Table 2.
Effects of light condition and time on mood, subjective sleepiness, task performance and visual comfort.
| Long-Wavelength Light | Short-Wavelength Light | Light | Time | Light by Time | |||||
|---|---|---|---|---|---|---|---|---|---|
| EMM (SE) | EMM (SE) | F (df) | p | F (df) | p | F (df) | p | R 2 | |
| PANAS (10–50 (extremely)) | |||||||||
| Positive mood | 19.63 (0.87) | 20.22 (0.86) | 1.13 (1, 278) | 0.289 | 56.81 (4, 267) | <0.001 | 1.57 (4, 267) | 0.182 | 0.28 |
| Negative mood | 11.55 (0.31) | 11.74 (0.31) | 0.99 (1, 278) | 0.320 | 3.93 (4, 267) | 0.004 | 3.24 (4, 267) | 0.013 | 0.05 |
| Sleepiness (KSS, 1–9 (sleepy)) | 6.97 (0.21) | 6.28 (0.21) | 25.32 (1, 278) | <0.001 | 59.23 (4, 266) | <0.001 | 3.61 (4, 266) | 0.007 | 0.30 |
| Psychomotor vigilance task | |||||||||
| Mean 1/RT | 2.82 (0.08) | 2.97 (0.08) | 18.36 (1, 272) | <0.001 | 32.21 (4, 266) | <0.001 | 3.29 (4, 266) | 0.012 | 0.14 |
| Mean RT500 | 342.79 (5.46) | 332.40 (5.44) | 25.24 (1, 270) | <0.001 | 40.97 (4, 266) | <0.001 | 4.04 (4, 266) | 0.003 | 0.14 |
| Number of lapses (RTs ≥ 500 ms) a | 6.95 (1.49) | 4.82 (1.09) | 6.60 (1, 290) | 0.011 | 37.41 (4, 290) | <0.001 | 2.68 (4, 290) | 0.032 | - |
| Digit symbol substitution test (n correct) | 73.50 (1.32) | 76.35 (1.31) | 18.17 (1, 273) | <0.001 | 8.48 (4, 265) | <0.001 | 1.58 (4, 265) | 0.180 | 0.08 |
| Headache and eye strain scale (1–4 (severe)) | |||||||||
| Irritability | 1.71 (0.12) | 1.70 (0.12) | 0.01 (1, 155) | 0.928 | 7.41 (2, 147) | 0.001 | 2.78 (2, 147) | 0.065 | 0.05 |
| Headache | 1.80 (0.11) | 1.58 (0.11) | 7.14 (1, 156) | 0.008 | 18.45 (2, 147) | <0.001 | 0.57 (2, 147) | 0.568 | 0.11 |
| Eye strain | 2.73 (0.12) | 2.44 (0.12) | 8.33 (1, 157) | 0.004 | 39.45 (2, 146) | <0.001 | 2.08 (2, 146) | 0.129 | 0.22 |
| Eye discomfort | 2.50 (0.14) | 2.22 (0.14) | 7.18 (1, 154) | 0.008 | 29.75 (2, 146) | <0.001 | 3.82 (2, 146) | 0.024 | 0.15 |
| Eye fatigue | 2.86 (0.11) | 2.49 (0.11) | 14.18 (1, 158) | <0.001 | 86.07 (2, 145) | <0.001 | 3.97 (2, 145) | 0.021 | 0.39 |
| Difficulty focusing | 2.72 (0.13) | 2.45 (0.13) | 7.72 (1, 154) | 0.006 | 56.07 (2, 145) | <0.001 | 2.05 (2, 145) | 0.132 | 0.25 |
| Difficulty concentrating | 2.74 (0.11) | 2.39 (0.11) | 11.27 (1, 160) | 0.001 | 74.03 (2, 147) | <0.001 | 1.45 (2, 147) | 0.238 | 0.38 |
| Blurred vision | 2.06 (0.14) | 1.82 (0.13) | 6.43 (1, 154) | 0.012 | 13.83 (2, 146) | <0.001 | 1.54 (2, 146) | 0.219 | 0.07 |
Note: Variables analyzed using linear mixed model analyses. a Analyzed using generalized linear mixed models. R2 is the proportion of reduction in variance of the residuals between a random effects model and the interaction effects model. EMM = estimated marginal mean; SE = standard error; df = degrees of freedom; PANAS = Positive and Negative Affect Schedule; KSS = Karolinska Sleepiness Scale; RT = response time.