A total of 351 patients were randomized to brief (n
175) or multidisciplinary intervention (n
176). In the brief intervention group the mean age of the patients was 41.9 (SD
10.4) years and 50.3% were women. In the multidisciplinary intervention group the mean age of the patients was 42.1 (SD
10.5) years and 54.0% were women. Seven patients dropped out after randomization, but they were included in the analyses as outcome data were available for all patients. However, another seven patients had not answered the questions which were used to form the subgroups at baseline. Therefore, the numbers of patients were 227 and 117 in Subgroup 1 and 2, respectively.
The fractions of patients with RTW for at least four weeks during the two-year follow-up period were not statistically significantly different in the brief and multidisciplinary intervention groups (Table
). The estimated number of subjects who returned to work decreased linearly with an increase in the required duration of the period without sick leave. However, the relative chance of RTW associated with the two interventions was similar for different durations, and the chances of RTW were not statistically significantly different between the intervention groups (Table
). When a four-week duration without sick leave compensation was used to define RTW, 76% and 72% accomplished RTW during the first year in the brief and multidisciplinary intervention groups, respectively (Table
Impact of the duration of the period without benefits after sick leave on number of patients with return to work (RTW) in the first year based on survival analyses
The number of weeks on sick leave in the first year was statistically significantly lower in the brief intervention group (median 14 weeks) than in the multidisciplinary intervention group (median 20 weeks, Table
The RTW status registered in the 52nd week after the first visit were not statistically significantly different in the in the brief and multidisciplinary intervention group, 66% and 61% respectively. (Table
). Among those who were not healthy enough to return to normal work, most were on sick leave, but some had modified work and a few had become excluded from the labour market and were receiving early retirement or temporary social benefits (Table
). Sick leave status was observed for 93 participants in the 52nd week and 71% of these patients had uninterrupted sick leave since the first visit at the Spine Center, i.e. sick leave after 52 weeks was known to be due to LBP. This was only the case for 32% of 62 patients on sick leave at the 104th week.
The subgroup analyses showed a better effect for all three outcome measures in “Subgroup 1” by brief intervention as compared to the multidisciplinary intervention, but RTW status in the 52nd week was not statistically significantly different between the intervention groups (Table
). In “Subgroup 2”, the tendency was in the opposite direction, even if the differences fell short of reaching the level of statistical significance (Table
). “Survival curves” based on analyses over a two-year period showed that a few more patients had succeeded in RTW than during the first year (Table
) (HR 0.86; 95% CI: 0.68-1.09).
Return to work (RTW) and sick leave outcomes in the brief and multidisciplinary intervention groups within Subgroup 1 (those with influence on the planning of their own work and no perceived risk of losing job and/or being a work injury claimant)
Return to work (RTW) and sick leave outcomes in the brief and multidisciplinary intervention groups within Subgroup 2 (those without influence on the planning of their own work or feeling at risk of losing job and not a work injury claimant)
The RTW status registered in the 104th week after the first visit showed RTW percentages that were lower than those registered in the 52nd week; but like in the 52nd, the differences between the two intervention groups were not statistically significantly different (Table
). In both intervention groups, more patients had modified jobs or were excluded from the labour market at the two-year follow-up than at the one-year follow-up.
The number of weeks on sick leave was lower during the second year than during the first year and it did not statistically significantly differ between the two intervention groups (Table
). The survival analyses at the two-year follow-up showed a better effect in “Subgroup 1” by brief intervention as compared to the multidisciplinary intervention, but RTW status in the 104th week was not statistically significantly different (Table
). In “Subgroup 2”, the differences in RTW between interventions at the two-year follow-up were in the opposite direction to those of “Subgroup 1”, but they were not statistically significant (Table
Effect modification analyses based on Cox regression adjusted for gender and age where the patients were categorized with respect to “Subgroup 1” and “Subgroup 2” showed a statistically significant modification on the effect of brief and multidisciplinary intervention both at the one-year (p
0.006) and the two-year follow-up (p
0.017). In these analyses, RTW was defined as four consecutive weeks without benefits, and at both follow-up times, the brief intervention appeared more effective than the multidisciplinary intervention in “Subgroup 1”, and the opposite pattern was present in “Subgroup 2”.
For those who experienced RTW during the first year, recurrent sick leave was monitored during the second year of follow-up. New episodes of sick leave were experienced by 42% of the participants. Table
shows that the median number of sick leave weeks was 0 in the second year in both intervention groups, but 25% (75 percentile) experienced at least 7 and 11 weeks of sick leave in the brief and multidisciplinary intervention groups, respectively. The difference in the number of new episodes between the intervention groups was not statistically significant, and similar patterns were found in the subgroups. The mean numbers of new weeks with sick leave were 6.5 and 7.8 in the brief and the multidisciplinary intervention group, respectively.