Table 1 Descriptive statistic of the included variables by sex
| Â | Total | Â | Male | Â | Â | Female | Â | Â |
|---|---|---|---|---|---|---|---|---|
| Â | Normal | low BMD | Normal | low BMD | Total | Normal | low BMD | Total |
Characteristics | (N = 174,295) | (N = 20,615) | (N = 87,250) | (N = 8530) | (N = 95,780) | (N = 87,045) | (N = 12,085) | (N = 99,130) |
Age (years) | ||||||||
 Mean (SD) | 40.0 (11.4) | 53.7 (14.5) | 40.5 (11.8) | 48.2 (14.4) | 41.2 (12.3) | 39.4 (11.0) | 57.6 (13.2) | 41.6 (12.8) |
Education | ||||||||
  < 9 yr | 9257 (5.3%) | 6465 (31.4%) | 3362 (3.9%) | 1087 (12.7%) | 4449 (4.6%) | 5895 (6.8%) | 5378 (44.5%) | 11,273 (11.4%) |
 9 ~ 14 yr | 36,814 (21.1%) | 5550 (26.9%) | 16,641 (19.1%) | 2187 (25.6%) | 18,828 (19.7%) | 20,173 (23.2%) | 3363 (27.8%) | 23,536 (23.7%) |
 14 ~ 16 yr | 35,084 (20.1%) | 2892 (14.0%) | 17,033 (19.5%) | 1711 (20.1%) | 18,744 (19.6%) | 18,051 (20.7%) | 1181 (9.8%) | 19,232 (19.4%) |
 16 ~ 18 yr | 64,336 (36.9%) | 4016 (19.5%) | 31,214 (35.8%) | 2278 (26.7%) | 33,492 (35.0%) | 33,122 (38.1%) | 1738 (14.4%) | 34,860 (35.2%) |
  >  = 18 yr | 28,804 (16.5%) | 1692 (8.2%) | 19,000 (21.8%) | 1267 (14.9%) | 20,267 (21.2%) | 9804 (11.3%) | 425 (3.5%) | 10,229 (10.3%) |
Smoking status | ||||||||
 no, secondhand smoker | 142,593 (81.8%) | 17,471 (84.7%) | 61,061 (70.0%) | 5806 (68.1%) | 66,867 (69.8%) | 81,532 (93.7%) | 11,665 (96.5%) | 93,197 (94.0%) |
 ever smoker and current smoker | 31,702 (18.2%) | 3144 (15.3%) | 26,189 (30.0%) | 2724 (31.9%) | 28,913 (30.2%) | 5513 (6.3%) | 420 (3.5%) | 5933 (6.0%) |
Physical activity (intensity) | ||||||||
 light exercise | 125,164 (71.8%) | 16,965 (82.3%) | 51,407 (58.9%) | 6143 (72.0%) | 57,550 (60.1%) | 73,757 (84.7%) | 10,822 (89.5%) | 84,579 (85.3%) |
 mean exercise | 36,417 (20.9%) | 2660 (12.9%) | 25,823 (29.6%) | 1651 (19.4%) | 27,474 (28.7%) | 10,594 (12.2%) | 1009 (8.3%) | 11,603 (11.7%) |
 heavy or violent exercise | 12,714 (7.3%) | 990 (4.8%) | 10,020 (11.5%) | 736 (8.6%) | 10,756 (11.2%) | 2694 (3.1%) | 254 (2.1%) | 2948 (3.0%) |
Sleep score | ||||||||
 Mean (SD) | 6.97 (1.33) | 6.68 (1.54) | 7.14 (1.29) | 6.99 (1.36) | 7.13 (1.30) | 6.79 (1.34) | 6.47 (1.62) | 6.75 (1.38) |
Milk | ||||||||
 no; < 1 cup/wk | 95,666 (54.9%) | 11,364 (55.1%) | 49,457 (56.7%) | 5068 (59.4%) | 54,525 (56.9%) | 46,209 (53.1%) | 6296 (52.1%) | 52,505 (53.0%) |
  >  = 1 cup/wk | 78,629 (45.1%) | 9251 (44.9%) | 37,793 (43.3%) | 3462 (40.6%) | 41,255 (43.1%) | 40,836 (46.9%) | 5789 (47.9%) | 46,625 (47.0%) |
