A comparison of agreement between actigraphy and polysomnography for assessing sleep during posttraumatic amnesia

Abstract

Study objectives: Sleep disturbance often emerges in the early recovery phase following a moderate to severe traumatic brain injury, known as posttraumatic amnesia. Actigraphy is commonly employed to assess sleep, as it is assumed that patients in posttraumatic amnesia (who display confusion, restlessness, and agitation) would better tolerate this measure over gold-standard polysomnography (PSG). This study evaluated the agreement between PSG and actigraphy for determining (sleep/wake time, sleep efficiency, sleep latency, and awakenings) in patients experiencing posttraumatic amnesia. It also compared the epoch-by-epoch sensitivity, specificity, and accuracy between the Actigraph device's 4 wake threshold settings (low, medium, high, and automatic) to PSG.

Methods: The sample consisted of 24 inpatients recruited from a traumatic brain injury inpatient rehabilitation unit. Ambulatory PSG was recorded overnight at bedside and a Philips Actiwatch was secured to each patient's wrist for the same period.

Results: There were poor correlations between PSG and actigraphy for all parameters (Lin's concordance correlation coefficient = < 0.80). The low threshold displayed the highest correlation with PSG for wake and sleep time, albeit still low. Actigraphy displayed low specificity (ranging from 17.1% to 36.6%). There appears to be a greater disparity between actigraphy and PSG for patients with increased wake time.

Conclusions: Actigraphy, while convenient, demonstrated poorer performance in determining sleep-wake parameters in patients with significantly disturbed sleep. Ambulatory PSG can provide a clearer understanding of the extent of sleep disturbances in these patients with reduced mobility during early rehabilitation. Study findings can help design future protocols of sleep assessment during posttraumatic amnesia and optimize treatment.

Citation: Fedele B, McKenzie D, Williams G, Giles R, Olver J. A comparison of agreement between actigraphy and polysomnography for assessing sleep during posttraumatic amnesia. J Clin Sleep Med. 2022;18(11):2605-2616.

Keywords: actigraphy; brain injuries; polysomnography; rehabilitation; sleep; traumatic.

Figure 1. Patient example of hypnogram (PSG) and actogram (actigraphy) for sleep period.

Example of a patient’s hypnogram (a graphical representation of sleep period from PSG) and actogram (a graphical representation of sleep period from actigraphy) for the same time period. (A) Actogram: The black lines indicate activity as measured by actigraphy and the dark blue shaded area indicates sleep time. This patient displayed increased movement (black activity lines) throughout their sleep period. (B) Hypnogram: The colored blocks represent each stage of sleep as indicated on the left, and the white gaps indicate wake time. For this patient, the majority of sleep was spent in N1 and N2 with no N3 (deep sleep). N1 = nonrapid eye movement stage 1, N2 = nonrapid eye movement stage 2, N3 = nonrapid eye movement stage 3, PSG = polysomnography, R = rapid eye movement, W = wake time.

Figure 2. Bland-Altman plots of PSG and actigraphy (low threshold) measurement for (A) wake time and (B) sleep time.

Each dot represents a single patient within the analytic sample. The horizontal x-axis displays the mean of the 2 measures (eg, mean of PSG wake time and actigraphy wake time) and the vertical y-axis displays the difference between the 2 measures (eg, PSG wake time minus actigraphy wake time). The solid horizontal line represents the mean of the differences (mean bias) between PSG and actigraphy. Mean differences that are positive values (dots above the mean bias) signify that actigraphy underestimates the parameter and the reverse (overestimates) for negative mean difference values (dots below the mean bias). Perfect agreement between both measures for the given variable would display patients (dots) residing exactly on the mean bias line. The dotted lines reflect the 95% limits of agreement for the mean bias. PSG = polysomnography.