Table 3.
Interrelationships between measures of sleep quality and sleep quantity in Norwich, United Kingdom, from 2006 to 2007.
| Time in bed | Sleep duration | Sleep proportion | Time in bed | Sleep duration | Sleep proportion | ||
|---|---|---|---|---|---|---|---|
| Mean (SD) h | Mean (SD) h | Median (IQR) | Mean (SD) h | Mean (SD) h | Median (IQR) | ||
| Difficulty falling asleep | Difficulty falling asleep | ||||||
| Usually (n = 179) | 8:40 (1.20)⁎⁎⁎ | 5:46 (1.35)⁎⁎⁎ | 0.65 (0.56–0.80)⁎⁎⁎ | Usually (n = 478) | 8:57 (1.05)⁎⁎⁎ | 5:29 (1.16)⁎⁎⁎ | 0.63 (0.53–0.71)⁎⁎⁎ |
| Sometimes (n = 1104) | 8:36 (0.86) | 6:41 (1.00) | 0.79 (0.71–0.87) | Sometimes (n = 2494) | 8:49 (0.82) | 6:40 (1.04) | 0.77 (0.68–0.84) |
| Never (n = 2274) | 8:30 (0.86) | 7:12 (0.90) | 0.87 (0.80–0.92) | Never (n = 1951) | 8:43 (0.82) | 7:14 (0.94) | 0.84 (0.77–0.91) |
| Waking up during the night | Waking up during the night | ||||||
| Usually (n = 298) | 8:39 (1.03)⁎⁎⁎ | 5:46 (1.13)⁎⁎⁎ | 0.68 (0.58–0.76)⁎⁎⁎ | Usually (n = 690) | 8:52 (0.97)⁎⁎⁎ | 5:34 (1.12)⁎⁎⁎ | 0.63 (0.55–0.73)⁎⁎⁎ |
| Sometimes (n = 1933) | 8:36 (0.85) | 6:55 (0.96) | 0.82 (0.74–0.89) | Sometimes (n = 2993) | 8:49 (0.81) | 6:47 (0.99) | 0.78 (0.70–0.85) |
| Never (n = 1326) | 8:26 (0.88) | 7:19 (0.86) | 0.88 (0.82–0.93) | Never (n = 1240) | 8:42 (0.86) | 7:26 (0.86) | 0.87 (0.80–0.93) |
| Early awakening | Early awakening | ||||||
| Usually (n = 397) | 8:28 (1.02)⁎⁎⁎ | 5:51 (1.11)⁎⁎⁎ | 0.70 (0.60–0.79)⁎⁎⁎ | Usually (n = 674) | 8:46 (0.99)⁎⁎⁎ | 5:35 (1.11)⁎⁎⁎ | 0.64 (0.56–0.75)⁎⁎⁎ |
| Sometimes (n = 1878) | 8:34 (0.85) | 6:55 (0.91) | 0.82 (0.74–0.89) | Sometimes (n = 2738) | 8:49 (0.81) | 6:41 (0.97) | 0.77 (0.69–0.84) |
| Never (n = 1282) | 8:32 (0.89) | 7:24 (0.87) | 0.88 (0.83–0.94) | Never (n = 1511) | 8:45 (0.84) | 7:27 (0.88) | 0.87 (0.80–0.93) |
Abbreviations: SD, standard deviation; h, hours; IQR, interquartile range.
Comparisons of time in bed and sleep duration were based on one-way analysis of variance, and comparisons of sleep proportion were based on Kruskal–Wallis test. All the P values show the overall comparisons among different levels of sleep difficulties. Time in bed and sleep duration are presented as mean (h:min) (SD [h]) and sleep proportion is presented as median (IQR). Sleep proportion = nighttime sleep duration/time in bed.
∗P < .05.
∗∗P < .01.
⁎⁎⁎
P < .001.