Dairy | ||||||||
 no; < 1 slice of yogurt or cheese/wk | 100,280 (57.5%) | 14,107 (68.4%) | 51,295 (58.8%) | 5642 (66.1%) | 56,937 (59.4%) | 48,985 (56.3%) | 8465 (70.0%) | 57,450 (58.0%) |
  >  = 1 slice of yogurt or cheese/wk | 74,015 (42.5%) | 6508 (31.6%) | 35,955 (41.2%) | 2888 (33.9%) | 38,843 (40.6%) | 38,060 (43.7%) | 3620 (30.0%) | 41,680 (42.0%) |
Vegetarian | ||||||||
 Yes | 4193 (2.4%) | 1153 (5.6%) | 1547 (1.8%) | 279 (3.3%) | 1826 (1.9%) | 2646 (3.0%) | 874 (7.2%) | 3520 (3.6%) |
 No | 170,102 (97.6%) | 19,462 (94.4%) | 85,703 (98.2%) | 8251 (96.7%) | 93,954 (98.1%) | 84,399 (97.0%) | 11,211 (92.8%) | 95,610 (96.4%) |
BMI | ||||||||
 normal | 93,404 (53.6%) | 12,064 (58.5%) | 37,746 (43.3%) | 4994 (58.5%) | 42,740 (44.6%) | 55,658 (63.9%) | 7070 (58.5%) | 62,728 (63.3%) |
 underweight | 12,154 (7.0%) | 1899 (9.2%) | 1760 (2.0%) | 624 (7.3%) | 2384 (2.5%) | 10,394 (11.9%) | 1275 (10.6%) | 11,669 (11.8%) |
 overweight | 41,883 (24.0%) | 4491 (21.8%) | 29,052 (33.3%) | 2032 (23.8%) | 31,084 (32.5%) | 12,831 (14.7%) | 2459 (20.3%) | 15,290 (15.4%) |
 obesity | 26,854 (15.4%) | 2161 (10.5%) | 18,692 (21.4%) | 880 (10.3%) | 19,572 (20.4%) | 8162 (9.4%) | 1281 (10.6%) | 9443 (9.5%) |
Waistline | ||||||||
 central obesity | 28,355 (16.3%) | 3668 (17.8%) | 17,903 (20.5%) | 1121 (13.1%) | 19,024 (19.9%) | 10,452 (12.0%) | 2547 (21.1%) | 12,999 (13.1%) |
 normal | 145,940 (83.7%) | 16,947 (82.2%) | 69,347 (79.5%) | 7409 (86.9%) | 76,756 (80.1%) | 76,593 (88.0%) | 9538 (78.9%) | 86,131 (86.9%) |
Triglyceride | ||||||||
  >  = 150 mg/dl | 36,338 (20.8%) | 5022 (24.4%) | 27,111 (31.1%) | 2366 (27.7%) | 29,477 (30.8%) | 9227 (10.6%) | 2656 (22.0%) | 11,883 (12.0%) |
 normal | 137,957 (79.2%) | 15,593 (75.6%) | 60,139 (68.9%) | 6164 (72.3%) | 66,303 (69.2%) | 77,818 (89.4%) | 9429 (78.0%) | 87,247 (88.0%) |
Uric acid | ||||||||
 hyperuricemia | 43,642 (25.0%) | 4579 (22.2%) | 33,210 (38.1%) | 2323 (27.2%) | 35,533 (37.1%) | 10,432 (12.0%) | 2256 (18.7%) | 12,688 (12.8%) |
 normal | 130,653 (75.0%) | 16,036 (77.8%) | 54,040 (61.9%) | 6207 (72.8%) | 60,247 (62.9%) | 76,613 (88.0%) | 9829 (81.3%) | 86,442 (87.2%) |
Walkability (park and elementary school; 1Â km buffer) | ||||||||
 Mean (SD) | 5.88 (6.90) | 5.25 (6.54) | 5.75 (6.81) | 5.26 (6.64) | 5.71 (6.79) | 6.00 (6.99) | 5.25 (6.47) | 5.91 (6.93) |
Solar radiation | ||||||||
 Mean (SD) | 13.5 (1.64) | 13.6 (1.63) | 13.5 (1.64) | 13.6 (1.61) | 13.5 (1.64) | 13.5 (1.65) | 13.6 (1.64) | 13.5 (1.65) |