Introduction 1 2 6 7 8 9 10 7 10 10 15 11 12 14 16 15 The purpose of this study was to describe the health status, assessed by multiple outcome measures, and work limitations, in injured workers with MSK disorders 1 month post-injury stratified by RTW status, and to document their RTW trajectories over a period of 6 months post-injury. Materials and methods Study design The present study was conducted within the sampling frame of a prospective study of Ontario workers with a back or upper extremity (UE) MSK disorder, who filed a Workplace Safety and Insurance Board (WSIB) lost-time injury claim. Data was collected from two sources: self-reports of participants and WSIB administrative data. The participants were interviewed by phone at baseline (1 month post-injury), and 6 months post-injury. Participants provided information on their RTW experience, workplace, healthcare provider, insurer, and physical and mental health. From the WSIB, administrative information on sociodemographics, workplaces, and claims (e.g., site of injury, claim status, time receiving wage replacement benefits) was obtained. This information was linked to the interview data, when the participants provided written consent for linkage. Ethical approval for the study was granted by the University of Toronto’s Ethics Review Board. Participants were given the option to withdraw from the study at any point and to decline data linkage of their questionnaire responses with their WSIB data. It was made explicit to the respondents that study participation would in no way affect their claim with the insurer. Participant recruitment and final study sample 1 Fig. 1 Recruitment procedure and flow of participants  SD n Definition of the RTW status RTW-S RTW-R working RTW-R not working No RTW RTW-R Measurements: health outcomes and work limitations Pain intensity 17 18 present time past month Functional status 19 20 25 26 27 26 z z z z General health 28 29 29 28 30 Depressive symptoms 31 past week 31 Work limitations 32 35 Sociodemographics, days off work, and comorbidity Participants provided information on age, gender, education, living status, number of children under the age of 18, and personal income. Information on occupational status was obtained from the WSIB database. One self-reported question assessed how many full days of work a participant had missed due to the injury. In addition, data on time receiving wage replacement benefits was obtained from the WSIB database. The Saskatchewan Comorbidity Scale was used to measure comorbidity (Jaroszynski et al., unpublished work). The 16/14-item (women/men) self-report scale assesses the presence and severity of health problems. Participants are instructed to indicate whether they currently have a particular health problem/disease and, if so how much it has affected their health in the last 6 months. The response options range from 1 = “not at all” to 4 = “severe.” In the present study, two additional items pertaining to gynecological problems and pregnancy status were added for women. Responses were combined and categorized as: no comorbidity, comorbidity with no/mild effect on health, and comorbidity with moderate/severe effect on health. Statistical analyses 2 36 Results Baseline characteristics and selection bias analysis 1 SD SD Table 1 n a  Total RTW-S RTW-R No RTW N N N N Gender N (%) N (%) N (%) N (%)     Female 282 (44.6) 123 (42.0) 48 (54.5) 110  (45.1)     Male 350 (55.4) 170 (58.0) 40 (45.5) 134 (54.9) Age categories     15–29 years 93 (14.7) 45 (15.4) 9 (10.2) 35 (14.4)     30–39 years 137 (21.7) 58 (19.8) 29 (33.0) 48 (19.8)     40–49 years 228 (36.1) 109 (37.2) 31 (35.2) 87 (35.8)     ≥50 years 173 (27.4) 81 (27.6) 19 (21.6) 73 (30.0) Living with/without partner     Living with partner 433 (68.5) 221 (75.4) 54 (61.4) 156 (63.9)     Not living with partner 199 (31.5) 72 (24.6) 34 (38.6) 88 (36.1) Children under age 18     No children  341 (54.0) 158 (53.9) 48 (54.5) 131 (53.7)     1 child 118 (18.7) 53 (18.1) 17 (19.3) 47 (19.3)     2 children 118 (18.7) 57 (19.5) 15 (17.0) 44 (18.0)     ≥3 children  55 (8.7) 25 (8.5) 8 (9.1) 22 (9.0) Education     Some high school 112 (17.7) 46 (15.7) 16 (18.2) 49 (20.1)     High school completed 177 (28.0) 75 (25.6) 30 (34.1) 69 (28.3)     Some university or college 130 (20.6) 70 (23.9) 14 (15.9) 45 (18.4)     University/college completed 213 (33.7) 102 (34.8) 28 (31.8) 81 (33.2) N b     White collar 89 (18.6) 47  (20.9) 13 (17.6) 29 (16.4)     Pink collar 156 (32.6) 71 (31.6) 26 (35.1) 58 (32.8)     Blue collar-indoor 99 (20.7) 54 (24.0) 15 (20.3) 30 (16.9)     Blue collar-outdoor 68 (14.2) 28 (12.4) 10 (13.5) 28 (15.8)     Missing 67 (14.0) 25 (11.1) 10 (13.5) 32 (18.1) Personal income     <$20,000 95 (15.0) 31 (10.6) 12 (13.6) 47 (19.3)     $20,000–39,999 240 (38.0) 111 (37.9) 32 (36.4) 96 (39.3)     $40,000–59,999 180 (28.5) 88 (30.0) 28 (31.8) 64 (26.2)     >$60,000 81 (12.8) 46 (15.7) 9 (10.2) 25 (10.2)     Missing 36 (5.7) 17 (5.8) 7 (8.0) 12 (4.9) n     ≤37.5 179 (28.3) 84 (28.7) 24 (27.3) 69 (28.3)     >37.5–40.0 281 (44.5) 128 (43.7) 40 (45.5) 110 (45.1)     >40.0 172 (27.2) 81 (27.6) 24 (27.3) 65 (26.6) c    n n n SD 19.1 (8.9) 14.2 (7.1) 18.7 (8.4) 25.9 (6.5)     Days; median 20.0  13.0  19.0  29.0  Self-reported full days off work due to injury SD 14.5 (7.1) 10.5 (5.1) 14.1 (6.9) 19.7 (6.1)     Days; median 14.0  10.0  13.5  19  n     Back 418 (66.1) 214 (73.0) 64 (72.7) 134 (54.9)     Upper extremities 214 (33.9) 79 (27.0) 24 (27.3) 110 (45.1) n     No 513 (81.2) 238 (81.2) 72 (81.8) 197 (80.7)     Yes, with no/mild effect on health 33 (5.2) 16 (5.5) 5 (5.7) 12 (4.9)     Yes, with moderate/severe effect on health 86 (13.6) 39 (13.3) 11 (12.5) 35 (14.4) a  N N b  c  N N N n n 1 2 n Table 2 Comparison of baseline study participants with algorithm-selected potential study participants Variable n n n     Female 282 (44.6) 1,365 (36.8     Male 350 (55.4) 2,347 (63.2) SD 42.2 (10.8) (43) 40.3 (11.3) (40.7) n     Females: 15–29 years 40 (6.3) 262 (7.1)     Females: 30–39 years 59 (9.3) 348 (9.4)     Females: 40–49 years 109 (17.2) 428 (11.5)     Females: ≥50 years 74 (11.7) 327 (8.8)     Males: 15–29 years 53 (8.4) 524 (14.1)     Males: 30–39 years 78 (12.3) 630 (17.0)     Males: 40–49 years 119 (18.8) 714 (19.2)     Males: ≥50 years 99 (15.7) 479 (12.9) n     <20 employees 58 (9.2) 335 (9.0)     20–99 employees 100 (15.8) 680 (18.3)     100–999 employees 190(30.1) 1,166 (31.4)     ≥1,000 employees 150 (23.7) 769 (20.7)     Schedule 2 134 (21.2) 761 (20.5) n     Automotive, manufacturing, steel 109 (17.2) 875 (23.6)     Service 127 (20.1) 812 (21.9) a 146 (23.1) 817 (22.0)     Healthcare 85 (13.4) 425 (11.4)     Transportation 55 (8.7) 333 (9.0)     Chemical/processing, electrical, food 31 (4.9) 212 (5.7)     Construction 14 (2.2) 154 (4.1)     Agriculture, forest, pulp and paper, mining 15 (2.4) 83 (2.2)     Unknown 50 (7.9) 1 (0.0) n b     White collar 109 (18.7) 624 (16.8)     Pink collar 209 (35.9) 1,112 (30.0)     Blue collar-indoor 132 (22.7) 1,026 (27.6)     Blue collar-outdoor 86 (14.8) 631 (17.0)     Missing 45 (7.7) 319 (8.6) n     ≤$447.68 116 (18.4) 819 (22.1)     $447.68–≤$880.00 281 (44.5) 1,890 (50.9)     ≥$880.00 157 (24.8) 978 (26.3)     Missing 78 (12.3) 25 (0.7) SD c 20.6 (9.0) (25) 15.9 (9.4) (13) SD d 58.7 (57.2) (33) 37.6 (50.2) (14) n c     No 507 (90.7) 3,481 (93.8)     Yes 52 (9.3) 231 (6.2) n d     No 463 (82.5) 3,286 (88.5)     Yes 98 (17.5) 426 (11.5) n     Lost-time-accepted 431 (68.2) 2,893 (77.9)     Lost-time-pending 171 (27.1) 765 (20.6)     Lost-time-denied 19 (3.0) 43 (1.2)     Lost-time-amalgamated 5 (0.8) 1 (0.0)     No lost-time-accepted 6 (0.9) 6 (0.2) a  b  n c n d n Note: Group differences in baseline characteristics A total of 625 participants were categorized into one of the four RTW status groups. The remaining seven participants were working when interviewed at baseline, but not asked about recurrence(s) due to an error in a skip pattern of the questionnaire, which was subsequently corrected. At baseline (approximately 1 month post-injury), 47% of the participants reported a sustained first return to work, 5% a return to work with recurrence(s) of work absence and working at time of interview, almost 9% a return to work with recurrence(s) of work absence and not working at time of interview, and 39% no return to work. 2 p 2  p F p F p 2  p Group differences in health outcomes and work limitations 3 Table 3 N  a RTW-R No RTW N N N Estimated mean (95% CI) Estimated mean (95% CI) p Estimated mean (95% CI) p Perceived pain Range 0–10     Pain at