Objective: This study investigated 1) pro-saccades in a newly diagnosed cohort of Parkinson’s disease (PD) compared to healthy older adult controls at baseline, and 2) whether baseline pro-saccades can predict attentional decline over 18months better than traditional computerised testing in PD and controls.

Background: Cognitive impairments, such as attentional decline and fluctuation, are common in PD and impact saccadic eye-movements [1]. Accuracy, control and speed of saccades have been linked to cognitive processes, primarily attention [1]. Saccadic deficits have also been linked to poor mobility and may impact falls risk [2]. Saccades may therefore be a useful non-invasive biomarker for cognitive decline or dementia in PD.

Methods: Pro-saccades were recorded using a saccadometer (Ober consulting) in 97 PD and 71 healthy controls at baseline. Pro-saccade characteristics included latency, duration, amplitude, average and peak velocity. Attention (power of attention and fluctuating attention (FA)) were assessed using a computerized battery. Independent t-tests compared pro-saccade characteristics in PD and controls. Scatterplots and linear multiple regression (controlled for age, sex, education and change in levodopa) assessed predictive value of baseline pro-saccades in relation to change in FA over 18months.

Results: Pro-saccades were significantly impaired in PD compared to controls at baseline (amplitude; p=.019). Increased FA over 18months was associated with more variable pro-saccade duration (CV) at baseline in PD (r=.30, p=.003) and controls (r=.24, p=.046). Pro-saccade duration (CV) was then entered into a regression model and was an independent predictor of change in FA (CV) in PD (F=2.78, p=.022, r²=.134 (β=-.282, p=.006)), but not controls. Conversely, baseline FA was unable to predict change in FA in PD, whereas the opposite was true for controls (F=5.56, p=.001, r²=.244 (β=-.514, p<.001)).

Conclusions: Pro-saccades are impaired in PD compared to controls at diagnosis.  Baseline pro-saccade duration (CV) rather than baseline FA was a significant predictor of change in FA over 18months in PD, but not in controls. Therefore, saccades are a feasible biomarker of attentional decline in PD.

References:

1. Ballanger, B., J Neurophys, 2009. 102(5): p.2578-80
2. Stuart, S., et al., Neuro&BioRev, 2016. 62: p.76-88

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MDS Abstracts - https://www.mdsabstracts.org/abstract/pro-saccades-predict-decline-in-attention-over-18months-in-newly-diagnosed-parkinsons-disease/