Changes in subjective and objective cognitive decline in non‐depressed, non‐demented patients with Parkinson's disease: A 1 to 2 years’ follow‐up

Abstract Background Subjective and objective cognitive impairments were prevalent in patients with Parkinson’s disease (PD), but there is no data on longitudinal cognitive change in these patients in Thailand. We aimed to evaluate the cognition, perception of cognitive decline, and the diagnosis of cognitive impairment in Thai patients with PD after 1‐2 follow‐up. Method Non‐demented, non‐depressed PD patients were included from the Movement Disorder Clinic at Siriraj Hospital. Patients with severe motor symptoms that interfered with cognitive tests were excluded. We used the Montreal Cognitive Assessment‐Thai version (MoCA) to assess cognition. Perception of cognitive decline was assessed by using the Cognitive Change Index (CCI) rated by patients (CCI‐S) and their informants (CCI‐I). All parameters were assessed at baseline and re‐evaluated at 1‐2 years. Association of MoCA, CCI‐S, CCI‐I, the discrepancy of CCI (CCI‐D; CCI‐S minus CCI‐I), apathy score, and patients’ clinical characteristics were analyzed. Result Sixty‐two participants were followed for 18.59±4.55 months. The mean age at baseline was 63.38±9.63 years, and the mean duration of PD diagnosis was 5.63±3.49 years. The MoCA score slightly declined from 20.6±5.1 at baseline to 20.1±4.9 (mean changes ‐0.53±3.2, p=0.195). 47.1% of patients with normal cognition at baseline converted to PD‐MCI. Most (77.8%) PD‐MCI patients remained in the MCI stage, 11.1% turned to dementia, and 11.1% reverted to normal. The CCI‐I and apathy scores increased significantly after 1‐2 years (p=0.003 and <0.001, respectively), but not the CCI‐S. After controlling with age, gender, and education, the 14‐item Starkstein Apathy Scale score at follow‐up was significantly associated with the CCI‐I and the MoCA scores (r = 0.37 and ‐0.34, respectively, both p<0.01). Moreover, change in MoCA scores was significantly associated with the score of CCI‐D at follow‐up (r=‐0.29, p=0.03). Participants with orthostatic hypotension had a lower MoCA score at follow‐up (p=0.04). Conclusion Apathy, informant perception of cognitive decline, but not the cognition, were changed significantly in non‐demented PD patients after 1‐2 years follow‐up. Apathy, the discrepancy of perception of cognitive decline between participant and informant, and orthostatic hypotension may be related to the lower cognition at follow‐up. Further studies with a larger sample size and more extensive neuropsychological evaluation are required.