Emfit Bed Sensor Activity Shows Strong Agreement with Wrist Actigraphy for the Assessment of Sleep in the Home Setting

Figures & data

Table 1 Cohort Characteristics

Characteristics	Cohort (n=30)
Age (yrs), median (IQR)	25(16–43)
Age <18 years, n (%)	10 (33)
Female sex, n (%)	17 (56.6)
Height (in), median (IQR)	65.5 (62–70)
Weight (lbs), median (IQR)	146.5 (125–168)
Race, n (%)
Asian	4 (13.3)
White	25 (83.3)
Multiracial	1 (3.3)
Sleep habits, n (%)
Sleeps alone	17 (56.6)
Co-sleeps	13 (43.3)
Sleeping problems^a, n (%)
Insomnia	2 (6.6)
Sleep apnea	1 (3.3)
Night terrors	1 (3.3)
Nights recorded per patient, mean (range)	11 (6–14)

Notes: ^aNo subjects reported sleepwalking, sleep paralysis, restless leg syndrome, or narcolepsy.

Abbreviation: IQR, inter quartile range.

Figure 1 Enrollment flow chart. *Consent obtained from a parent or legal guardian for all minors (5–17 years).

Table 2 Correlation of Sleep Parameters Recorded by Emfit Bed Sensor and Actigraphy

	Measurement Type (h:min), Mean (SD)		Difference (min), Mean (95% CI)^a	Bland–Altman 95% Limits of Agreement (h:min)	Bland–Altman Minimal Detecteble Change (min)^b	Inter-Caclass Correlation Coefficient (95% CI)
	Emfit	Actigraphy
Bed entry time	22:31 (1:30)	22:32 (1:29)	−1 (−2 to −1)	−12 to 10	11	0.99 (0.99 to 0.99)
Sleep start	23:21 (1:35)	23:20 (1:35)	1 (0 to 2)	−13 to 15	14	0.99 (0.99 to 0.99)
Sleep end	7:23 (1:35)	7:23 (1:35)	0 (−1 to 1)	−14 to 14	14	0.99 (0.99 to 0.99)
Bed exit time	8:10 (1:46)	8:08 (1:46)	1 (1 to 2)	−9 to 11	10	0.99 (0.99 to 0.99)
Rest interval duration	8:01 (1:27)	8:03 (1:27)	−1 (−2 to 0)	−21 to 19	20	0.99 (0.98 to 0.99)
WASO^c	56.5 (60.4)	53.1 (26.8)	3 (−2 to 9)	−107 to 113	110	0.46 (0.33 to 0.56)

Notes: ^aEmfit minus actigraphy. ^bMinimum Detectable Change = (upper limit of agreement – lower limit of agreement)/2.

Abbreviation: ^cWASO, Wake after sleep onset (min).

Figure 2 Synchronized movement data from actigraphy and bed sensor. Activity data for three different subjects, obtained with actigraphy (AC) and the bed sensor (BS). Light blue indicates the period between bed entry time and bed exit time. Dark blue indicates the period between sleep start and sleep end. Note how activity spikes (black) correlate between the two devices for all three subjects. Subjects 2 and 3 spend time between waking up (increase in activity noted by the two devices) and bed exit (noted by continuous activity on actigraphy and end of activity detected by the bed sensor).

Table 3 Statistical Measures of Epoch-by-Epoch Comparisons Between Actigraphy and Emfit^a

		Actigraphy		Total
		Sleep	Wake
Emfit	Sleep	149,657	10,681	160,338
	Wake	10,335	17,903	28,238
	Total	159,992	28,548	188,576
Sensitivity = 0.62		Specificity = 0.93	Accuracy = 0.88	Kappa = 0.55^b

Notes: ^aTable entries are 1-minute epochs. ^bp-value < 0.0001.