Table 2.
Seasonal characteristics of study population.
| Characteristic | Season and Occupation | |||||
|---|---|---|---|---|---|---|
| Summer (n = 160) | Winter (n = 160) | |||||
| Indoor (n = 80) | Outdoor (n = 80) | p | Indoor (n = 80) | Outdoor (n = 80) | p | |
| Serum [25(OH)D], ng/mL | 21.3 ± 8.5 | 23.6 ± 7.2 | 0.010 | 7.6 ± 3.2 | 7.9 ± 3.0 | 0.52 |
| Body surface area exposed, % | 32.9 ± 14.5 | 33.0 ± 14.4 | 0.94 | 17.4 ± 12.2 | 14.9 ± 8.7 | 0.045 |
| Exposure duration score 1 | 11.1 ± 8.2 | 23.9 ± 6.8 | <0.001 | 11.9 ± 7.2 | 17.8 ± 9.9 | <0.001 |
| Sun-exposure behaviors 2 | ||||||
| Used a brimmed hat | 83 (58) | 102 (81) | <0.001 | 101 (70) | 119 (77) | 0.16 |
| Used sunscreen | 27 (24) | 15 (16) | 0.14 | 15 (21) | 13 (16) | 0.46 |
| Used makeup 3 | 54 (77) | 37 (63) | 0.07 | 57 (76) | 48 (62) | 0.05 |
| Experienced sunburn | 115 (81) | 95 (78) | 0.53 | 71 (54) | 70 (47) | 0.23 |
| At least 100 IU/day of vitamin D from 4 | ||||||
| Fish | 1 (1) | 0 (0) | 1.00 | 0 (0) | 0 (0) | 0.28 |
| Eggs | 0 (0) | 1 (1) | 0.08 | 2 (3) | 0 (0) | 1.00 |
| Organ meats | 0 (0) | 0 (0) | 1.00 | 0 (0) | 0 (0) | 1.00 |
| Total IU/day from fish, eggs, organs 4 | 24.5 ± 30.6 | 15.4 ± 28.8 | 0.41 | 33.1 ± 37.2 | 17.5 ± 23.7 | 0.015 |
| Supplement use 2 | <0.001 | 0.36 | ||||
| Multivitamin | 15 (13) | 0 (0) | 9 (6) | 7 (6) | ||
| Vitamin D | 1 (1) | 0 (0) | 5 (4) | 1 (1) | ||
| Other or unspecified | 13 (11) | 17 (14) | 13 (9) | 17 (14) | ||
| None | 89 (75) | 103 (86) | 113 (81) | 100 (80) | ||
| Milk consumption, cups/day 5 | ||||||
| Manufactured milk, Mongolian | 0.4 ± 0.4 | 0.8 ± 0.8 | 0.003 | 0.4 ± 0.6 | 0.4 ± 0.5 | 0.91 |
| Manufactured milk, imported | 0.1 ± 0.2 | 0.1 ± 0.2 | 0.27 | 0.0 ± 0.0 | 0.0 ± 0.1 | 0.48 |
| Fresh cow milk | 0.5 ± 0.4 | 1.4 ± 0.6 | <0.001 | 0.3 ± 0.5 | 0.7 ± 0.6 | <0.001 |
| Source of cooking flour | 0.39 | 0.65 | ||||
| Always Mongolian | 46 (79) | 53 (88) | 58 (70) | 51 (75) | ||
| Mostly Mongolian | 7 (12) | 4 (7) | 15 (18) | 11 (16) | ||
| Half Mongolian, half imported | 4 (7) | 2 (3) | 8 (10) | 5 (7) | ||
| Mostly imported | 1 (2) | 0 (0) | 0 (0) | 1 (1) | ||
| Always imported | 0 (0) | 1 (2) | 2 (2) | 0 (0) | ||
Values are n (%) or means ± SDs. Percentages are calculated after excluding missing values. p values are drawn from tests of differences between occupations within the same seasons. 1 Range of exposure duration score: 0 to 28; 2 Sun-exposure behaviors and supplement use are assessed as “Ever during past six months”; 3 Makeup use assessed in females only; 4 IU: international unit; 5 Cup volume: 240 mL.