Abstract
Over the course of the disease, about 80% of Parkinson’s disease patients will develop cognitive impairment. However, predictive factors associated with cognitive decline are still under investigation. Here, we investigated which clinically available markers are predictive of cognitive impairment in a cohort of early drug-naïve Parkinson’s disease patients. 294 drug-naïve Parkinson’s disease patients, who were cognitively normal at baseline, were recruited from the Parkinson’s Progression Markers Initiative. At 36-month follow-up, patients were diagnosed with cognitive impairment according to two levels: Level 1 diagnosis was defined as MoCA < 26 and Level 2 diagnosis was defined as MoCA < 26, alongside an impaired score on at least two neuropsychological tests. Predictive variables with a validated cut-off were divided into normal or abnormal measures, whilst others were divided into normal or abnormal measures based on the decile with the highest power of prediction. At 3 years’ follow-up, 122/294 Parkinson’s disease (41.5%) patients had cognitive decline. We found that age at Parkinson’s disease onset, MDS-UPDRS Part-III, Hopkin’s Learning Verbal Test-Revised Recall, Semantic Fluency Test and Symbol Digit Modalities Test were all predictors of cognitive decline. Specifically, age at Parkinson’s disease onset, Semantic Fluency Test and symbol Digit Modalities Test were predictors of cognitive decline defined by Level 2. The combination of three abnormal tests, identified as the most significant predictors of cognitive decline, gave a 63.6–86.7% risk of developing cognitive impairment defined by Level 2 and Level 1 criteria, respectively, at 36-month follow-up. Our findings show that these clinically available measures encompass the ability to identify drug-naïve Parkinson’s disease patients with the highest risk of developing cognitive impairment at the earliest stages. Therefore, by implementing this in a clinical setting, we can better monitor and manage patients who are at risk of cognitive decline.
Highlights
Cognitive impairment (CI) is currently considered to be one of the most common non-motor aspects of Parkinson’s disease (PD), which greatly affects quality of life (Schrag et al 2017), increases caregiver burden and nursing home placement (Aarsland et al 2005)
Backward elimination regression analysis for cognitive decline defined by Level 1 revealed the following predictors: age of onset [hazard ratio (HR) 1.03, 95% confidence interval (CI) 1.01–1.06; Wald 6.75 P = 0.009], MDS-UPDRS Part-III (HR 1.03, 95% CI 1.00–1.05; Wald 5.20; P = 0.023), Semantic Fluency Test (HR 0.98, 95% CI 0.96–1.00; Wald 4.03; P = 0.045), Symbol Digit Modalities Test (HR 0.98, 95% CI 0.95–0.99; Wald 4.18; P = 0.041), Hopkin’s Learning Verbal Test-Revised Recall (HR 0.972, 95% CI 0.954–0.991; Wald: 8.18 P = 0.004) and Montreal Cognitive Assessment (MoCA) (HR 0.81, 95% CI 0.70–0.95; Wald 7.00; P = 0.008)
Backward elimination regression analysis for cognitive decline defined by Level 2 indicated the following predictors (Table 2): age (HR 0.48, 95% CI 0.24–0.98; Wald 4.12; P = 0.042), age of onset (HR 2.24, 95% CI 1.09–4.58; Wald 4.84; P = 0.028), MDS-UPDRS Part-III (HR 1.06, 95% CI 1.02–1.10; Wald 7.36; P = 0.007), Semantic Fluency Test (HR 0.95, 95% CI 0.92–0.99; Wald 8.12; P = 0.004), Symbol Digit Modalities Test (HR 0.93, 95% CI 0.89–0.97; Wald 12.97; P = 0.0003) and Benton Judgement of Line Orientation (HR 0.82, 95% CI 0.71–0.94; Wald 7.96; P = 0.005)
Summary
Cognitive impairment (CI) is currently considered to be one of the most common non-motor aspects of Parkinson’s disease (PD), which greatly affects quality of life (Schrag et al 2017), increases caregiver burden and nursing home placement (Aarsland et al 2005). Several clinical risk factors of cognitive decline in PD have been identified including older age of onset, greater motor symptom burden, having an akinetic-rigid subtype and olfactory dysfunction (Bohnen et al 2010; Baba et al 2012). These predictors were not consistent across the studies (Mollenhauer et al 2006; Compta et al 2009; Alves et al 2010). Liu and colleagues presented a clinicalgenetic score to predict global cognitive impairment within 10 years of PD onset based on clinical variables and the β-glucocerebrosidase (GBA) genotype (Liu et al 2017)
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