Objective: The present study cross-sectionally and longitudinally explores the predictive value of subjective cognitive decline (SCD) regarding objective cognitive decline in a large clinical sample of Parkinson’s disease (PD) patients.

Background: 80 percent of PD patients develop cognitive impairment. In some cases, patients report SCD, that is, cognitive deficits that are not objectively measured by neuropsychological testing. While SCD in Alzheimer’s disease (AD) is established as predictor of objective cognitive decline, the role of SCD in preceding objective cognitive deficits in PD is not yet fully understood.

Method: All data was drawn from the LANDSCAPE/DEMPARK study. The sample consists of 382 patients at baseline (267 male and 115 female, 190 cognitively normal (PD-NC) and 192 mildly impaired (PD-MCI)). Cognitive performance and mental state were assessed via a neuropsychological test battery and psychometric measures. SCD was assessed via a standardized semi-structured interview as well as supplemental criteria. Based on existing research, we constructed two continuous indices to capture SCD variance: the SCD-C consisting of subjective decline in relevant cognitive areas and the SCDplus consisting of worrying, executive functioning as SCD domain, SCD onset and PD onset. Cross-validated mixed models with random intercepts were calculated for PD-NC and PD-MCI patients separately with mean squared error (MSE) between estimated and observed cognition as measure for fit, with lower MSE signifying better fit between estimated and observed cognition.

Results: In PD-NC patients excluding SCDplus and SCD-C scores yields the best results in terms of predictive performance (MSE = 5.277).  Hence, no predictive influence of SCD was found within that group. In MCI patients, including SCDplus as cross-sectional predictor improves the predictive performance and leads to the best results (MSE = 12.129) compared to a model without SCD (MSE = 12.797), while SCD-C worsens fit (MSE = 13.441), indicating that SCDplus might be a valid predictor for objective cognition in that group of patients.

Conclusion: While we find the SCDplus criteria to be predictive of objective cognitive decline in PD-MCI patients, the present results indicate a complex relation between objective and subjective cognition in PD that may differ from AD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/subjective-cognitive-decline-as-predictor-of-objective-cognitive-decline-in-parkinsons-patients/