Table 1.
Characteristics of the study population from the survey with and without chronic knee pain
| Variable | Without chronic knee pain n (%) |
Chronic knee pain n (%) |
P-value |
|---|---|---|---|
| Total | 6344 (79.2) | 1664 (20.8) | |
| Age (y) | 61.3 ± 8.7 | 65.2 ± 9.3 | <.0001 |
| Age, n (%) | |||
| 50–59 | 2583 (85.8) | 428 (14.2) | <.0001 |
| 60–69 | 2098 (79.4) | 543 (20.6) | |
| 70–79 | 1373 (71.8) | 539 (28.2) | |
| ≥ 80 | 290 (65.3) | 154 (34.7) | |
| Sex, n (%) | |||
| Men | 3024 (88) | 411 (12) | <.0001 |
| Women | 3320 (72.6) | 1253 (27.4) | |
| BMI (kg/m2) | 24.0 ± 3.1 | 24.7 ± 3.3 | <.0001 |
| BMI (categorical), n (%)a | |||
| Underweight (< 18.5) | 171 (83.0) | 35 (17.0) | <.0001 |
| Normal (18.5–24.9) | 3984 (81.2) | 922 (18.8) | |
| Overweight (25.0–29.9) | 1968 (76.6) | 601 (23.4) | |
| Obesity (≥30) | 221 (67.6) | 106 (32.4) | |
| Smoking status, n (%) | |||
| No | 5308 (78.4) | 1464 (21.6) | <.0001 |
| Yes | 965 (85.1) | 169 (14.9) | |
| Alcohol consumption, n (%) | |||
| None | 2333 (74.8) | 787 (25.2) | <.0001 |
| ≤ 1 drink/mo | 1037 (77.9) | 295 (22.2) | |
| 2 drinks/mo to 3 drinks/wk | 1576 (83.2) | 319 (16.8) | |
| ≥ 4 drinks/wk | 1334 (85) | 236 (15) | |
| Occupation, n (%) | |||
| Unemployed (student, housewife, etc.) | 2974 (74.7) | 1006 (25.3) | <.0001 |
| Office work | 701 (92.1) | 60 (7.9) | |
| Sales and services | 720 (85.2) | 125 (14.8) | |
| Agriculture, forestry, and fishery | 505 (75.3) | 166 (24.7) | |
| Machine fitting and simple labor | 1430 (82.6) | 302 (17.4) | |
| Household income, n (%) b | |||
| Low | 1608 (69.1) | 719 (30.9) | <.0001 |
| Mid-low | 1702 (79.8) | 431 (20.2) | |
| Mid-high | 1441 (83.3) | 289 (16.7) | |
| High | 1566 (87.9) | 216 (12.1) | |
| Education, n (%) | |||
| ≤ 6 y | 2326 (68.8) | 1057 (31.2) | <.0001 |
| 7–9 y | 1127 (80.9) | 266 (19.1) | |
| 10–12 y | 1792 (87.5) | 256 (12.5) | |
| ≥ 13 y | 1086 (93.2) | 79 (6.8) | |
| Duration of sleep (h), mean ± sd | 6.6 ± 1.4 | 6.4 ± 1.7 | <.0001 |
| Depressive symptom, n (%) c | 307 (64.6) | 168 (35.4) | <.0001 |
| Physical activity, n(%) | |||
| Low | 4083 (77.4) | 1195 (22.6) | <.0001 |
| High | 2261 (82.8) | 469 (17.2) | |
| Sedentary behaviors (h), mean ± sd | 6.5 ± 3.6 | 6.9 ± 3.8 | 0.0145 |
| Sedentary behaviors (h) d | |||
| < 5 | 2123 (33.5) | 492 (29.6) | 0.0909 |
| 5–7 | 1950 (30.7) | 498 (29.9) | |
| 8–10 | 1474 (23.2) | 415 (24.9) | |
| > 10 | 797 (12.6) | 259 (15.6) | |
BMI body mass index
Numeric parameters are expressed as means with standard deviation in parentheses, unless stated otherwise. Categorical parameters are expressed as counts with percentages in parentheses
a BMI was categorized into underweight (< 18.5 kg/m2), normal (18.5–24.9 kg/m2), overweight (25.0–29.9 kg/m2), and obesity (≥30.0 kg/m2)
b Household income levels were calculated by dividing the total household monthly income with the obtained levels then grouped into quartiles
c Depressive symptoms were defined as individuals who felt sad or experienced other depressive symptoms for 2 consecutive weeks during the past year
d Levels of sedentary behaviors were categorized using quartiles: < 5, 5–7, 8–10, and > 10 h/day