TABLE 1

Frequency of TWDa by Age, Sex, and Race/Ethnicity Among US High School Students Aged ≥16 y, National YRBS, 2011

CharacteristicAny TWD (≥1 d)1–2 d3–9 d10–19 d20–29 dAll 30 dP Valueb
% (95% CI)% (95% CI)% (95% CI)% (95% CI)% (95% CI)% (95% CI)
Overall
n = 850544.5 (40.8–48.2)10.9 (10.0–11.7)11.8 (10.1–13.6)6.0 (5.2–7.0)4.3 (3.7–5.0)11.5 (10.1–13.1)
Age, y
 1632.6 (28.8–36.6)10.2 (8.9–11.7)8.8 (7.3–10.6)3.8 (2.9–5.0)2.4 (1.8–3.2)7.4 (5.9–9.3)<.001
 1750.0 (44.9–55.1)11.7 (10.4–13.1)13.6 11.2–16.3)7.3 (6.0–8.9)5.1 (4.1–6.4)12.3 (10.5–14.5)
 ≥1857.7 (53.6–61.7)10.6 (8.9–12.5)14.3 (12.5–16.4)8.1 (6.3–10.4)6.6 (5.2–8.3)18.1 (15.4–21.2)
Sex
 Female42.3 (38.0–46.8)11.5 (10.5–12.6)11.1 (9.1–13.5)5.4 (4.6–6.5)4.0 (3.2–5.0)10.3 (8.5–12.3)<.001
 Male46.4 (42.8–50.0)10.2 (9.2–11.4)12.4 (10.6–14.5)6.5 (5.5–7.8)4.6 (3.8–5.4)12.6 (11.2–14.2)
Race/ethnicity
 Whitec50.7 (45.8–55.6)11.4 (10.1–12.9)13.4 11.1–16.1)7.5 (6.3–8.8)5.4 (4.6–6.4)13.0 (11.2–15.0)<.001
 Blackc30.1 (25.1–35.6)9.2 (7.0–12.0)7.4 (5.4–10.0)2.6 (1.8–3.7)2.4 (1.4–4.1)8.6 (6.9–10.6)
 Hispanic38.8 (35.8–41.9)11.5 (10.0–13.1)10.6 (9.2–12.2)4.1 (3.3–5.1)2.7 (2.1–3.4)9.9 (8.3–11.8)
  • CI, confidence interval.

  • a During the 30 d before the survey.

  • b χ2 test, frequency of TWD by demographic distribution.

  • c Non-Hispanic.