Table 2.
Subgroup analysis of the efficacy of light intervention on subjective alertness
| Subgroups | N | Sample size | I2 (%) | SMD (95% CI) | P-value |
|---|---|---|---|---|---|
| Parameters of light | 17 | 738 | 70 | –0.30 (–0.59, –0.01) | 0.04 |
| Wavelength | 4 | 156 | 0 | –0.13 (–0.44, 0.19) | NS |
| Correlated Color Temperature | 6 | 356 | 26 | –0.37 (–0.65, –0.10) | 0.007 |
| Illuminance | 7 | 226 | 86 | –0.40 (–1.17, 0.38) | NS |
| Timing of light intervention | 23 | 912 | 60 | –0.23 (–0.37, –0.10) | 0.0005 |
| Daytime | 15 | 690 | 74 | –0.22 (–0.37, –0.07) | 0.005 |
| Night-time | 6 | 176 | 0 | –0.32 (–0.61, –0.02) | 0.04 |
| Whole-day | 2 | 46 | 0 | –0.14 (–0.71, 0.44) | NS |
CI: Confidence interval; N: number of studies; NS: not significant; SMD: standardized mean difference.