Table 3.

Associations of sleep onset, period and duration with adiposity in white children, stratified by age group

	n	Body mass index z-score				n	Waist circumference (cm)				n	Sum of two-skinfolds (mm)
		Weighted daily average		Weekday to weekend difference			Weighted daily average		Weekday to weekend difference			Weighted daily average		Weekday to weekend difference
		β (95% CI)	P value	β (95% CI)	P value		β (95% CI)	P value	β (95% CI)	P value		β (95% CI)	P value	β (95% CI)	P value
18 months
Model 1
Sleep onset	125	−0.2 (−0.4 to 0.0)	0.086	0.0 (−0.2 to 0.2)	0.70	109	−0.5 (−1.2 to 0.2)	0.18	−0.6 (−1.4 to 0.2)	0.17	84	−1.0 (−2.1 to 0.0)	0.061	−0.1 (−1.2 to 1.0)	0.88
Sleep period	125	0.0 (−0.2 to 0.2)	0.83	0.1 (−0.1 to 0.2)	0.44	109	0.2 (−0.6 to 0.9)	0.64	0.1 (−0.5 to 0.7)	0.70	84	0.1 (−1.0 to 1.2)	0.82	−0.1 (−0.9 to 0.8)	0.86
Sleep duration	108	0.0 (−0.2 to 0.2)	0.91	0.1 (−0.1 to 0.3)	0.37	93	0.1 (−0.7 to 1.0)	0.74	0.3 (−0.4 to 1.1)	0.39	76	−0.1 (−1.0 to 0.8)	0.82	0.1 (−0.9 to 1.1)	0.85
Model 2
Sleep onset	125	−0.2 (−0.4 to 0.0)	0.11	0.1 (−0.1 to 0.3)	0.39	109	−0.5 (−1.2 to 0.2)	0.18	−0.5 (−1.3 to 0.3)	0.23	84	−1.0 (−2.1 to 0.0)	0.060	0.1 (−1.0 to 1.2)	0.85
Sleep period	125	0.0 (−0.2 to 0.2)	0.92	0.0 (−0.1 to 0.2)	0.81	109	0.1 (−0.6 to 0.9)	0.71	0.0 (−0.6 to 0.6)	0.99	84	0.1 (−1.0 to 1.1)	0.91	−0.3 (−1.2 to 0.5)	0.45
Sleep duration	108	0.0 (−0.2 to 0.2)	0.99	0.0 (−0.1 to 0.2)	0.62	93	0.2 (−0.6 to 1.1)	0.57	0.2 (−0.6 to 1.1)	0.55	76	−0.1 (−1.0 to 0.8)	0.86	−0.2 (−1.3 to 0.9)	0.74
Model 3
Sleep onset*	125	−0.2 (−0.5 to 0.0)	0.072	0.2 (−0.1 to 0.4)	0.15	109	−0.6 (−1.5 to 0.3)	0.18	−0.7 (−1.7 to 0.3)	0.15	84	−1.5 (−2.8 to −0.2)	0.025	−0.2 (−1.6 to 1.2)	0.72
Sleep onset†	108	−0.3 (−0.5 to −0.0)	0.044	0.0 (−0.2 to 0.3)	0.79	93	−0.6 (−1.6 to 0.3)	0.20	−0.5 (−1.4 to 0.4)	0.28	76	−1.5 (−2.9 to −0.0)	0.046	−0.0 (−1.3 to 1.2)	0.97
Sleep period	125	−0.1 (−0.3 to 0.1)	0.41	0.1 (−0.1 to 0.3)	0.31	109	−0.2 (−1.0 to 0.7)	0.69	−0.3 (−1.0 to 0.4)	0.40	84	−0.8 (−2.1 to 0.5)	0.22	−0.6 (−1.6 to 0.4)	0.25
Sleep duration	108	−0.1 (−0.2 to 0.1)	0.49	0.1 (−0.1 to 0.3)	0.48	93	0.0 (−0.9 to 0.9)	0.99	0.1 (−0.8 to 0.9)	0.88	76	−0.6 (−1.6 to 0.4)	0.23	−0.3 (−1.5 to 0.8)	0.58
36 months
Model 1
Sleep onset	96	0.0 (−0.2 to 0.3)	0.71	−0.1 (−0.3 to 0.1)	0.32	96	0.2 (−0.7 to 1.1)	0.63	−0.1 (−0.9 to 0.8)	0.89	67	−0.3 (−1.6 to 0.9)	0.57	−0.6 (−1.6 to 0.5)	0.29
Sleep period	96	0.0 (−0.3 to 0.3)	0.98	−0.0 (−0.2 to 0.2)	0.91	96	−0.5 (−1.6 to 0.5)	0.31	−0.3 (−1.1 to 0.5)	0.40	67	−0.2 (−1.6 to 1.2)	0.82	−0.1 (−1.1 to 0.9)	0.83
Sleep duration	90	−0.1 (−0.3 to 0.1)	0.36	−0.0 (−0.2 to 0.2)	0.98	90	−0.5 (−1.4 to 0.4)	0.26	−0.1 (−0.9 to 0.7)	0.81	62	−0.1 (−1.6 to 1.3)	0.88	0.3 (−0.8 to 1.5)	0.54
Model 2
Sleep onset	96	0.0 (−0.2 to 0.3)	0.87	−0.1 (−0.4 to 0.1)	0.38	96	0.1 (−0.9 to 1.0)	0.90	−0.0 (−1.0 to 0.9)	0.92	67	−0.3 (−1.6 to 1.0)	0.68	−0.9 (−2.1 to 0.2)	0.12
Sleep period	96	0.1 (−0.2 to 0.4)	0.66	0.0 (−0.2 to 0.2)	0.81	96	−0.4 (−1.5 to 0.8)	0.51	−0.3 (−1.1 to 0.6)	0.54	67	−0.1 (−1.6 to 1.3)	0.86	0.1 (−1.0 to 1.1)	0.89
Sleep duration	90	−0.1 (−0.3 to 0.2)	0.55	0.1 (−0.2 to 0.3)	0.55	90	−0.4 (−1.3 to 0.5)	0.37	0.1 (−0.8 to 1.0)	0.81	62	−0.2 (−1.7 to 1.3)	0.79	0.5 (−0.8 to 1.8)	0.44
Model 3
Sleep onset*	96	0.0 (−0.2 to 0.3)	0.79	−0.1 (−0.4 to 0.1)	0.33	96	0.0 (−1.0 to 1.0)	0.98	−0.2 (−1.3 to 0.9)	0.71	67	−0.3 (−1.6 to 1.0)	0.67	−1.3 (−2.8 to 0.1)	0.074
Sleep onset†	90	0.0 (−0.3 to 0.3)	0.98	−0.0 (−0.3 to 0.2)	0.72	90	0.0 (−1.0 to 1.0)	0.98	0.1 (−0.9 to 1.1)	0.83	62	−0.4 (−1.9 to 1.2)	0.65	−1.4 (−3.1 to 0.2)	0.085
Sleep period	96	0.1 (−0.2 to 0.4)	0.63	−0.0 (−0.3 to 0.2)	0.76	96	−0.4 (−1.6 to 0.8)	0.52	−0.3 (−1.3 to 0.6)	0.48	67	−0.2 (−1.6 to 1.3)	0.83	−0.6 (−2.0 to 0.7)	0.33
Sleep duration	90	−0.1 (−0.3 to 0.2)	0.55	0.1 (−0.2 to 0.3)	0.68	90	−0.4 (−1.4 to 0.5)	0.37	0.1 (−0.8 to 1.1)	0.76	62	−0.3 (−1.8 to 1.3)	0.74	−0.3 (−2.0 to 1.3)	0.67

