Table 1. Baseline characteristics of study participants according to hours of sunlight exposure.
| Characteristics | Total (%) | p-value | Male (%) | p-value | Female (%) | p-value | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| Lowa | Highb | Low | High | Low | High | |||||
| Total participants | 9,198 (78.1) | 2,577 (21.9) | - | 4,761 (75.0) | 1,591 (25.0) | < 0.001 | 4,437 (81.8) | 986 (18.2) | < 0.001 | |
| Age (years) | < 0.001 | < 0.001 | - | |||||||
| < 40 | 3,310 (83.4) | 658 (16.6) | 1,705 (80.2) | 421 (19.8) | 1,605 (87.1) | 237 (12.9) | ||||
| 40–59 | 4,374 (79.9) | 1,102 (20.1) | 2,253 (76.7) | 685 (23.3) | 2,121 (83.6) | 417 (16.4) | ||||
| ≥ 60 | 1,514 (65.0) | 817 (35.0) | 803 (62.3) | 485 (37.7) | 711 (68.2) | 332 (31.8) | ||||
| Household income | < 0.001 | < 0.001 | < 0.001 | |||||||
| Low | 1,121 (68.7) | 511 (31.3) | 468 (64.5) | 258 (35.5) | 653 (72.1) | 253 (28.0) | ||||
| Low-middle | 2,183 (75.0) | 729 (25.0) | 1,115 (70.3) | 471 (29.7) | 1,068 (80.5) | 258 (19.5) | ||||
| Middle-high | 2,893 (80.1) | 717 (19.9) | 1,537 (76.5) | 472 (23.5) | 1,356 (84.7) | 245 (15.3) | ||||
| High | 3,001 (82.3) | 620 (17.1) | 1,641 (80.8) | 390 (19.2) | 1,360 (85.5) | 230 (14.5) | ||||
| Education level | < 0.001 | < 0.001 | < 0.001 | |||||||
| Less than elementary school | 1,651 (68.4) | 762 (31.6) | 573 (63.6) | 328 (36.4) | 1,078 (71.3) | 434 (28.7) | ||||
| Middle school | 1,011 (73.1) | 373 (27.0) | 514 (68.1) | 241 (31.9) | 497 (79.0) | 132 (21.0) | ||||
| High school | 3,260 (79.6) | 834 (20.4) | 1,718 (74.4) | 590 (25.6) | 1,542 (86.3) | 244 (13.7) | ||||
| College or higher | 3,276 (84.4) | 608 (15.7) | 1,956 (81.2) | 432 (18.1) | 1,320 (88.2) | 176 (11.8) | ||||
| Occupational classification | < 0.001 | < 0.001 | < 0.001 | |||||||
| White collar | 3,414 (86.0) | 558 (14.0) | 1,855 (84.3) | 345 (15.7) | 1,559 (88.0) | 213 (12.0) | ||||
| Pink collar | 2,071 (81.9) | 458 (18.1) | 769 (76.1) | 242 (23.9) | 1,302 (85.8) | 216 (14.2) | ||||
| Green collar | 1,037 (59.2) | 716 (40.8) | 526 (56.7) | 402 (43.3) | 511 (61.9) | 314 (38.1) | ||||
| Blue collar | 2,676 (76.0) | 845 (24.0) | 1,611 (72.8) | 602 (27.2) | 1,065 (81.4) | 243 (18.6) | ||||
| Alcohol consumption | 0.055 | 0.077 | 0.003 | |||||||
| None | 1,836 (76.7) | 559 (23.3) | 573 (71.8) | 225 (28.2) | 1,263 (79.1) | 334 (20.9) | ||||
| Moderate | 6,018 (78.8) | 1,621 (21.2) | 3,079 (75.2) | 1,015 (24.8) | 2,939 (82.9) | 606 (17.1) | ||||
