The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C

Figures & data

Table 1 Fabric characteristics of sleepwear

	Mass per area (g·m^−2)	Thickness (mm)	Thermal resistance (m^2·°C·W^−1)	Vapor resistance (m^2·Pa·W^−1)	Air permeability (mm·s^−1)
Sleepwear
Cotton	153.80±0.45	0.51±0.00	0.021±0.0001	3.532±0.07	181.70±7.32
Wool	161.40±0.89	0.41±0.00	0.023±0.0032	2.820±0.06	347.74±7.32
P-value	1.0	0.095	0.033	0.72	1.0
Bedding
Polyester	933	17.3±7.6	0.38	20.51	–
Wool	694	15.7±1.0	0.54	60.09	–
P-value		<0.001

Notes: Data are expressed as Mean±SD where applicable. Sleepwear was tested by the School of Fashion and Textile, RMIT University, Australia, whereas bedding was tested by Australian Wool Testing Authority, Australia. Statistics could not be run on mass per area, thermal resistance, and vapor resistance of bedding due to small sample size (n=2).

Figure 1 Temperature changes during sleep for one participant from bedtime to wake time.

Note: Arrows indicate the peak temperature followed by the temperature plateau that exhibited fluctuations.
Abbreviations: Distal, distal skin temperature; Proximal, proximal skin temperature; Core, core body temperature; DPG, distal–proximal temperature gradient; DCG, distal–core temperature gradient.

Table 2 Mean ± SD for sleep variables of SOL, TST, and SE sleeping in wool or cotton sleepwear averaged across ambient temperature and bedding type

	SOL (min)	TST (min)	SE (%)
Wool sleepwear	11.0±8.2	427.1±50.4	93.2±3.6
Cotton sleepwear	15.0±18.0	420.5±58.5	91.8±7.4
P-value	0.043	0.068	0.082

Note: P-value is between sleepwear conditions, n=134.

Abbreviations: SD, standard deviation; SOL, sleep onset latency; TST, total sleep time; SE, sleep efficiency; min, minute.

Table 3 Effect of ambient temperature conditions on proportion of each sleep stage (mean ± SD) averaged across sleepwear and bedding type

	Stage N1 (%)	Stage N2 (%)	Stage N3 (%)	REM sleep (%)
17ºC	4.8±2.5	51.5±6.3	19.8±5.7	23.9±4.9
22ºC	4.0±2.3	55.0±5.7	18.9±5.1	22.1±4.7
P-value	0.004	<0.001	0.074	0.009

Notes: P-value is between temperature conditions; sleep stages are expressed as a % of total sleep time, n=134.

Abbreviations: SD, standard deviation; REM, rapid eye movement.

Figure 2 Effect of sleepwear and ambient temperature on SOL (A), %N2 (B), and %N3 (C).

Notes: Sleep stages are expressed as a % of total sleep time. Error bars with standard error are displayed. Comparison between sleepwear conditions indicated with ‘a’; Comparison between temperature conditions indicates with a ‘b’; *P<0.05; **P<0.01; ***P<0.001.
Abbreviations: SOL, sleep onset latency; min, minute; N2, sleep stage 2; N3, sleep stage 3.

Figure 3 Temperature predictors of sleep onset latency. The predictors are M-proxT_sk (A), M-disT_sk (B), DCG (C), R-T_c (D).

Notes: Error bars with standard error are displayed. Comparison between sleepwear conditions is indicated by ‘a’; Comparison between temperature conditions is indicated by ‘b’. *P<0.05; **P<0.01; ***P<0.001.
Abbreviations: M-proxT_sk, the magnitude of change in proximal skin temperature; M-disT_sk, the magnitude of change in distal skin temperature; DCG, distal–core body temperature gradient; R-T_c, the rate of change in core body temperature; min, minute.

