Table 1.
Bed, sleep, wake and rise times for each laboratory study night.
Figure 1.
Protocol schematic. BL: baseline; MEM: Williams word memory test; POMS: Profile Of Mood States; SLT: sleep latency test; SSS: Stanford Sleepiness Scale; WAVT: Wilkinson auditory vigilance task.
Table 2.
Sleep variables for each study night.
| N | R | NC | RC | NE | RE | |
|---|---|---|---|---|---|---|
| TIB | 510 | 390 | 510 | 510 | 660 | 660 |
| TST | 489 (19)bf | 383 (8)i | 491 (11)bf | 493 (15)bf | 620 (40)abc | 625 (22)abc |
| Stage 1 | 35 (16)bh | 18 (7)i | 32 (14)bf | 28 (14)bf | 41 (18)bc | 47 (20)abc |
| Stage 2 | 264 (33)bf | 202 (24)i | 267 (27)bf | 256 (16)bf | 334 (42)abc | 317 (32)abc |
| SWS | 83 (27)h | 76 (26)ef | 83 (21)h | 86 (28)b | 89 (28)b | 96 (31)abd |
| REM | 101 (22)bf | 83 (21)i | 101 (18)bef | 116 (20)i | 148 (18)abc | 157 (34)abc |
| REM Periods (n) | 4.8 (0.9)bf | 4 (0.9)i | 4.7 (0.9)bf | 4.9 (0.6)bf | 6.7 (1.1)abc | 6.6 (1.2)abc |
| SOL | 9 (9)b | 4 (2)adg | 13 (10)bhd | 5h (3)h | 10b (10)b | 7 (5)d |
| WASO | 12 (18)bh | 4 (6)af | 6 (4)f | 10 (15)h | 19 (20)bd | 23 (21)abc |
1 Notes: Data are presented as means (± SD) in minutes, except for number of REM periods. TIB: time-in-bed (time allowed for sleep only); TST: total sleep time; SWS: slow wave sleep; REM: rapid eye movement; SOL: sleep onset latency; WASO: wake after sleep onset. N: baseline nominal (mean of two nights); R: baseline restricted (mean of two nights); NC: experimental control night following baseline nominal; RC: experimental control night following baseline restricted; NE: experimental extended night following baseline nominal; RE: experimental extended night following baseline restricted. Significant difference (p<0.05) from: aN, bR, cNC/RC, dNC, eRC, fNE/RE, gNE, hRE, iall other conditions.
Table 3.
Sleepiness, mood and performance for each experimental condition.
| NC | RC | NE | RE | |
|---|---|---|---|---|
| MSLT (min) | 10.1 (7.4)a | 9.4 (6.9)b | 14.2 (6.6) | 13.3 (7.1) |
| SSS | 2.9 (0.7) | 3.0 (0.9) | 2.8 (0.8) | 2.8 (0.7) |
| POMS Fatigue | 3.7 (4.0) | 4.3 (4.3)b | 3.3 (3.1) | 2.4 (2.6) |
| POMS Vigor | 7.2 (5.8)a | 6.6 (5.9)b | 9.0 (6.2) | 8.9 (6.6) |
| WAVT (No. missed) | 1.6 (2.5) | 1.4 (2.0) | 1.3 (1.7) | 1.0 (1.0) |
| MEM (No. correct) | 15.0 (4.1) | 14.1 (4.3) | 14.6 (4.9) | 14.8 (5.1) |
1 Notes: Data are means (± SD). MSLT: multiple sleep latency test; SSS: Stanford Sleepiness Scale; POMS: Profile of Mood States; WAVT: Wilkinson auditory vigilance task; MEM: Williams word memory task. NC: experimental control night following baseline nominal; RC: experimental control night following baseline restricted; NE: experimental extended night following baseline nominal; RE: experimental extended night following baseline restricted. Significant difference (p<0.05) from: aNE, bRE.
Figure 2.
Mean (± SEM) values for MSLT and neurobehavioural outcomes across time-of-day for each condition. Some scales reversed so that all panels show higher alertness and performance in upwards direction. NC: experimental control night following baseline nominal; RC: experimental control night following baseline restricted; NE: experimental extended night following baseline nominal; RE: experimental extended night following baseline restricted.
Table 4.
Results from the linear mixed-effects ANOVA for neurobehavioural outcomes.
| Planned comparisons (p-values) | ||||||
|---|---|---|---|---|---|---|
| df | F | P | NC v NE | RC v RE | NE v RE | |
| MSLT | ||||||
| Condition | 3,152 | 11.779 | <0.001 | <0.001 | <0.001 | 0.311 |
| Time-of-day | 4,152 | 22.318 | <0.001 | |||
| Cond*Time | 12,152 | 1.384 | 0.179 | |||
| SSS | ||||||
| Condition | 3,152 | 1.620 | 0.187 | - | - | - |
| Time-of-day | 4,152 | 3.111 | 0.017 | |||
| Cond*Time | 12,152 | 0.525 | 0.896 | |||
| POMS Fatigue | ||||||
| Condition | 3,120 | 3.917 | 0.010 | 0.510 | 0.001 | 0.122 |
| Time-of-day | 3,120 | 7.575 | <0.001 | |||
| Cond*Time | 9,120 | 1.172 | 0.319 | |||
| POMS Vigor | ||||||
| Condition | 3,120 | 4.366 | 0.006 | 0.030 | 0.006 | 0.919 |
| Time-of-day | 3,120 | 3.256 | 0.024 | |||
| Cond*Time | 9,120 | 1.278 | 0.256 | |||
| WAVT | ||||||
| Condition | 3,120 | 0.873 | 0.457 | - | - | - |
| Time-of-day | 3,120 | 3.002 | 0.033 | |||
| Cond*Time | 9,120 | 0.999 | 0.445 | |||
| MEM | ||||||
| Condition | 3,120 | 0.440 | 0.725 | - | - | - |
| Time-of-day | 3,120 | 0.185 | 0.906 | |||
| Cond*Time | 9,120 | 0.279 | 0.979 | |||
1 Notes: MSLT: multiple sleep latency test; SSS: Stanford Sleepiness Scale; POMS: Profile of Mood States; WAVT: Wilkinson auditory vigilance task; MEM: Williams word memory task. NC: experimental control night following baseline nominal; RC: experimental control night following baseline restricted; NE: experimental extended night following baseline nominal; RE: experimental extended night following baseline restricted.
Figure 3.
Change in objective (MSLT) and subjective (SSS) sleepiness after extended sleep (NE) compared to control sleep (NC) (both nights following nominal baseline sleep) for each participant.
Note: Change in SSS is displayed as the inverse so that a positive change in both measures represents a reduction in sleepiness. Closed circles represent change in MSLT in minutes; open circles represent change in SSS in scale units. Figure shows that: a) objective and subjective measures do not correlate; b) objective sleepiness was reduced under conditions of sleep extension for all participants; and c) participants varied as to whether they rated their sleepiness as reduced following sleep extension.
