Table 1. Sample characteristics by baseline level of physical function (WOMAC Function Subscale Quartiles).
| WOMAC Function Quartile | ||||||
| Participant Characteristic | Overall(N = 2156) | 1st (leastaffected)(N = 502) | 2nd (N = 530) | 3rd (N = 557) | 4th (mostaffected)(N = 567) | P-value* |
| Demographics (Baseline Assessment) | ||||||
| Age: mean (SD) | 71.3 (9.2) | 70.4 (8.9) | 70.4 (8.7) | 72.0 (9.0) | 72.1 (10.1) | <0.001 |
| Age category: N (%) | <0.001 | |||||
| 55–64 | 591 (27.4%) | 150 (29.9%) | 148 (27.9%) | 133 (23.9%) | 160 (28.2%) | |
| 65–74 | 767 (35.6%) | 192 (38.3%) | 220 (41.5%) | 194 (34.8%) | 161 (28.4%) | |
| 75+ | 798 (37.0%) | 160 (31.9%) | 162 (30.6%) | 230 (41.3%) | 246 (43.4%) | |
| Sex: N (%) female | 1,552 (72.0%) | 348 (69.3%) | 366 (69.1%) | 401 (72.0%) | 437 (77.1%) | 0.01 |
| Income: N (%) | <0.001 | |||||
| ≤ $20,000 | 1,132 (52.5%) | 220 (43.8%) | 251 (47.4%) | 293 (52.6%) | 368 (64.9%) | |
| > $20,000 | 649 (30.1%) | 198 (39.4%) | 187 (35.3%) | 163 (29.3%) | 101 (17.8%) | |
| Missing | 375 (17.4%) | 84 (16.7%) | 92 (17.4%) | 101 (18.1%) | 98 (17.3% | |
| Education: N (%) | <0.001 | |||||
| Less than high school completion | 778 (36.1%) | 145 (28.9%) | 161 (30.4%) | 221 (39.7%) | 251 (44.3%) | |
| Completed high school | 1,013 (47.0%) | 247 (49.2%) | 263 (49.6%) | 266 (47.8%) | 237 (41.8%) | |
| Some post-secondary education | 327 (15.2%) | 105 (20.9%) | 100 (18.9%) | 60 (10.8%) | 62 (10.9%) | |
| Missing | 38 (1.8%) | 5 (1.0%) | 6 (1.1%) | 10 (1.8%) | 17 (3.0%) | |
| Living arrangements: N (%) | 0.02 | |||||
| Living with others | 1,425 (66.1%) | 350 (69.7%) | 374 (70.6%) | 360 (64.6%) | 341 (60.1%) | |
| Living alone | 671 (31.1%) | 138 (27.5%) | 145 (27.4%) | 183 (32.9%) | 205 (36.2%) | |
| In long-term care | 33 (1.5%) | 9 (1.8%) | 5 (0.9%) | 7 (1.3%) | 12 (2.1%) | |
| Missing | 27 (1.3%) | 5 (1.0%) | 6 (1.1%) | 7 (1.3%) | 9 (1.6%) | |
| Place of residence: N (%) urban | 942 (43.7%) | 271 (44.0%) | 225 (42.5%) | 225 (40.4%) | 271 (47.8%) | 0.08 |
| Health-Related Variables (Baseline Assessment) | ||||||
| Pre-existing CVD (self-reported ordocumented in the administrative data): N (%) | 854 (39.6%) | 159 (31.7%) | 188 (35.5%) | 233 (41.8%) | 274 (48.3%) | <0.001 |
| Diabetes (self reported or documentedin the administrative data): N (%) | 440 (20.4%) | 87 (17.3%) | 95 (17.9%) | 114 (20.5%) | 144 (25.4%) | 0.003 |
| Hypertension (self reported ordocumented in the administrative data):N (%) | 1,369 (63.5%) | 302 (60.2%) | 323 (60.9%) | 366 (65.7%) | 378 (66.7%) | 0.06 |
| Depression (SF36 mental health subscale):N (%) | 621 (28.8%) | 83 (16.5%) | 123 (23.2%) | 154 (27.7%) | 261 (46.0%) | <0.001 |
| No. other comorbid conditions (self reported):N (%) | <0.001 | |||||
| 0 | 84 (3.9%) | 37 (7.4%) | 19 (3.6%) | 12 (2.2%) | 16 (2.8%) | |
| 1 | 390 (18.1%) | 128 (25.5%) | 101 (19.1%) | 105 (18.9%) | 56 (9.9%) | |
| 2 | 678 (31.5%) | 176 (35.1%) | 178 (33.6%) | 186 (33.4%) | 138 (24.3%) | |
| 3+ | 1,004 (46.6%) | 161 (32.1%) | 232 (43.8%) | 254 (45.6%) | 357 (63.0%) | |
| Frailty: N (%) | 54 (2.5%) | 12 (2.4%) | 7 (1.3%) | 16 (2.9%) | 19 (3.4%) | 0.17 |
| Body mass index (BMI): N (%) | 0.007 | |||||
| Underweight | 36 (1.7%) | 5 (1.0%) | 6 (1.1%) | 12 (2.2%) | 13 (2.3%) | |
| Normal | 546 (25.4%) | 152 (30.3%) | 127 (24.0%) | 148 (26.6%) | 119 (21.0%) | |
