Two-year changes in sleep duration are associated with changes in psychological distress in adolescent girls and boys: the fit futures study

Figures & data

Figure 1. Study flowchart, Fit Futures (FF1) 2010–2011 and Fit Futures 2 (FF2) 2012–2013.

Figure 2. Sleep duration in hours at baseline and follow-up, in girls and boys, respectively. Fit Futures 2010–2011 and 2012–2013.

Table 1. Baseline characteristics for girls and boys, stratified on sleep duration. Fit Futures 2010–2011.

	Girls							Boys
	≤6 h		>6 h to >9 h		≥9 h			≤6 h		>6 h to >9 h		≥9 h
	n	Mean (SD)	n	Mean (SD)	n	Mean (SD)	p-value*	n	Mean (SD)	n	Mean (SD)	n	Mean (SD)	p-value*
Age (years)	85	16.11 (0.38)	280	16.16 (0.44)	8	16.13 (0.84)	0.513	75	16.17 (0.55)	199	16.08 (0.48)	17	16.12 (0.78)	0.414
Self-rated health	85	3.58 (0.84)	277	4.05 (0.71)	8	3.50 (0.54)	0.087	74	3.96 (0.86)	199	4.24 (0.86)	17	3.94 (0.90)	0.210
HSCL-10	85	1.86 (0.69)	280	1.51 (0.48)	8	1.71 (0.67)	<0.001	75	1.50 (0.48)	199	1.31 (0.36)	17	1.32 (0.47)	0.014
Body height (cm)	85	1.64 (6.22)	279	165.24 (6.73)	8	165.59 (7.34)	0.463	75	176.49 (6.85)	199	177.69 (6.26)	17	179.36 (6.46)	0.184
Body weight (kg)	85	59.56 (11.21)	279	60.75 (9.99)	8	62.95 (21.08)	0.659	75	70.99 (16.36)	199	69.50 (13.10)	17	74.98 (16.64)	0.271
BMI (kg/m^2)	85	22.13 (4.38)	279	22.24 (3.38)	8	22.82 (6.90)	0.948	75	22.73 (4.68)	199	21.97 (3.71)	17	23.28 (5.02)	0.214
Age menarche (years)	85	12.58 (1.31)	274	12.73 (1.08)	8	12.88 (0.99)	0.501
hs-CRP (mg/ L)	69	1.88 (3.00)	253	1.41 (3.24)	8	1.07 (1.44)	0.512	64	1.72 (4.60)	183	1.25 (2.37)	16	1.33 (1.46)	0.740
IL-6 (NPX)	69	3.08 (9.67)	254	2.79 (0.49)	8	2.80 (0.49)	0.086	68	2.80 (0.50)	191	2.88 (0.67)	17	2.54 (0.55)	0.082
TGF – α (NPX)	69	3.94 (0.54)	254	3.88 (0.60)	8	3.98 (0.70)	0.711	68	3.64 (0.62)	191	3.57 (0.57)	17	3.40 (0.44)	0.281
TRANCE (NPX)	69	5.52 (0.63)	254	5.50 (0.62)	8	5.81 (0.35)	0.351	68	5.99 (0.52)	191	6.02 (0.51)	17	6.05 (0.61)	0.901
TWEAK (NPX)	69	8.89 (0.34)	254	8.89 (0.32)	8	8.80 (0.31)	0.726	68	9.02 (0.31)	191	9.03 (0.27)	17	8.95 (0.25)	0.500
Vitamin D (nmol/L)	69	41.51 (18.66)	254	45.03 (16.91)	8	39.56 (12.47)	0.242	69	33.44 (16.48)	191	34.53 (14.81)	17	38.38 (18.34)	0.499
Smoking	85		280		8		0.001	75		199		17		0.002
No, never	56	65.9%	240	85.7%	8	100.0%		51	68.0%	171	85.9%	14	82.4%
Sometimes	24	28.2%	34	12.1%	0	0.0%		18	24.0%	27	13.6%	3	17.6%
Daily	5	5.9%	6	2,1%	0	0.0%		6	8.0%	1	0.5%	0	0%
Snuffing	85		280		8		0.298	75		198		17		0.010
No, never	52	61.1%	198	70.7%	7	87.5%		38	50.7%	143	72.2%	11	64.7%
Sometimes	14	16.5%	40	14.3%	1	12.5%		11	14.7%	21	10.6%	1	5.9%
Daily	19	22.4%	42	15.0%	0	0%		26	34.7%	34	17.2%	5	29.4%
Alcohol intake	85		280		8		0.024	74		199		17		<0.001
Never	14	16.5%	77	27.5%	4	50.0%		16	21.6%	76	38.2%	9	52.9%
Once per month or less	37	43.5%	132	47.1%	3	37.5%		27	36.5%	84	42.2%	3	17.6%
Twice or more per month	34	40.0%	71	25.4%	1	12.5%		34	45.9%	39	19.6%	5	29.4%
Physical activity	85		280		8		0.015	75		199		17		0.331
Physically inactive	15	17.6%	32	11.4%	0	0.0%		24	32.0%	52	26.1%	4	23.5%
Some light physical activity	42	49.4%	103	36.8%	4	50.0%		16	21.3%	51	25.6%	3	17.6%
Regular physical activity and training	22	25.9%	86	30.1%	2	25.0%		21	28.0%	48	24.1%	2	11.8%
Regular hard physical activity (for competitive sports)	6	7.1%	59	21.1%	2	25.0%		14	18.7%	48	24.1%	8	47.1%
Current infection	85		278		8		0.667	75		198		17		0.330
No	74	87.1%	236	84.9%	8	100.0%		64	85.3%	165	83.3%	12	70.6%
Yes	11	12.9%	42	15.1%	0	0.0%		11	14.7%	33	16.7%	5	29.4%
Chronic disease	85		278		8		0.725	75		197		17
No	61	71.8%	187	67.3%	6	75.0%		59	78.7%	141	71.6%	9	52.9%
Yes	24	28.2%	91	32.7%	2	25.0%		16	21.3%	56	28.4%	8	47.1%
Hormonal contraceptives	85		277		8		0.083
No	44	51.8%	179	64.6%	6	75.0%
Yes	41	48.2%	98	35.4%	2	25.0%
PDS status								63		158		16		0.358
Not begun								0	0.0%	0	0.0%	0	0.0%
Barely started								7	11.1%	16	10.1%	0	0.0%
Underway								48	76.2%	111	70.3%	11	68.8%
Completed								8	12.7%	31	19.6%	5	31.3%
High School Program	85		280		8		0.219	75		199		17		0.006
General Studies	44	51.8%	155	55.4%	4	50.0%		24	32.0%	81	40.7%	2	11.8%
Sports and Physical	4	4.7%	31	11.1%	0	0.0%		6	8.0%	31	15.6%	6	35.3%
Vocational	37	43.5%	94	33.6%	4	50.0%		45	60.0%	87	43.7%	9	52.9%

