Table 2.

Participant characteristics, overall, and by category of body mass index

	Overall	Normal weight	Overweight	Obese	p value
N	411	276	93	42
Age, years	10.1 (1.25)	10.1 (1.24)	10.1 (1.15)	9.90 (1.51)	0.59
Sex, boys/girls, n	202/209	135/141	43/50	24/18	0.5
Body mass index, z-score	0.86 (1.36)[-3.35,5.46]	0.15 (0.98)[-3.35, 2.71]	1.93 (0.38)[1.25, 2.78]	3.14 (0.64)[2.21, 5.46]	<0.0001
Rest–activity rhythm characteristics
Mesor	46.6 (6.1)[21.7, 61.3]	47.1 (5.98)[21.7, 61.3]	46.2 (6.05)[22.9, 57.4]	44.4 (6.19)[28.6, 56.1]	0.05
Acrophase, clock hour	15.0 (0.69)[13.3, 16.9]	15.0 (0.69)[13.4, 16.9]	15.1 (0.65)[13.3, 16.6]	15.2 (0.73)[13.6, 16.6]	0.05
Relative amplitude	0.84 (0.05)[0.62, 1.00]	0.84 (0.04)[0.68, 1.00]	0.84 (0.04)[0.72, 0.97]	0.83 (0.07)[0.62, 0.93]	0.62
Interdaily stability	0.38 (0.08)[0.21, 1.04]	0.39 (0.07)[0.21, 1.00]	0.38 (0.08)[0.22, 0.98]	0.38 (0.12)[0.22, 1.04]	0.12
Intradaily variability	0.87 (0.06)[0.60, 1.05]	0.86 (0.06)[0.60, 1.03]	0.87 (0.07)[0.65, 1.05]	0.88 (0.06)[0.72, 1.03]	0.24
M10 midpoint, clock hour	15.2 (1.32)[12.0, 19.0]	15.2 (1.32)[12.0, 19.0]	15.2 (1.29)[12.4, 19.0]	15.2 (1.38)[12.3, 18.1]	0.91
L5 midpoint, clock hour	2.5 (1.2)[0.6, 6.0]	3.4 (1.2)[0.6, 6.0]	3.8 (1.05)[1.6, 5.5]	3.5 (1.11)[1.5, 5.6]	0.03
CFI	0.60 (0.04)[0.47, 0.82]	0.60 (0.04)[0.51, 0.81]	0.60 (0.04)[0.51, 0.79]	0.59 (0.05)[0.47, 0.82]	0.29
Other lifestyle factors
Total sleep duration, h	7.68 (0.68)[6.45, 12.6]	7.68 (0.59)[6.45, 9.77]	7.69 (0.77)[6.48, 12.2]	7.65 (0.99)[6.47, 12.6]	0.63
Daytime motor activity, ∆°/min	73.4 (10.0)[38.2, 98.4]	74.5 (9.8)[38.2, 98.4]	72.4 (9.5)[38.6, 90.7]	68.5 (11.2)[43.8, 86.5]	0.001

Data are n or mean (SD) [range]. p values obtained with the Kruskal–Wallis test for continuous variables and χ² test for categorical variables.

M10 midpoint, timing of most active 10-h episode; L5 midpoint, timing of the least active 5 h episode; CFI, circadian function index.