Cognitive complaints in Parkinson's disease patients: from subjective cognitive complaints to dementia and affective disorders

Subjective cognitive complaints (SCC) are frequent in elderly populations. PD patients report SCC more often than healthy controls. The association between SCC, objective cognitive impairment and affective symptoms remains controversial. We assessed consecutive PD patients between March 2014 and March 2015. Presence of SCC was defined as a score >= 1 in the Non-Motor Symptom Assessment Scale for Parkinson's Disease (NMSS) Domain 5. MoCA was used for cognitive impairment assessment. Pill Questionnaire measured the impact in daily activities. PD with Dementia (PDD) and PD with Mild Cognitive Impairment (PDMCI) were defined as the presence of cognitive impairment with or without impact on daily activities. Anxiety and depression were assessed using the Hospital Anxiety and Depression Scales. Significance was set at p < 0.05. From 134 patients, 128 were included. PDD was diagnosed in 21 (16.4%), PDMCI in 31 (24.2%), and 76 (59.4%) had normal cognition (PDCN). SCC were present in 85% of whole cohort and evenly distributed (p = 0.361), PDD (95.2%), PDMCI (83.9%) and PDCN (82.9%). Severity was significantly different between PDD (20.00 +/- 10.81), PDMCI (6.54 +/- 5.5) and PDCN (6.97 +/- 6.98), p < 0.001. A score >= 19 had a specificity of 77.3% and a sensitivity of 78.8% for identifying PDD. In PDCN, SCC severity was found to be related to depression (OR 1.23, CI 95% 1.02-1.47, p = 0.026) more than with MoCA scores (OR: 0.86, CI 95% 0.69-1.05, p = 0.141). SCC are common in PD. Their severity can help distinguish PDD from non-demented PD patients. In PDCN, SCC should alert the clinician for an affective disorder.