Table 1.

Bivariate Associations of Selected Parent and Child Characteristics With Infant Sleep Duration, With Data From 915 Mother-Infant Pairs From Project Viva

		Sleep Duration From Ages 6 mo to 2 y, Mean, h/d
Characteristic	Overall (N = 915)	< 11 (n = 105)	11 to < 12 (n = 224)	12 to < 13 (n = 314)	≥ 13 (n = 272)	P for Trend
Maternal
Age, mean (SD), y	32.6 (4.8)	32.4 (5.4)	32.6 (5.5)	32.9 (4.3)	32.4 (4.4)	.63
Prepregnancy BMI, mean (SD)	24.4 (4.9)	25.0 (4.6)	24.4 (4.9)	24.6 (5.2)	23.9 (4.5)	.19
Gestational weight gain, mean (SD), kg	15.6 (5.3)	15.0 (5.5)	15.9 (5.7)	15.5 (4.9)	15.7 (5.3)	.55
Household income > $70 000, %	66	56	65	76	74	< .001
College graduate or more, %	76	57	77	82	75	.007
Multipara, %	51	56	48	48	55	.71
Married or cohabiting, %	95	93	92	96	97	.01
Smoked during early pregnancy, %	8	12	10	8	7	.07
Paternal
BMI, mean (SD)	26.4 (3.7)	26.3 (3.7)	26.4 (4.3)	26.2 (3.5)	26.5 (3.5)	.88
Child
Male, %	50	45	55	51	47	.60
Race/ethnicity, %						< .001
White	73	45	66	80	83
Black	10	22	13	6	6
Hispanic	3	9	3	2	2
Other	14	25	18	12	10
Overweight at age 3 y, %	9	13	12	7	7	.05
Birth weight, mean (SD), kg	3.51 (0.56)	3.41 (0.64)	3.49 (0.49)	3.52 (0.58)	3.55 (0.56)	.18
BMI z score at age 3 y, mean (SD)	0.44 (1.03)	0.50 (1.12)	0.52 (1.05)	0.39 (1.02)	0.40 (0.98)	.43
Sum of SS and TR skinfold thicknesses at age 3 y, mean (SD), mm	16.66 (4.06)	16.63 (5.07)	17.00 (4.36)	16.39 (3.87)	16.71 (3.58)	.41
Ratio of SS and TR skinfold thicknesses at age 3 y, mean (SD)	0.64 (0.16)	0.68 (0.16)	0.64 (0.15)	0.63 (0.16)	0.63 (0.16)	.06
Duration of breastfeeding, mean (SD), mo	6.6 (4.5)	6.1 (4.8)	6.7 (4.6)	6.8 (4.5)	6.4 (4.3)	.50
Television viewing at age 2 y, mean (SD), h/d	1.4 (1.1)	1.8 (1.6)	1.5 (1.3)	1.4 (1.0)	1.2 (0.86)	< .001
Active play at age 2 y, mean (SD), h/d	3.1 (1.8)	3.2 (1.8)	3.3 (1.8)	3.0 (1.7)	3.0 (1.8)	.30

Abbreviations: BMI (calculated as the weight in kilograms divided by the height in meters squared); SS, subscapular; TR, triceps.