Baseline characteristics of the cohort of workers’ compensation claimants with short-term disability claims for injuries to the low back from 1998 to 2009 and with at least one prescription opioid, NSAID or SMR dispense in the first 8 weeks after injury (n=55 571)
| Variable | All claimants n (%) | By exposure group at 8 weeks | ||
| NSAIDs and/or SMRs (n=29 104) | Opioids only (n=7730) | Opioids with NSAIDs and/or SMRs (n=18 737) | ||
| n (%) | n (%) | n (%) | ||
| Sex | ||||
| Women | 20 517 (36.9) | 11 313 (38.9) | 2801 (36.2) | 6403 (34.2) |
| Men | 35 054 (63.1) | 17 791 (61.1) | 4929 (63.8) | 12 334 (65.8) |
| Age at injury | ||||
| 18–24 | 4838 (8.7) | 2957 (10.2) | 610 (7.9) | 1271 (6.8) |
| 25–34 | 11 911 (21.4) | 6434 (22.1) | 1518 (19.6) | 3959 (21.1) |
| 35–44 | 17 871 (32.2) | 9223 (31.7) | 2449 (31.7) | 6199 (33.1) |
| 45–54 | 15 019 (27.0) | 7476 (25.7) | 2182 (28.2) | 5361 (28.6) |
| ≥55 | 5932 (10.7) | 3014 (10.4) | 971 (12.6) | 1947 (10.4) |
| Neighbourhood income quintile | ||||
| 1 (Lowest) | 12 658 (22.8) | 6528 (22.4) | 1835 (23.7) | 4295 (22.9) |
| 2 | 13 452 (24.2) | 7058 (24.3) | 1834 (23.7) | 4560 (24.3) |
| 3 | 11 992 (21.6) | 6273 (21.6) | 1669 (21.6) | 4050 (21.6) |
| 4 | 10 259 (18.5) | 5434 (18.7) | 1408 (18.2) | 3417 (18.2) |
| 5 (Highest) | 7210 (13.0) | 3811 (13.1) | 984 (12.7) | 2415 (12.9) |
| Regional health authority | ||||
| Interior | 8258 (14.9) | 3907 (13.4) | 1290 (16.7) | 3061 (16.3) |
| Fraser | 24 619 (44.3) | 13 515 (46.4) | 2917 (37.7) | 8187 (43.7) |
| Vancouver Coastal | 10 371 (18.7) | 5786 (19.9) | 1532 (19.8) | 3053 (16.3) |
| Vancouver Island | 9013 (16.2) | 4291 (14.7) | 1554 (20.1) | 3168 (16.9) |
| Northern | 3310 (6.0) | 1605 (5.5) | 437 (5.7) | 1268 (6.8) |
| Year of injury | ||||
| 1998/1999 | 9833 (17.7) | 5225 (18.0) | 1571 (20.3) | 3037 (16.2) |
| 2000/2001 | 9419 (17.0) | 5082 (17.5) | 1366 (17.7) | 2971 (15.9) |
| 2002/2003 | 8920 (16.1) | 4623 (15.9) | 1216 (15.7) | 3081 (16.4) |
| 2004/2005 | 9179 (16.5) | 4789 (16.5) | 1277 (16.5) | 3113 (16.6) |
| 2006/2007 | 9439 (17.0) | 4827 (16.6) | 1278 (16.5) | 3334 (17.8) |
| 2008/2009 | 8781 (15.8) | 4558 (15.7) | 1022 (13.2) | 3201 (17.1) |
| ICD-9 diagnosis on claim | ||||
| 722—Intervertebral disc disorders | 2353 (4.2) | 710 (2.4) | 350 (4.5) | 1293 (6.9) |
| 724—Other and unspecified disorders of back | 5117 (9.2) | 2581 (8.9) | 873 (11.3) | 1663 (8.9) |
| 846—Sprains and strains of sacroiliac region | 11 658 (21.0) | 6375 (21.9) | 1578 (20.4) | 3705 (19.8) |
| 847—Sprains and strains lumbar, sacrum, coccyx, unspecified site of back | 36 443 (65.6) | 19 438 (66.8) | 4929 (63.8) | 12 076 (64.5) |
| Occupation at time of injury involving heavy physical strength requirements (handle loads ˃20 kg) and/or working near/with equipment, instruments, machinery or power/hand tools that may be a source of accident or injury | ||||
| No | 23 602 (42.5) | 12 821 (44.1) | 3303 (42.7) | 7478 (39.9) |
| Yes | 31 969 (57.5) | 16 283 (55.9) | 4427 (57.3) | 11 259 (60.1) |
| Number of prior workers’ compensation claims in the 2 years before injury* | ||||
| 0 | 37 699 (67.8) | 19 969 (68.6) | 5167 (66.8) | 12 563 (67.0) |
| 1 | 12 406 (22.3) | 6428 (22.1) | 1770 (22.9) | 4208 (22.5) |
| ≥2 | 5466 (9.8) | 2707 (9.3) | 793 (10.3) | 1966 (10.5) |
| Cumulative days supplied with opioids in the year before injury | ||||
| 0 | 42 413 (76.3) | 24 389 (83.8) | 5188 (67.1) | 12 836 (68.5) |
| 1–14 | 8341 (15.0) | 3780 (13.0) | 1243 (16.1) | 3318 (17.7) |
| ≥15 | 4817 (8.7) | 935 (3.2) | 1299 (16.8) | 2583 (13.8) |
| Cumulative days supplied with NSAIDs in the year before injury | ||||
| 0 | 41 066 (73.9) | 21 804 (74.9) | 6016 (77.8) | 13 246 (70.7) |
| 1–14 | 5580 (10.0) | 2973 (10.2) | 697 (9.0) | 1910 (10.2) |
| ≥15 | 8925 (16.1) | 4327 (14.9) | 1017 (13.2) | 3581 (19.1) |
| Cumulative days supplied with SMRs in the year before injury | ||||
| 0 | 51 151 (92.1) | 27 170 (93.4) | 7175 (92.8) | 16 806 (89.7) |
| 1–14 | 2355 (4.2) | 1091 (3.7) | 283 (3.7) | 981 (5.2) |
| ≥15 | 2065 (3.7) | 843 (2.9) | 272 (3.5) | 950 (5.1) |
*Includes all types of claims (short-term disability, long-term disability, healthcare only, vocational rehabilitation) for any diagnosis (not limited to low back pain claims).
ICD-9, International Statistical Classification of Diseases and Related Health Problems, Ninth Revision; NSAID, non-steroidal anti-inflammatory drug; SMR, skeletal muscle relaxant.