Table 1. Participant Characteristics, Overall and by Sex.
| Characteristic | Participants, No. (%) | ||
|---|---|---|---|
| Overall (N = 804) | Girls (n = 418) | Boys (n = 386) | |
| Enrollment or early childhood visit | |||
| Mother college graduate | 583 (72.5) | 313 (74.9) | 270 (69.9) |
| Child race/ethnicity | |||
| Black or African American | 126 (15.7) | 62 (14.8) | 64 (16.6) |
| Hispanic or Latino | 35 (4.4) | 18 (4.3) | 17 (4.4) |
| Non-Hispanic white | 517 (64.3) | 275 (65.8) | 242 (62.7) |
| Other | 125 (15.6) | 62 (14.8) | 63 (16.3) |
| Adolescent visit | |||
| Household income >$70 000/y | 608 (75.6) | 317 (75.8) | 291 (75.4) |
| Season of early teen visit | |||
| Winter | 164 (20.4) | 82 (19.6) | 82 (21.2) |
| Spring | 217 (27.0) | 109 (26.1) | 108 (28.0) |
| Summer | 268 (33.3) | 141 (33.7) | 127 (32.9) |
| Fall | 155 (19.3) | 86 (20.6) | 69 (17.9) |
| Age, mean (SD), y | 13.2 (0.9) | 13.2 (0.9) | 13.1 (0.9) |
| Child-reported Tanner stage, mean (SD), pointsa | 3.6 (1.1) | 3.8 (1.0) | 3.4 (1.0) |
| Television viewing, mean (SD), h/d | 2.0 (1.4) | 1.9 (1.3) | 2.2 (1.4) |
| Fast food, mean (SD), servings/wk | 0.7 (1.1) | 0.7 (1.1) | 0.7 (1.1) |
| Sugary drinks, mean (SD), servings/d | 0.8 (0.9) | 0.6 (0.8) | 0.9 (1.0) |
| Parent-reported | |||
| Child sleep duration, mean (SD), h/d | 8.8 (0.9) | 8.8 (0.9) | 8.8 (0.9) |
| Child physical activity, mean (SD), h/d | 1.3 (1.0) | 1.1 (0.9) | 1.4 (1.0) |
| Sleep measures, median (IQR) | |||
| Sleep duration | |||
| min/d | 441 (413-468) | 450 (423-475) | 432 (404-457) |
| h/d | 7.3 (6.9-7.8) | 7.5 (7.1-7.9) | 7.2 (6.7-7.6) |
| Social jet lag, hb | 0.9 (0.3-1.5) | 0.8 (0.3-1.5) | 0.9 (0.4-1.6) |
| Reduced Morningness-Eveningness Scale for Childrenc | 15 (14-16) | 15 (14-16) | 15 (14-16) |
| Mean sleep midpoint, time | |||
| On weekdays | 2:56 (2:23-3:50) | 2:57 (2:24-3:32) | 2:56 (2:22-3:37) |
| On weekends | 3:58 (3:19-4:53) | 4:05 (3:24-4:55) | 3:35 (3:16-4:51) |
| Adiposity and cardiometabolic outcomes, mean (SD) | |||
| BMId (n = 804) | 20.9 (4.5) | 21.0 (4.8) | 20.7 (4.2) |
| BMI z score | 0.37 (1.07) | 0.34 (1.08) | 0.41 (1.06) |
| Waist circumference, cm (n = 804) | 73.0 (11.5) | 72.7 (11.3) | 73.2 (11.6) |
| Sum of skinfolds (subscapular and triceps), mm (n = 803) | 28.2 (13.7) | 29.8 (13.4) | 26.5 (13.9) |
| DXA, kg/m2 (n = 603) | |||
| Fat mass index | 6.3 (3.0) | 6.6 (3.0) | 5.9 (3.0) |
| Trunk fat index | 2.4 (1.5) | 2.6 (1.5) | 2.2 (1.4) |
| Cardiometabolic risk score (n = 479)e | −0.01 (0.60) | 0.00 (0.60) | −0.02 (0.59) |
| HDL cholesterol, mg/dL (n = 541) | 55.3 (13.1) | 54.6 (12.6) | 56.0 (13.6) |
| Triglycerides, mg/dL (n = 541) | 70.6 (34.4) | 73.0 (33.4) | 68.3 (35.2) |
| HOMA-IR (n = 483) | 3.2 (2.1) | 3.5 (2.3) | 2.8 (1.8) |
| Systolic blood pressure, mm Hg (n = 799) | 107.3 (8.9) | 105.8 (8.9) | 108.9 (8.7) |
Abbreviations: BMI, body mass index; DXA, dual-energy x-ray absorptiometry; HDL, high-density lipoprotein; HOMA-IR, homeostatic model assessment of insulin resistance; IQR, interquartile range.
SI conversion factors: To convert HDL cholesterol to millimoles per liter, multiply by 0.0259; and triglycerides to millimoles per liter, multiply by 0.0113.
Child-reported Tanner stage (5-point pubic hair scale).
Social jet lag is the difference in the mean sleep midpoint on weekend days minus the mean sleep midpoint on weekdays.
Morningness-Eveningness Scale is derived from 5 questions regarding adolescents’ preferences for when to get into bed and out of bed, what time of day they had the most energy, and how easy it was to get up in the morning. In this table, higher scores indicate greater morning preference; in multivariable models, we inverted the scores so that higher scores indicate stronger evening preferences.
Calculated as weight in kilograms divided by height in meters squared.
Cardiometabolic risk score is calculated as the mean of 5 sex- and cohort-specific z scores for HDL cholesterol (inverted), log HOMA-IR, log triglycerides, systolic blood pressure, and waist circumference. Higher scores indicate greater risk.