Exploration of potential objective and subjective daily indicators of sleep health in normal sleepers

Figures & data

Table 1 Demographic characteristics

		n	%	Low sleep health group	High sleep health group
	Age, M (SD)	27.16 (10.33)		26.60 (10.71)	27.71 (10.34)
Gender	Males	41	49.41	18	21
	Females	42	50.59	20	21
Ethnicity	White British	64	77.06	30	33
	White Irish	1	1.20	1	0
	White Scottish	7	8.43	2	5
	Other White	2	2.41	0	2
	Asian	4	4.82	3	1
	Chinese	2	2.41	1	1
	Undisclosed	3	3.61	1	0
Marital status	Single	64	77.06	33	30
	Married	9	10.84	2	5
	Live-in partner	5	6.02	1	4
	Divorced	2	2.41	1	1
	Separated	1	1.20	0	1
	Undisclosed	2	2.41	1	1
Employment	Full time	31	37.32	12	19
status	Part time	2	2.41	0	1
	Unemployed	1	1.20	0	1
	Retired	1	1.20	0	1
	Student	44	52.98	24	19
	Others	2	2.41	1	1
	Undisclosed	2	2.41	1	0
Education	Pre-bachelor	15	18.06	4	11
	Bachelor	38	45.75	19	19
	Master’s	10	12.04	6	4
	PhD	1	1.20	0	1
	Diploma	3	3.61	2	1
	College	2	2.41	0	1
	MD	2	2.41	0	1
	Others	9	10.84	6	3
	Undisclosed	3	3.61	1	0
Total	N=	83		38	42

Table 2 Multiple regression analyses demonstrating the prediction of sleep health scores by age, sex, subjective SL (diary), and objective SL (actigraphy)

Predictors		B	SE B	b	T	P	R^2 (ΔR^2)
Step 1	Age	0.034	0.036	0.109	0.945	0.348	0.021
	Sex	0.581	0.758	0.088	0.767	0.446
Step 2	Age	0.036	0.032	0.115	1.123	0.265
	Sex	0.400	0.677	0.061	0.592	0.556
	SL (diary)	–0.141	0.031	–0.461	–4.494	<0.001**	233**(0.212**)
Step 3	Age	0.014	0.033	0.045	0.428	0.670
	Sex	0.053	0.678	0.008	0.079	0.937
	SL (diary)	–0.121	0.032	–0.394	–3.765	<0.001**
	SL (actigraphy)	–0.026	0.012	–0.250	–2.221	0.030*	0.282**(0.049*)

Notes:

** P<0.001,

* P<0.05.

Abbreviations: SL, sleep latency; B, unstandardized beta; SE B, standard error of unstandardized beta; b, standardized beta; R², R-squared; DR², R-squared change.

Table S1 Sleep health dimensions, questions, and scoring

Sleep health index dimension	Sleep health components	Question	Scoring	Corresponding item from SHI/SATED
Sleep quality (SHI component)	1. Sleep quality	How would you rate your sleep quality overall?	Very good=3 Fairly good=2 Fairly bad=1 Very bad=0	How many days have you woke up feeling well-rested? (SHI)
	2. Sleep satisfaction	How satisfied are you with your current sleep pattern?	Very satisfied=4 Satisfied=3 Moderately satisfied=2 Dissatisfied =1 Very dissatisfied=0	Are you satisfied with your sleep? (SATED)
	3. Negative impact	I cannot perform my daily tasks as well when I have had a bad night’s sleep…?	Always=6 Almost all of the time=5 Quite a lot=4 Sometimes=3 Very infrequently=2 Hardly ever=1 Never=0	How many days did poor or insufficient sleep significantly impact your daily activities, like your work performance, socializing, exercising, or other typical activities? (SHI)
	4. Sleep efficiency	i) How many hours of actual sleep did you get at night? ii) When have you usually gone to bed at night? iii) When have you usually gotten up in the morning? (number of hours slept/number of hours spent in bed × 100) (scored using NSF guidelines by age group)	1) 18–25 years old >85%=2 65–84%=1 <65%=0 2) 26–64 years old >85%=2 75–84%=1 <75%=0	Do you spend less than 30 minutes awake at night? (including the time it takes to fall asleep and awakenings from sleep) (SATED)
	5. Unintentional dozing	How often have you had trouble staying awake while driving, eating meals, or engaging in social activities?	No problem at all=3 Only a very slight problem=2 Somewhat of a problem=1 A very big problem=0	How many days did you fall asleep without intending to, such as dozing off in front of the TV or in any other situation? (SHI)
Sleep duration (SHI component)	6. Sleep duration	How many hours of actual sleep did you get at night? (scored using NSF guidelines by age group)	1) 18–25 years old 7–9 hours=2 6 or 10–11 hours=1 <6 or >11 hours=0 2) 26–64 years old 7–9 hours=2 6 or 10 hours=1 <6 or >10 hours=0	Do you sleep between 6 and 8 hours per day? (SATED)
	7. Sleep deficit	i) Approximately what time would you get up if you were entirely free to plan your day? ii) Approximately what time would you go to bed if you were entirely free to plan your evening? (ideal duration and difference with actual sleep duration calculated)	<1 hour=3 1–2 hours=2 2–3 hours=1 3–4 hours=0	How many hours of sleep do you need to be well-rested and feel your best? (SHI)
	8. Sleep variability	If you had no commitments the next day, what time would you go to bed compared to your usual bedtime?	Seldom/never later=3 <1 hour later=2 1–2 hours later=1 2+ hours later=0	What about on non-work days or weekends – what time did you most often go to bed on those days? (SHI)
Adaptability (additional component)	9. Sleep adaptability (daytime reactivity)	How likely is it for you to have difficulty sleeping after a stressful experience during the day?	Not likely=3 Somewhat likely=2 Moderately likely=1 Very likely=0	Sleep adaptability questions were included in light of recommendations by Buysse
	10. Sleep adaptability (evening reactivity)	How likely is it for you to have difficulty sleeping after a stressful experience in the evening?	Not likely=3 Somewhat likely=2 Moderately likely=1 Very likely=0

Abbreviations: NSF, National Sleep Foundation; SATED, satisfaction, alertness, timing, efficiency, and duration; SHI, Sleep Health Index.