Table 4 Body temperature predictors of SOL and sleep stages (%N2 and %N3)

Model		R	R^2	Unstandardized		Standardized	Significance
				β	Standard error	β
SOL		0.823	0.678
	(Constant)			5.074	2.720		0.065
	M-proxTsk from bedtime to sleep onset			11.141	1.512	0.484	0.000
	DCG at sleep onset			1.989	0.491	0.214	0.000
	M-disTsk from bedtime to sleep onset			2.759	0.873	0.225	0.002
	M-Tc from bedtime to sleep onset			23.170	6.738	0.263	0.001
	R-Tc from bedtime to sleep onset			219.523	87.055	0.172	0.013
%N2		0.422	0.178
	(Constant)			−28.434	25.932		0.275
	M-proxTsk from sleep onset to the peak			−4.433	0.975	−0.369	0.000
	Proximal Tsk at the peak			2.453	0.741	0.268	0.001
%N3		0.560	0.313
	(Constant)			10.986	1.229		0.000
	R-proxTsk from sleep onset to the peak			98.182	24.968	0.327	0.000
	M-proxTsk from sleep onset to the peak			2.838	0.856	0.271	0.001
	DCG at the peak			−1.647	0.682	−0.182	0.017

Abbreviations: SOL, sleep onset latency; N2, sleep stage 2; N3, sleep stage 3; M, magnitude of temperature change; prox, proximal; T_sk, skin temperature; DCG, distal skin–core body temperature gradient; dis, distal; T_c, core body temperature; R, rate of temperature change.

Table S1 Average sleep parameters for each condition (mean ± SD)

	SOL (min)	WASO (min)	TST (min)	SE (%)	REM sleep latency (min)
WAWB17	9.25±4.95	17.28±12.87	431.94±49.96	94.41±2.81	107.53±34.78
WAPB17	10.53±7.89	18.24±12.79	430.32±51.25	93.86±2.74	95.09±37.18
CAWB17	18.00±21.41	21.06±16.03	420.00±55.57	91.67±6.81	89.21±28.59
CAPB17	18.15±20.94	22.06±21.99	418.71±57.84	91.40±6.96	82.47±24.94
WAWB22	14.89±11.31	20.77±17.32	423.38±54.40	92.29±3.97	96.03±31.50
WAPB22	9.12±6.29	27.44±23.27	422.88±49.68	92.24±4.49	97.88±29.10
CAWB22	10.38±9.09	27.72±48.30	419.44±67.41	91.84±10.53	99.25±42.15
CAPB22	13.27±17.82	22.56±19.07	423.62±58.18	92.23±5.16	112.35±40.21

Abbreviations: SD, standard deviation; min, minute; SOL, sleep onset latency; WASO, wake after sleep onset; TST, total sleep time; SE, sleep efficiency; REM, rapid eye movement; WA, wool apparel; WB, wool bedding; 17, 17°C; PB, polyester bedding; CA, cotton apparel; 22, 22°C.

Table S2 Proximal and distal skin temperature and core body temperature at bedtime, sleep onset, its peak, and nadir

	Bedtime	Sleep onset	Peak	Nadir
17°C
Wool
Proximal	32.92±0.14	33.76±0.18	35.04±0.15	–
Distal	30.30±0.37	32.17±0.35	35.24±0.14	–
Core	36.95±0.07	36.85±0.06	–	36.25±0.07
Cotton
Proximal	33.05±0.14	34.17±0.17	35.06±0.15	–
Distal	30.37±0.37	32.72±0.35	35.45±0.13	–
Core	36.91±0.07	36.82±0.06	–	36.33±0.07
22°C
Wool
Proximal	33.40±0.14	34.26±0.18	35.21±0.15	–
Distal	31.16±0.37	33.08±0.35	35.52±0.13	–
Core	36.91±0.07	36.79±0.06	–	36.34±0.69
Cotton
Proximal	33.40±0.14	34.19±0.18	35.23±0.15	–
Distal	30.95±0.37	32.75±0.35	35.43±0.14	–
Core	36.93±0.07	36.84±0.06	–	36.35±0.07