Table 1.

Characteristics of the study population

	N	Total sample N = 5,443	N	Accelerometer sample N = 852
Child characteristics
Sex (% girls)	5,443	50.1	852	52.3
Gestational age at birth (weeks)	5,418	39.84 (1.80)	852	39.65 (2.24)
Ethnicity
Dutch%	3,518	64.6	715	84.0
Other‐Western%	509	9.4	49	5.8
Non‐Western%	1,416	26.0	88	10.3
Sleep duration (hours:minutes)		–	852	7.45 (0.42)
Sleep efficiency (%)		–	852	84 (5.1)
Sleep onset (time to fall asleep)		–	852	22.04 (0.55)
Sleep problem score (maternal report)
At 3 years	4,695	1.91 (2.12)	778	1.68 (1.91)
At 6 years	4,805	1.33 (1.81)	808	1.12 (1.62)
At 10 years	3,960	0.83 (1.22)	793	0.83 (1.23)
Sleep problem score at 10 years (child report)	3,598	10.88 (2.47)	772	11.00 (2.47)
Family irregularity	5,443	1.40 (0.39)	852	1.32 (.34)
Maternal characteristics
Age at inclusion (years)	5,442	31.40 (4.66)	852	32.33 (3.85)
Educational level
No education/primary school%	358	6.6	15	1.8
High school/lower vocational training%	2,054	37.7	277	32.5
Higher vocational or academic training%	3,031	55.7	560	65.7
Psychopathology score	5,443	0.24 (0.31)	852	0.19 (0.24)

Data represent means (SDs) unless specified otherwise.