Objective: To assess whether data obtained from the Parkinson’s KinetiGraph (PKG), an objective movement recording system for Parkinson’s disease (PD), could be used to provide an objective score of nocturnal sleep in PD.    

Background: The PKG uses a wrist worn logger to capture acceleration and derive a bradykinesia score (BKS) every two minutes.  The BKS ranges from 0-160 with higher scores associated with lesser mobility.  Previously we showed that BKS>80 were associated with day time sleep.  We therefore wished to examine whether the BKS could be used to quantify night time sleep.

Methods: The PKG was worn for at least 4 days by 155 people aged over 60 years and without PD (controls) and by 72 people with PD (PwP) scores who also completed a Parkinsons Sleep Score 2 (PDSS 2) and by 46 non PD subjects while undergoing a Polysomnogram (PSG: 36 had a sleep disorder and 10 had normal sleep).  Nocturnal sleep was assessed between the hours of 23:00-06:00 in control subjects by inspecting their sleep pattern an using Principal component analyses.  Four categories of BKS were identified: Active (BKS<50), Inactive (BKS 50-80), Light sleep (BKS 80-110), heavy sleep (BKS>110).  As well, a measure of Fragmentation (length of periods without BKS<80) was developed.  Using these measures, a composite sleep score was produced, which along with the individual measures, was compared with the PDSS 2.  Similar measures were produced in people undergoing PSGs. 

Results: The PKG Sleep Score distinguished between definite sleep abnormality, as measured by PSG with a Selectivity of 93% and Sensitivity of 95%.  There was a high probability that subjects with a PDSS 2 would have an abnormal PKG scores (c2<0.001).  The scores in PwP were significantly different from controls and deteriorated with progression of disease.  Factors that best predicted good sleep during the period 23:00-06:00 were a high proportion of BKS>110, a low proportion of BKS<50 and reduced fragmentation. 

Conclusions: The findings suggest that PKG nocturnal sleep score can pick between normal and abnormal sleepers with high accuracy but further work is required to confirm whether it can be used to screen those who need sleep studies and to detect the nature of a sleep disturbance.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/using-an-objective-measure-of-movement-to-quantify-night-time-sleep/