Table 2.
Objective measures of sleep quality during the intervention (blue light mask) and control (red light mask) periods.
| Total Sample (N = 46) | Mean (SD) Value | |||
| Intervention (blue light) | Control (red light) | |||
| Baseline (n = 37) | Final weeka (n = 33) | Baseline (n = 42) | Final weeka (n = 30) | |
| Wrist actigraphy | ||||
| Time in bed (min)b | 452 (71) | 460 (70) | 464 (75) | 470 (93) |
| Sleep time (min) | 354 (67) | 360 (82) | 375 (74) | 375 (93) |
| Sleep efficiency (%)c | 78.5 (12.0) | 78.8 (14.9) | 81.1 (9.8) | 80.5 (14.7) |
| Sleep bouts (n) | 17.0 (6.7) | 15.8 (9.7) | 16.1 (7.7) | 15.7 (8.2) |
| Sleep start time | 22:16 (1:13) | 22:25 (1:34) | 22:18 (1:12) | 22:19 (1:15) |
| Sleep log | ||||
| Sleep start time | 21:46 (1:07) | 21:50 (1:05) | 21:52 (1:06) | 21:50 (1:05) |
| Light mask compliant (n = 23) | Baseline (n = 23) | Final weeka (n = 21) | Baseline (n = 23) | Final weeka (n = 22) |
| Wrist actigraphy | ||||
| Time in bed (min)b | 460 (69) | 458 (77) | 462 (75) | 480 (101) |
| Sleep time (min) | 346 (62) | 348 (86) | 370 (76) | 387 (82) |
| Sleep efficiency (%)c | 75.3 (12.8) | 76.7 (16.5) | 80.1 (11.2) | 81.5 (10.6) |
| Sleep bouts (n) | 17.7 (7.3) | 16.3 (10.8) | 15.5 (8.2) | 15.4 (8.5) |
| Sleep start time | 22:22 (1:08) | 22:26 (1:32) | 22:14 (1:00) | 22:21 (0:57) |
| Sleep log | ||||
| Sleep start time | 21:43 (0:56) | 21:53 (1:03) | 21:51 (1:03) | 21:56 (1:06) |
| Light mask + Actiwatch compliant (n = 17) | Baseline (n = 17) | Final weeka (n = 16) | Baseline (n = 17) | Final weeka (n = 14) |
| Wrist actigraphy | ||||
| Time in bed (min)b | 473 (53) | 467 (67) | 465 (65) | 479 (99) |
| Sleep time (min) | 353 (65) | 331 (73) | 360 (53) | 369 (52) |
| Sleep efficiency (%)c | 74.5 (14.1) | 71.8 (16.3) | 77.6 (11.3) | 78.2 (8.8) |
| Sleep bouts (n) | 18.8 (7.4) | 18.9 (10.0) | 17.6 (7.4) | 18.3 (6.4) |
| Sleep start time | 22:27 (1:10) | 22:29 (1:42) | 22:15 (0:58) | 22:23 (1:01) |
| Sleep log | ||||
| Sleep start time | 21:44 (0:50) | 21:47 (1:05) | 21:51 (1:03) | 21:52 (1:13) |
Notes:
(a)
The final week assessments occurred during weeks 10 and 24 of the study (see Figure 2). All unadjusted differences were not statistically significant between intervention and control (p > 0.05).
(b)
Time in bed is determined by participant report.
(c)
Sleep efficiency is sleep time determined by Actiwatch divided by the time in bed determined by participant report.