| Overweight | 761 (35.3%) | 181 (36.1%) | 200 (37.7%) | 188 (33.8%) | 192 (33.9%) | |
| Obese | 683 (31.7%) | 136 (27.1%) | 174 (32.8%) | 170 (30.5%) | 203 (35.8%) | |
| Missing | 130 (6.0%) | 28 (5.6%) | 23 (4.3%) | 39 (7.0%) | 40 (7.1%) | |
| Smoking history: N (%) | 0.55 | |||||
| Never smoked | 1,012 (46.9%) | 231 (46.0%) | 239 (45.1%) | 270 (48.5%) | 272 (48.0%) | |
| Former smoker | 783 (36.3%) | 194 (38.7%) | 197 (37.2%) | 205 (36.8%) | 187 (33.0%) | |
| Current smoker | 312 (14.5%) | 67 (13.4%) | 81 (15.3%) | 72 (12.9%) | 92 (16.2%) | |
| Missing | 49 (2.3%) | 10 (2.0%) | 13 (2.5%) | 10 (1.8%) | 16 (2.8%) | |
| Number of visits to a general practitioner inpre-baseline year: median (inter-quartilerange) | 6 (3–11) | 6 (2–10) | 5 (3–10) | 6 (3–11) | 8 (4–12) | <0.001 |
| Number of visits to a specialist in pre-baselineyear: median (inter-quartile range) | 2 (1–6) | 2 (1–6) | 2 (0–5) | 2 (1–6) | 3 (1–7) | 0.005 |
| Continuity of Care Index (range is from 0 to 1) | 0.90 (0.74–1.0) | 0.90 (0.71–1.0) | 0.93 (0.76–1.0) | 0.90 (0.72–1.0) | 0.89 (0.74–1.0) | 0.03 |
| Osteoarthritis-Related Variables | ||||||
| Use of aid for walking: N (%) | 953 (44.2%) | 130 (25.9%) | 179 (33.8%) | 267 (47.9%) | 377 (66.5%) | <0.001 |
| HAQ walking score (/3): median (IQR) | 2 (0–2) | 0 (0–2) | 1 (0–2) | 2 (1–2) | 2 (2–2) | <0.0001 |
| WOMAC pain quartile: N (%) | <0.001 | |||||
| 1st (least pain) | 460 (21.3%) | 317 (63.2%) | 97 (18.3%) | 33 (5.9%) | 13 (2.3%) | |
| 2nd | 435 (20.2%) | 116 (23.1%) | 210 (39.6%) | 92 (16.5%) | 17 (3.0%) | |
| 3rd | 627 (29.2%) | 59 (11.8%) | 172 (32.5%) | 262 (47.0%) | 134 (23.6%) | |
| 4th (most pain) | 627 (29.2%) | 7 (1.4%) | 49 (9.3%) | 169 (30.3%) | 402 (70.9%) | |
| Missing | 7 (0.3%) | 3 (0.6%) | 2 (0.4%) | 1 (0.2%) | 1 (0.2%) | |
| Non-ASA NSAID use (self-report): N (%) | 816 (37.9%) | 163 (32.5%) | 222 (41.9%) | 211 (37.9%) | 220 (38.8%) | 0.02 |
| Number of troublesome hips/knees: N (%) | <0.001 | |||||
| 0 | 84 (3.9%) | 44 (8.8%) | 21 (4.0%) | 9 (1.6%) | 10 (1.8%) | |
| 1 | 310 (14.4%) | 101 (20.1%) | 94 (17.7%) | 77 (13.8%) | 38 (6.7%) | |
| 2 | 786 (36.5%) | 179 (35.7%) | 199 (37.6%) | 213 (38.2%) | 195 (34.4%) | |
| 3 | 249 (11.6%) | 39 (7.8%) | 59 (11.1%) | 75 (13.5%) | 76 (13.4%) | |
| 4 | 454 (21.1%) | 35 (7.0%) | 103 (19.4%) | 109 (19.6%) | 207 (36.5%) | |
| Missing | 273 (12.7%) | 104 (20.7%) | 54 (10.2%) | 74 (13.3%) | 41 (7.2%) | |
| Follow-up Time and Outcomes | ||||||
| Follow-up time until death or censoring (years):median (inter-quartile range) | 13.2 (6.3–15.5) | 13.9 (7.5–15.5) | 13.9 (7.8–15.6) | 13.0 (5.8–15.5) | 10.6 (5.0–15.3) | <0.001 |
| Outcome of death: N (%) | 1,236 (57.3%) | 269 (21.8%) | 265 (21.4%) | 331 (26.8%) | 371 (30.0%) | <0.001 |
| Follow-up time until composite CVDoutcome or censoring): median (inter-quartilerange) | 9.2 (3.7–15.0) | 10.5 (4.8–15.2) | 10.6 (4.7–15.4) | 8.8 (3.3–14.9) | 6.9 (3.1–14.6) | <0.001 |
| CVD-related hospital admission orED visit: N (%) | 822 (38.1%) | 182 (36.3%) | 189 (35.7%) | 213 (38.2%) | 238 (42.0%) | 0.13 |
CVD = Cardiovascular disease.
*P-values test the hypothesis that of no differences among the four WOMAC function quartiles and were obtained using ANOVA (continuous, normally distributed covariates), Wilcoxon rank sum tests (ordinal covariates), and chi-square tests (categorical covariates).