Table 1 Demographic characteristics of the study participants
Variables | Male, N = 252 N (%) | Female, N = 301 N (%) | All, N = 553 N (%) |
|---|---|---|---|
Age, mean + SD (years) | 49.8 + 11.7 | 51.3 + 9.4 | 50.6 + 10.5 |
 <  40 | 55 (21.8) | 37 (12.3) | 92 (16.6) |
 40~ < 50 | 51 (20.2) | 71 (23.6) | 122 (22.1) |
 50~ < 60 | 95 (37.7) | 142 (47.2) | 237 (42.9) |
>  60 | 51 (20.2) | 51 (16.9) | 102 (18.4) |
BMI, mean + SD (kg/m2) | 25.6 + 3.1 | 24.1 + 3.8 | 24.8 + 3.5 |
 <  24 | 73 (29.0) | 151 (50.2) | 224 (40.5) |
 24~ <  27 | 103 (40.8) | 93 (30.9) | 196 (35.4) |
>  27 | 76 (30.2) | 57 (18.9) | 133 (24.1) |
Lifetime work tenure (years) | |||
 <  15 | 59 (23.4) | 76 (25.2) | 135 (24.4) |
 15~ < 30 | 82 (32.5) | 127 (42.2) | 209 (37.8) |
>  30 | 111 (44.0) | 97 (32.3) | 208 (37.7) |
 missing | 0 (0.0) | 1 (0.3) | 1 (0.1) |
Low back pain (within 6 months) | 211 (84.1) | 246 (83.1) | 457 (83.6) |
Cigarette smoking (pack-years) | |||
 0 | 138 (54.7) | 288 (95.7) | 426 (77.0) |
 1~ <  20 | 43 (17.1) | 13 (4.3) | 56 (10.1) |
>  20 | 70 (27.9) | 0 (0.1) | 70 (12.7) |
 missing | 1 (0.3) | 0 (0.0) | 1 (0.2) |
Exercisea (Yes) | 171 (67.9) | 185 (62.5) | 356 (65.0) |