time of interview 3.84 (3.54–4.13) 5.19 (4.64–5.73) .000 5.94 (5.62–6.27) .000     Pain in the past month 8.45 (8.25–9.13) 8.78 (8.40–9.16) .421 8.90 (8.68–9.13) .014 Roland Morris N 52.73 (49.29–56.17) 68.14 (61.75–74.54) .000 75.66 (71.30–80.03) .000 Quick DASH N 47.58 (42.61–52.55) 54.94 (46.01–63.87) .469 63.15 (58.98–67.33) .000 Physical SF-12     Range 0–100 37.03 (35.98–38.09) 32.75 (30.80–34.69)  .000 31.63 (30.47–32.78) .000 Mental SF-12     Range 0–100 48.55 (47.18–49.91) 44.40 (41.88–46.92) .014 45.58 (44.08–47.07) .013 Depressive symptoms     CES-D; Range 0–60 13.16 (11.74–14.59) 18.15 (15.53–20.78) .003 18.70 (17.14–20.26) .000 Work limitations Range 0–100     Physical demands 46.00 (42.79–49.22) 62.81 (56.80–68.82)  .000 n.a.      Mental demands 17.12 (14.70–19.55) 29.41 (24.88–33.95) .000 n.a.      Output demands 18.65 (15.95–21.35) 35.59 (30.56–40.61) .000 n.a.      Time management 41.83 (38.43–45.23) 61.90 (55.61–68.20) .000 n.a.  a  Attrition analysis n n n n n RTW trajectories from baseline to 6 month follow-up 2 n n n Fig. 2 n a b c d  Discussion The findings of this cohort study suggest the presence of a pattern in baseline health states and work limitations specific to RTW status, 1 month post-injury. Workers with a sustained first return to work reported less pain, less functional disability, better physical and mental health, fewer depressive symptoms, and fewer work limitations compared to those who experienced a recurrence of work absence or who never returned to work. The study adds to the literature by demonstrating that depressive symptoms and limitations at work are prevalent in workers 1 month post-injury, including in those with a sustained first return to work. A substantial rate of recurrences of work absence over 6 months was found (38%), even in workers who had initially made a sustained first return to work at baseline (27%). Moreover, of those workers who did not return to work at baseline, 17% attempted to return and experienced a recurrence within 6 months of the injury, and 24% were still off work at 6 months post-injury. 11 12 14 15 14 29 37 38 When interpreting the results, the following methodological issues must be considered. Though reasonable for a study among claimants, the overall participation rate of 61% raises the question of selective participation, which may have biased the results. However, the cohort was shown to be representative of the most comparable claimant group with regards to basic demographic and workplace variables, but not with regards to duration of time receiving wage replacement benefits and rates of wage replacement re-instatement, suggesting the presence of more severe disability in the cohort. Hence, the generalizability of the results remains limited with respect to workers with less severe work disability. More importantly, the rates of self-reported recurrence of work absence may be inflated in our cohort. A related issue concerns the loss-to-follow-up of 29%. The attrition analysis demonstrated that non-respondents and respondents were similar with regards to time receiving wage replacement benefits, the occurrence of re-instatement of wage replacement benefits, and self-reported work absence duration. Non-respondents were younger males, worked longer hours, and were more likely to specify “back” as their primary pain site compared to respondents. 39 To conclude, the results of this prospective study suggest that workers who had a sustained first return to work report a better health status and fewer work limitations than those who experienced a recurrence after a first return to work or who did not return to work. However, it is also demonstrated that a return to work is not equivalent to a complete recovery from MSK disorders. Workers who had a sustained first return to work still reported meaningful health limitations, as compared to the general population and significant work limitations. Given the considerable impact of disability on worker health and costs for the workers, employers, and society, the findings highlight the importance of considering multiple health outcomes, including depressive symptoms and work limitations, when studying the complex process of return to work and when developing RTW interventions and disability management strategies.