Table 4

RR (from covariate-adjusted models)

Low: <1 hourHigh: 3 to <5 hoursVery high: 5+ hours
RR (95% CI)P valueRR (95% CI)P valueRR (95% CI)P value
Late sleep onset
(school days)
0.67 (0.58 to 0.78)<0.0011.17 (1.02 to 1.33)<0.051.68 (1.52 to 1.84)<0.001
Late sleep onset
(free days)
0.66 (0.58 to 0.75)<0.0011.2 (1.06 to 1.35)<0.011.69 (1.57 to 1.81)<0.001
Late wake time
(school days)
1.03 (0.72 to 1.48) ns 1.54 (1.02 to 2.29)<0.051.91 (1.3 to 2.76)<0.01
Late wake time
(free days)
0.83 (0.72 to 0.95)<0.011.09 (0.94 to 1.26) ns 1.41 (1.24 to 1.59)<0.001
Sleep onset latency >30 min0.93 (0.84 to 1.03) ns 1.07 (0.94 to 1.21) ns 1.08 (0.97 to 1.2)ns
Frequent nighttime awakenings1.03 (0.89 to 1.19) ns 1.07 (0.89 to 1.28) ns 1.28 (1.09 to 1.5)<0.01
  • RR transformed from ORs in covariate-controlled binomial logistic regression models (see table 3). Reference category is average (1 to <3 hours). For example, RR of 1.68 means very high users are 68% more likely to fall asleep late on school days than comparable average users.

  • RR, relative risks; ns, not significant.