TABLE 2.
Effects of a sleep extension intervention on outcomes of sleep duration and quality in the sleep extension group compared with the control group1
| Control group (n = 21) | Sleep extension group (n = 21) | |||||
|---|---|---|---|---|---|---|
| Baseline | Change from baseline | Baseline | Change from baseline | Mean difference | P 2 | |
| Mean 7-d actigraphy | ||||||
| Time in bed, h:mm | 7:09 (6:51, 7:28) | −0:02 (−0:19, 0:16) | 7:03 (6:45, 7:21) | 0:55 (0:37, 1:12)3 | 0:56 (0:31, 1:21) | <0.001 |
| Sleep period, h:mm | 6:54 (6:36, 7:12) | 0:05 (−0:23, 0:13) | 6:50 (6:33, 7:08) | 0:47 (0:29, 1:05)3 | 0:52 (0:27, 1:17) | <0.001 |
| Sleep duration, h:mm | 5:53 (5:36, 6:11) | −0:11 (−0:26, 0:04) | 5:28 (5:48, 6:19) | 0:21 (0:06, 0:36) | 0:32 (0:11, 0:54) | 0.004 |
| Sleep latency,4 min | 7.6 (5.3, 10.8) | 1.8 (−1.5, 5.1) | 7.7 (5.6, 9.9) | 5.7 (2.3, 9.0) | 3.9 (−0.9, 8.6) | 0.108 |
| Sleep duration,4 % | 85.0 (82.5, 87.6)5 | −0.5 (−2.4, 1.4) | 88.8 (87.3, 90.4) | −4.3 (−6.2, −2.4)3 | −3.7 (−6.5, -0.9) | 0.010 |
| Sleep efficiency,4 % | 82.0 (79.2, 84.8)5 | −1.3 (−3.1, 0.6) | 86.2 (84.6, 87.8) | −5.4 (−7.3, −3.6)3 | −4.2 (−6.9, −1.5) | 0.003 |
| SFI3 | 27.0 (22.8, 32.0)5 | −0.9 (−3.1, 1.4) | 19.9 (18.1, 21.9) | 4.0 (1.8, 6.3)3 | 4.9 (1.6, 8.3) | 0.005 |
| Sleep questionnaires | ||||||
| PSQI | 6.8 (5.2, 8.3) | 0.3 (−0.5, 1.0) | 5.2 (4.2, 6.3) | −1.1 (−1.8, −0.4)3 | −1.3 (−2.3, −0.3) | 0.013 |
| SHI | 20.9 (18.3, 23.5) | 1.0 (−1.3, 3.2) | 19 (16.3, 21.7) | −3.9 (−6.2, −1.6)3 | −4.9 (−8.1, −1.6) | 0.004 |
Values are means (95% CIs). Values presented at endpoint are estimated marginal means, adjusted for baseline. “Time in bed” indicates time from “lights out” to “got up” as indicated by participants by using an event marker button on the actigraphy device; “Sleep period” indicates time from “fell asleep” to “woke up”; “Sleep duration” indicates time spent asleep within sleep period, excluding wake time; “Sleep latency” indicates time from “lights out” to “fell asleep”; “Sleep duration” (%) indicates the proportion of time spent asleep in the sleep period; “Sleep efficiency” (%) indicates the proportion of time spent asleep of time in bed. h:mm, hours:minutes; PSQI, Pittsburgh Sleep Quality Index; SFI, Sleep Fragmentation Index; SHI, Sleep Hygiene Index.
Differences between groups in the change from baseline were tested by ANCOVA, with baseline measurements as a covariate.
Significant difference within the group; baseline and endpoint data were tested by paired-samples t test (P < 0.05).
Values are geometric means (95% CIs). Data were log-transformed before analysis.
Different from the sleep extension group at baseline, as assessed by independent-samples t test (P < 0.05).