Comparison of Actigraphy and Polysomnography in a Sleep Centre Cohort

Polysomnography (PSG) is the gold standard for sleep assessment, but actigraphy offers a low-cost, non-invasive multi-night alternative. MotionWatch 8 was compared to PSG in a tertiary sleep centre cohort (n = 107; age 37.6 ± 14.9 years; 56% female), examining whether actigraphy-PSG agreement varied by demographics, or clinical factors. Patients underwent inpatient PSG with actigraphy for eight nights, including the inpatient night. Actigraphy overestimated total sleep time (TST; +27.31 min), sleep efficiency (SE; +6.09%), and fragmentation index (FI; +11.04 e/h, compared with PSG arousal index, exploratory) and underestimated wake after sleep onset (WASO; -14.86 min) versus PSG (p < 0.05 except WASO). 95% limits of agreement were wide (TST = -96.78 to +151.40 min). Correlations were strong for TST (r = 0.728), moderate for SE (r = 0.540) and WASO (r = 0.581), and weak for FI (r = 0.328; all p < 0.001). Older age was associated with greater TST/SE overestimation and WASO underestimation (p < 0.05). Periodic limb movements in sleep (PLMS; 17%) were linked to smaller TST/SE overestimation, and WASO underestimation, but greater FI overestimation (p < 0.05); psychiatric comorbidity, OSA status, and AHI were non-significant. MotionWacth 8 actigraphy provided clinically meaningful group-level estimates, particularly for TST, but wide interindividual variability, showed actigraphy and PSG not being equivalent or interchangeable. PLMS altered the magnitude and direction of actigraphy-PSG differences, reducing sleep overestimation while exaggerating movement-derived fragmentation. Recording setting influenced actigraphy-derived sleep continuity, so findings from a single inpatient comparison should not generalise to home sleep. These findings support cautious use of actigraphy as a PSG adjunct, with awareness of limitations in detecting quiet wakefulness and movement-related fragmentation.