Results are beta coefficients (95% CIs) and represent the difference in outcomes for every 1 hour later to sleep, 1 hour longer sleep period or duration, 1 hour later to sleep on weekends than weekdays, or 1 hour longer sleep period or duration on weekends than weekdays. Model 1 was adjusted for sex, age, socioeconomic status, maternal pregnancy age, parity, gestational age, birth weight, maternal body mass index, season of measurement and napping frequency (models for weekday to weekend differences were further adjusted for the average weekday value of the exposure variable). Model 2 was further adjusted for unhealthy snacking, fruit and vegetable intake, and TV viewing (models for weekday to weekend sleep differences were adjusted for average weekday TV viewing and weekday to weekend differences in TV viewing). Model 3 further adjusted sleep period and duration variables for sleep onset, and vice versa (models for weekday to weekend differences were mutually adjusted for average weekday and weekday to weekend differences in the sleep period, duration or onset as appropriate). Statistically significant results (p<0.05) are highlighted bold. Sensitivity analyses confirmed that adjustment for physical activity (collected at 36 months only) did not confound model 3 results, but the association between weighted daily average sleep onset with body mass index z-score at 18 months was attenuated when adjusted for time of last meal (body mass index z-score (n=101): −0.2 (−0.5 to 0.2), p=0.28).

*Adjusted for the sleep period.

†Adjusted for sleep duration.