Introduction Clock drawing (CD) requires executive function, attention and visuospatial ability. Our objective was to investigate CD in Parkinson's subjects with and without cognitive impairment.

Methods 107 subjects completed the Montreal Cognitive Assessment (MoCA), classifying into normal cognition (PD-NC – MoCA ≥26) and cognitive impairment (PD-CI–MoCA <26). CD was scored using MoCA criteria; a maximum of 3 points, one each for correct contour, clock face and clock hands.

Results PD-CI (n=57) and PD-NC were matched for all demographics except age (PD-CI were older, P 0.032). 35% of PD-CI scored full marks compared to 90% of PD-NC (sensitivity 0.64, specificity 0.9, age adjusted-odds ratio for predicting PD-CI 15.63, 95% CI 5.18 – 47.62, P<0.001). 88% of PD-CI scored points for contour and 60% scored points for clock face. In contrast, all PD-NC scored points for contour and clock face (P <0.001). 42% of PD-CI and 90% of PD-NC correctly drew clock hands (P<0.001).

Conclusions In this cohort, inability to score maximum points for CD was associated with PD-CI. Correctly drawing clock hands was the hardest component for both groups. Incorrect contour or clock face was highly specific for PD-CI.