Table 1.
Study population characteristics, National Longitudinal Study of Adolescence Wave II respondents with DNA
| European American | African American | Hispanic American | Total | |
|---|---|---|---|---|
| N | 4,788 | 1,612 | 1,242 | 7,642 |
| Age in y, mean (SD) | 16.3 (1.8) | 16.1 (1.6) | 16.4 (1.6) | 16.2 (1.6) |
| Male sex, N (%) | 2,275 (47.5) | 731 (45.4) | 614 (49.3) | 3,620 (47.4) |
| Age- and sex-specific BMI Z-score1, mean (SD) | 0.29 (1.10) | 0.51 (1.08) | 0.46 (1.11) | 0.37 (1.10) |
| Screen time hr/wk2, mean (SD) | 19.1 (16.9) | 27.8 (22.3) | 21.1 (17.6) | 21.2 (18.6) |
| 1st quartile, hr/wk | 0–7 | 0–10 | 0–8 | 0–8 |
| 2nd quartile, hr/wk | 8–14 | 11–22 | 9–15 | 9–15 |
| 3rd quartile, hr/wk | 15–25 | 23–40 | 16–29 | 16–29 |
| 4th quartile, hr/wk | 26+ | 41+ | 30+ | 30+ |
| Bouts3 of physical activity/wk, mean (SD) | 6.3 (3.9) | 5.8 (3.5) | 5.8 (3.8) | 6.1 (3.8) |
| Current smoking, N (%) | 1,938(40.5) | 288 (17.8) | 347 (27.9) | 2,573 (33.7) |
| Region, N (%) | ||||
| West | 714 (14.9) | 238 (14.8) | 497 (40.0) | 1,449 (19.0) |
| Midwest | 1,776 (37.1) | 317 (19.7) | 92 (7.4) | 2,185 (28.6) |
| South | 1,572 (32.8) | 966 (59.9) | 477 (38.4) | 3,015 (39.5) |
| Northeast | 726 (15.2) | 91 (5.7) | 176 (14.2) | 993 (13.0) |
1
BMI: Body mass index, calculated as weight in kilograms divided by height in meters squared and scaled for sex and age [Ogden, C.L., et al., Centers for Disease Control and Prevention 2000 growth charts for the United States: improvements to the 1977 National Center for Health Statistics version. Pediatrics, 2002. 109(1): p. 45–60.]
2
Screen time is measured as the total sum of hours of screen time from television, video, and computer games per week.
3
Bouts of physical activity include sessions of exercise or sport where intensity was enough to sweat.