Table S2 Analyses for the measures of subjective sleep (diary) and objective sleep (PSG and actigraphy): 1) Pearson’s correlations with continuous sleep health scores and 2) between-group (high vs low SH) differences

	Correlations			Between groups					95% LCL	95% UCL	D
	R	P	M (±SD)	Low SHscorersM (±SD)n=38	High SHscorersM (±SD)n=42	T	df	P
SL (minutes)	–0.467	<0.001**	16.66 (10.61)	19.79 (12.61)	13.44 (7.52)	2.744	77	0.008*	1.74	10.97	0.63
WASO (minutes)	–0.203	0.068	9.55 (10.70)	10.97 (11.05)	8.77 (10.59)	0.902	77	0.370	–2.65	7.05	0.21
TIB (minutes)	0.087	0.435	522.25 (59.83)	517.99 (66.29)	522.96 (54.92)	–0.364	77	0.717	–32.17	22.22	0.08
TST (minutes)	0.105	0.353	463.21 (48.39)	459.84 (55.33)	464.47 (41.86)	–0.419	76	0.677	–26.69	17.42	0.09
NWAK	0.051	0.650	0.94 (0.75)	0.92 (0.77)	1.02 (0.73)	–0.583	77	0.562	–4.35	0.24	0.13
% SE	0.185	0.098	87.09 (8.73)	85.61 (9.10)	88.86 (8.39)	–1.637	76	0.106	–7.19	0.70	0.38
PSG sleep continuity parameters
SL (minutes)	0.063	0.569	19.50 (17.18)	20.12 (20.39)	18.24 (14.09)	0.483	78	0.631	–5.86	9.61	0.11
NWAK	0.166	0.147	9.72 (7.86)	8.11 (6.23)	10.83 (8.40)	1.577	73	0.336	–6.14	0.72	0.37
WASO (minutes)	0.056	0.614	22.63 (35.40)	27.29 (46.09)	18.60 (23.34)	1.079	78	0.284	–7.35	24.72	0.24
TST (minutes)	–0.155	0.161	413.30 (58.79)	419.80 (61.98)	409.59 (55.11)	1.257	78	0.212	–15.85	36.27	0.29
% SE	–0.017	0.877	90.51 (17.95)	89.73 (13.00)	92.14 (21.25)	–0.606	78	0.546	–10.36	5.52	0.14
PSG sleep architecture parameters
Percentage wake	0.187	0.102	20.84 (34.71)	12.47 (24.37)	26.79 (38.96)	–1.889	73	0.063	–14.32	7.58	0.44
Percentage Stage 1	0.041	0.712	26.62 (24.91)	24.13 (27.69)	29.32 (21.01)	–0.948	78	0.346	–16.06	5.70	0.21
Percentage Stage 2	–0.049	0.659	39.26 (19.18)	41.65 (18.67)	36.62 (19.51)	1.177	78	0.243	–3.48	13.56	0.27
Percentage slow wave sleep	–0.188	0.089	14.84 (6.91)	15.75 (6.50)	14.30 (7.41)	0.924	78	0.359	–1.67	4.56	0.21
Percentage REM	0.108	0.331	25.32 (14.57)	23.74 (13.77)	26.95 (15.66)	–0.969	78	0.336	–9.80	3.39	0.22
Actigraphy sleep parameters
SL (minutes)	–0.375	<0.001**	39.18 (32.37)	49.59 (35.33)	29.61 (26.55)	2.805	74	0.006*	5.79	34.18	0.65
NWAK	–0.003	0.981	27.72 (8.77)	28.49 (10.43)	26.83 (6.93)	0.704	74	0.484	–4.69	3.14	0.16
WASO (minutes)	–0.100	0.383	55.49 (39.54)	61.20 (40.49)	51.66 (38.70)	1.050	74	0.297	–8.56	27.65	0.24
TST (minutes)	0.040	0.729	402.99 (60.04)	393.16 (67.51)	409.92 (52.93)	–1.211	74	0.230	–44.35	10.83	0.28
% SE	0.168	0.141	80.41 (.8.29)	78.38 (8.83)	82.00 (7.60)	–1.920	74	0.059	–7.37	0.14	0.45
FI	–0.081	0.548	35.51 (14.94)	37.38 (16.91)	33.93 (12.69)	–0.858	54	0.675	–4.61	11.50	0.20

Notes:

** P<0.001,

* P<0.05.

Abbreviations: FI, Fragmentation Index; LCL, lower confidence limit; NWAK, number of awakenings; PSG, polysomnography; SE, sleep efficiency; SH, sleep health; SL, sleep latency; TIB, time in bed; TST, total sleep time; UCL, upper confidence limit; WASO, wake after sleep onset.