Table 1.
Sample characteristics by Light at Night (LAN)
| Characteristic | Overall, N = 552* |
No LAN, N = 255* |
LAN, N = 297* |
p-value† | q-value‡ |
|---|---|---|---|---|---|
| Age | 72 (5) | 71 (5) | 72 (5) | 0.2 | 0.3 |
| Black | 42 (7.6%) | 7 (2.7%) | 35 (12%) | <0.001 | <0.001 |
| Female | 142 (26%) | 61 (24%) | 81 (27%) | 0.4 | 0.5 |
| Body mass index (kg/m2) | 27.9 (25.1, 31.4) | 27.5 (25.0, 30.3) | 28.5 (25.3, 32.0) | 0.010 | 0.020 |
| Season | 0.2 | 0.3 | |||
| Spring | 103 (19%) | 44 (17%) | 59 (20%) | ||
| Summer | 168 (30%) | 69 (27%) | 99 (33%) | ||
| Fall | 189 (34%) | 98 (38%) | 91 (31%) | ||
| Winter | 92 (17%) | 44 (17%) | 48 (16%) | ||
| Light variables | |||||
| 24 h mean light Intensity (lux) | 342 (97, 1,034) | 322 (97, 990) | 355 (97, 1,044) | 0.7 | 0.7 |
| 24 h median light intensity (lux) | 25 (13, 46) | 26 (14, 46) | 24 (13, 44) | 0.3 | 0.4 |
| Inter-daily stability | 0.64 (0.48, 0.74) | 0.65 (0.52, 0.74) | 0.62 (0.46, 0.73) | 0.015 | 0.027 |
| Intra-daily variability | 0.50 (0.37, 0.63) | 0.50 (0.37, 0.64) | 0.50 (0.38, 0.63) | 0.8 | 0.8 |
| Relative amplitude | 0.99 (0.97, 1.00) | 1.00 (1.00, 1.00) | 0.97 (0.90, 0.99) | <0.001 | <0.001 |
| Lowest light exposure (L5) | 0.01 (0.00, 0.05) | 0.00 (0.00, 0.00) | 0.04 (0.01, 0.14) | <0.001 | <0.001 |
| Peak light exposure (M10) | 3.1 (2.1, 4.3) | 3.0 (2.1, 4.3) | 3.1 (2.1, 4.3) | 0.4 | 0.5 |
| Lowest light (L5) midpoint | 2.8 (1.8, 3.5) | 2.5 (1.6, 3.1) | 3.1 (2.1, 3.9) | <0.001 | <0.001 |
| Peak light (M10) midpoint | 13.2 (12.5, 14.1) | 13.2 (12.5, 14.0) | 13.3 (12.6, 14.2) | 0.4 | 0.5 |
| Mean activity during L5 light | 9 (6, 14) | 7 (5, 9) | 12 (8, 18) | <0.001 | <0.001 |
| Activity variables | |||||
| Mean activity count | 97 (74, 118) | 98 (75, 118) | 96 (73, 118) | 0.6 | 0.6 |
| Inter-daily stability | 0.58 (0.51, 0.65) | 0.61 (0.54, 0.67) | 0.56 (0.48, 0.64) | <0.001 | <0.001 |
| Intra-daily variability | 0.78 (0.65, 0.93) | 0.75 (0.64, 0.90) | 0.80 (0.68, 0.94) | 0.019 | 0.033 |
| Relative amplitude | 0.90 (0.85, 0.93) | 0.92 (0.90, 0.94) | 0.87 (0.82, 0.92) | <0.001 | <0.001 |
| Lowest activity (L5) | 8 (5, 12) | 6 (4, 9) | 10 (7, 15) | <0.001 | <0.001 |
| Peak activity (M10) | 158 (121, 197) | 161 (127, 199) | 152 (119, 194) | 0.069 | 0.11 |
| Lowest activity (L5) midpoint | 2.8 (1.9, 3.7) | 2.6 (1.7, 3.4) | 3.0 (2.1, 4.0) | <0.001 | <0.001 |
| Peak activity (M10) midpoint | 13.2 (12.2, 14.1) | 13.0 (12.0, 13.9) | 13.4 (12.4, 14.5) | <0.001 | <0.001 |
| Sleep variables | |||||
| Time in bed (min) | 437 (403, 478) | 450 (416, 485) | 424 (379, 467) | <0.001 | <0.001 |
| Total sleep time (min) | 394 (351, 431) | 408 (376, 442) | 383 (335, 413) | <0.001 | <0.001 |
| Wake after sleep onset (min) | 43 (31, 59) | 40 (29, 52) | 45 (34, 65) | <0.001 | <0.001 |
| Sleep efficiency (%) | 85 (79, 88) | 87 (83, 90) | 83 (76, 87) | <0.001 | <0.001 |
| Sleep midpoint | 3.0 (2.5, 3.8) | 3.0 (2.4, 3.5) | 3.1 (2.5, 3.9) | 0.023 | 0.039 |
| Sleep onset | -0.6 (-1.3, 0.1) | -0.8 (-1.5, -0.2) | -0.5 (-1.1, 0.4) | <0.001 | <0.001 |
| Sleep offset | 6.7 (5.9, 7.4) | 6.7 (5.9, 7.4) | 6.7 (5.8, 7.4) | 0.7 | 0.7 |
*Mean (SD); n (%); median (IQR).
†Wilcoxon rank-sum test; Pearson’s χ 2 test. Bold values signify <0.05.
‡False discovery rate correction for multiple testing. Bold values signify <0.05.