Table 2.

Means (standard deviations) and percentage distributions of study variables, Add Health.^a

Body mass variables		Number of waves respondents failed to meet a given standard for adequate sleep:
Wave 4 BMI, %
Normal weight	33.6	Below NSF standard, %
Overweight	29.7	0 waves	27.6
Obese	36.8	1 wave	33.1
Wave 1 BMI, %b		2 waves	25.6
Normal weight	72.6	3 waves	10.8
Overweight	15.4	4 waves	2.9
Obese	12.0	Below 7-hour standard, %
Waist circumference 75 percentile, %	26.2	0 waves	45.3
Respondent confounders at Wave 4		1 wave	31.9
Height, cm, mean	170.7 (10.2)	2 waves	16.0
		3 waves	5.5
Male, %	50.7	4 waves	1.4
Age, mean	28.8 (1.8)	Below −0.25 SD standard, %
		0 waves	23.0
Race/Ethnicity, %		1 wave	30.4
Non-Hispanic White	67.3	2 waves	26.8
Non-Hispanic Black	15.8	3 waves	14.8
Hispanic	12.0	4 waves	4.9
Asian	3.2	Below −0.50 SD standard, %
Native American	0.7	0 waves	37.5
Other	1.0	1 wave	32.6
Foreign born, %	5.3	2 waves	19.9
Pregnancy status at wave 4, %		3 waves	7.9
Never pregnant or male	67.0	4 waves	2.0
Ever pregnant	30.0	Below −0.75 SD standard, %
Currently pregnant	3.0	0 waves	49.3
Parent confounders at Wave 1		1 wave	30.4
Mother’s education, yrs, mean	13.2 (2.5)	2 waves	14.6
		3 waves	4.8
Father’s education, yrs, mean	13.3 (2.6)	4 waves	1.0
		Below −1.00 SD standard, %
Family income, $, mean	50,951 (74,391)	0 waves	62.1
		1 wave	26.2
Parents marital status, %		2 waves	9.1
Never married	4.9	3 waves	2.3
Married	72.9	4 waves	0.4
Previously married	22.2
Mother ever smoked, %	50.7
Father ever smoked, %	62.5
Mother obese, %	18.5
Father obese, %	10.6
N (unweighted)	14,800

^aStandard deviations are undefined when applying probability weights to survey data. For any given variable X, we approximate the standard deviation as: (mean (X²) - (mean (X))²)^0.5.

^bBMI data from Wave 1 are based on self-reported height and weight, and are categorized based on CDC growth charts for 2000