| High-risk | 1,344 (77.2) | 397 (22.8) | 1,109 (76.0) | 351 (24.0) | 235 (83.6) | 46 (16.4) | ||||
| Current smoking | < 0.001 | 0.169 | 0.431 | |||||||
| No | 6,802 (79.3) | 1,780 (20.7) | 2,623 (75.6) | 845 (24.4) | 4,179 (81.7) | 935 (18.3) | ||||
| Yes | 2,396 (75.0) | 797 (25.0) | 2,138 (74.1) | 746 (25.9) | 258 (83.5) | 51 (16.5) | ||||
| Physical activity | 0.011 | 0.018 | 0.001 | |||||||
| No | 5,752 (77.5) | 1,670 (22.5) | 2,598 (73.7) | 925 (26.3) | 3,154 (80.9) | 745 (19.1) | ||||
| Moderate | 2,909 (78.6) | 792 (21.4) | 1,836 (76.0) | 580 (24.0) | 1,073 (83.5) | 212 (16.5) | ||||
| High | 537 (82.4) | 115 (17.6) | 327 (79.2) | 86 (20.8) | 210 (87.9) | 29 (12.1) | ||||
| Obesity (BMI, kg/m2) | 0.002 | 0.979 | < 0.001 | |||||||
| Underweight (< 18.5) | 378 (79.1) | 100 (20.9) | 130 (75.1) | 43 (24.9) | 248 (81.3) | 57 (18.7) | ||||
| Normal | 5,922 (79.0) | 1,569 (21.0) | 2,880 (74.9) | 967 (25.1) | 3,042 (83.5) | 602 (16.5) | ||||
| Overweight (≥ 25.0) | 2,898 (76.1) | 908 (23.9) | 1,751 (75.1) | 581 (24.9) | 1,147 (77.8) | 327 (22.2) | ||||
| Hypertension | < 0.001 | < 0.001 | < 0.001 | |||||||
| No | 6,802 (80.3) | 1,669 (19.7) | 3,275 (76.7) | 997 (23.3) | 3,527 (84.0) | 672 (16.0) | ||||
| Yes | 2,396 (72.5) | 908 (27.5) | 1,486 (71.4) | 594 (28.6) | 910 (74.4) | 314 (25.6) | ||||
| Diabetes mellitus | < 0.001 | < 0.001 | < 0.001 | |||||||
| No | 8,556 (78.9) | 2,292 (21.1) | 4,356 (75.8) | 1,394 (24.2) | 4,200 (82.4) | 898 (17.6) | ||||
| Yes | 642 (69.3) | 285 (30.7) | 405 (67.3) | 197 (32.7) | 237 (72.9) | 88 (27.1) | ||||
| Cataract | < 0.001 | < 0.001 | < 0.001 | |||||||
| No | 7,123 (80.7) | 1,702 (19.3) | 3,661 (77.4) | 1,071 (22.6) | 3,462 (84.6) | 631 (15.4) | ||||
| Yes | 2,075 (70.3) | 875 (29.7) | 1,100 (67.9) | 520 (32.1) | 975 (73.3) | 355 (26.7) | ||||
| Pterygium | < 0.001 | 0.004 | < 0.001 | |||||||
| No | 8,658 (78.9) | 2,320 (21.1) | 4,462 (75.4) | 1,458 (24.6) | 4,196 (83.0) | 862 (17.0) | ||||
| Yes | 540 (67.8) | 257 (32.2) | 299 (69.2) | 133 (30.8) | 241 (66.0) | 124 (34.0) | ||||
| AMD | < 0.001 | < 0.001 | < 0.001 | |||||||
| No | 8,900 (78.8) | 2,390 (21.2) | 4,589 (75.6) | 1,478 (24.4) | 4,311 (82.5) | 912 (17.5) | ||||
| Yes | 298 (61.4) | 187 (38.6) | 172 (60.4) | 113 (39.6) | 126 (63.0) | 74 (37.0) | ||||
Bold-faced values are statistically significant (p < 0.05).
BMI: body mass index; AMD: age-related macular degeneration.
aLow: Less than 5 hours of sunlight exposure; bHigh: More than 5 hours of sunlight exposure.