North-American movement disorders centers. They underwent neuropsychological and non-cognitive clinical evaluations, including the modified Neurobehavioral Inventory to elicit SCC (rated by each patient and independently by their close contact (CC)). Associations between SCCs and development of future cognitive impairment were assessed. Agreement between SCCs and objective impairment within the same domain was also calculated.

Of 138 included PD patients, 42% fulfilled criteria for PD-MCI. None of the NBI items predicted development of cognitive impairment after one and two years in PD with normal cognition. In PD-MCI patients, SCCs related to attention predicted dementia at year one. CC ratings of SCCs related to memory and language problems predicted PDD in PD-MCI patients. According to CC reported patients' complaints, there was a significant agreement between SCCs and objective cognitive test scores on attention.

Eliciting SCCs including cognitive domains other than memory is crucial for a complete evaluation, including both patient and CC report. Memory, language, and especially attention SCCs in PD-MCI may predict progression to dementia.