Background: Postural instability gait difficulty (PIGD) motor phenotype in Parkinson’s disease (PD) is associated with a faster rate of cognitive decline than in tremor dominant cases and may be a risk factor for incident dementia. People with PD display attentional deficits; however it is not clear whether attentional deficits in non-demented PD patients are associated with (i) PIGD phenotype and/or (ii) subsequent cognitive decline.
Aims: (i) To examine rates of cognitive decline (MMSE and CAMCOG) over three years in non-demented PD subjects aged over 65, (ii) using Cognitive Drug Research computerised assessment test battery determine rate of change in power of attention (PoA) scores over time (sum of mean choice reaction time, simple reaction time and digit vigilance reaction time scores), (iii) determine whether PIGD phenotype is associated with changes in PoA and (iv) establish whether baseline PoA is associated with subsequent cognitive decline.
Results: 14 subjects (38%) were classified as PIGD motor phenotype at baseline. Cognitive decline was greater in PIGD compared to non-PIGD subjects (p<0.02). PIGD phenotype was not associated with baseline PoA score although it was associated with subsequent worsening in PoA (mean PoA increase/year: Non-PIGD subjects, 11.3 ms; PIGD subjects, 244.0 ms; p=0.02). Higher baseline PoA scores were associated with greater cognitive decline (MMSE, p=0.03; CAMCOG, p=0.05) independent of PIGD status.
Conclusion: PIGD phenotype and attention deficits are independently associated with a greater rate of cognitive decline in non-demented PD patients. We propose that subtle attentional deficits in non-demented PD patients predict subsequent cognitive impairment.