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Abstract
Objective Given the limited information on cognitive function before Parkinson disease (PD) clinical onset in the general population, we sought to assess prodromal PD (pPD) probability and relate it to detailed cognitive performance in a community cohort.
Methods In a population-based cohort of 1,629 dementia-free and PD-free participants ≥65 years of age in Greece, we assessed probability of pPD according to the International Parkinson and Movement Disorder Society's criteria. Clinical cognitive diagnoses (cognitively unimpaired, mild cognitive impairment [MCI], dementia) considering neuropsychological testing and functional status were assigned in consensus conferences. Cognitive performance in 5 cognitive domains was assessed by a detailed neuropsychological battery and summarized in the form of z scores. We investigated associations between pPD probability (and its individual constituents) and cognitive outcomes.
Results The median probability of pPD was 1.81% (0.2%–96.7%). Participants with MCI had higher probability of pPD compared to those with normal cognition (p < 0.001). Higher probability of pPD was related to lower performance in all cognitive domains (memory, language, executive, attention, and visuospatial function) (p < 0.001). Lower cognitive performance was further associated with certain nonmotor markers of pPD, such as daytime somnolence, depression, urinary dysfunction, constipation, and subthreshold parkinsonism (p < 0.001).
Conclusions Higher probability of pPD was associated with lower cognitive performance in all domains and higher probability of MCI. This may reflect a widespread pathologic process although future studies are warranted to infer causality. These results suggest to clinicians that they should assess cognition early, and to researchers that they should further look into the possible mechanisms that may underlie this observation.
Glossary
- CI=
- confidence interval;
- DSM-IV-TR=
- Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision;
- HAAS=
- Honolulu–Asia Aging Study;
- HELIAD=
- Hellenic Longitudinal Investigation of Aging and Diet;
- LR=
- likelihood ratio;
- MCI=
- mild cognitive impairment;
- MDS=
- International Parkinson and Movement Disorder Society;
- OR=
- odds ratio;
- PD=
- Parkinson disease;
- pPD=
- prodromal Parkinson disease;
- PRIPS=
- Prospective Evaluation of Risk Factors for Idiopathic Parkinson's Syndrome;
- RBD=
- REM sleep behavior disorder;
- ROS=
- Religious Orders Study;
- SES=
- socioeconomic status;
- UPDRS=
- Unified Parkinson's Disease Rating Scale
Footnotes
Go to Neurology.org/N for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received September 13, 2018.
- Accepted in final form January 11, 2019.
- © 2019 American Academy of Neurology
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