Bold: Statistically significant with a p-value of 0.05. Mean (SD) of continuous variable and percentages of categorical variables are reported. BMI, Body Mass Index; hs-CRP, high-sensitive C-reactive protein; IL6-α: Interleukin 6 alpha; TGF-α: Transforming growth factor alpha; TRANCE, Tumor Necrosis Factor-related activation-induced cytokine (O14788: TNF-related activation-induced cytokine within limits of detection); TWEAK, Tumor necrosis factor-like weak inducer of apoptosis (O43508: TNF-like weak inducer of apoptosis within limits of detection); NPX, Normalized protein expression; Vitamin D, Standardized version of (25-OH)D; PDS status, Pubertal Development Scale status.

*One-way ANOVA was used to compare continuous data across the sleep duration categories. When Levene’s test indicated unequal variances, Welch’s corrected F- and p-values are reported. Fisher’s exact test was used to compare categorical data across sleep duration.

Table 2. Crude and adjusted associations between sleep duration and psychological distress (Hopkins Symptom Check List HSCL-10), assessed by linear regressions, 1 unit sleep duration equals 30 min.

			95% CI
	n	B	Lower	Upper	p-value	R^2
Girls
Baseline univariate	373	−0.132	−0.183	−0.081	<0.001*	0.066
Follow-up univariate	372	−0.134	−0.186	−0.082	<0.001*	0.065
Model 1	372	−0.090	−0.131	−0.048	<0.001*	0.047
Model 2	361	−0.068	−0.109	−0.027	0.001*	0.137
Boys
Baseline univariate	291	−0.089	−0.127	−0.051	<0.001*	0.069
Follow-up univariate	294	−0.087	−0.132	−0.042	<0.001*	0.048
Model 1	291	−0.054	−0.091	−0.017	0.005*	0.027
Model 2	117	−0.078	−0.125	−0.031	0.001*	0.376

The results are presented for girls and boys, respectively. Fit Futures from baseline 2010–2011 and follow-up in 2012–2013. B: Unstandardized beta. Baseline univariate: Crude analysis baseline. Follow-up univariate: Crude analysis follow-up. Model 1: Crude analysis with change score sleep duration as exposure and change score Hopkins Symptom Checklist (HSCL-10) as outcome. Model 2 for girls: Model 1 + use of contraceptives, change score smoking, change score snuffing, change score physical activity and change score self-rated health. Model 2 for boys: Model 1 + chronic disease, change score current infection, change score self-rated health, change score smoking, high-sensitive C-reactive protein, interleukin 6 alpha and transforming growth factor alpha.

*Statistically significant with a p-value cut-off of 0.05.

Data availability statement

Data may be obtained from a third party, UiT – The Artic University of Norway. Restrictions apply to the availability of these data, which were used under license for the current study, and are thus not publicly available.