Inpatient or outpatient occupational rehabilitation – what works best for whom? A non-randomized clinical trial

Purpose This study compared return to work (RTW) outcomes among Norwegian patients with musculoskeletal or common mental disorders participating in a 4-week inpatient or 3-month outpatient occupational rehabilitation program to examine how program type and pre-intervention sick-leave history influenced RTW. Methods An observational cohort design that included 857 participants, categorized into five subgroups by pre-intervention absence from work. The primary outcome was time to first month without sickness absence benefits. The secondary outcome was total time without benefits. Both outcomes were assessed at 6-, 12-, and 24-month follow-ups. Results The average duration on benefits pre-intervention was 6.3 months for outpatients and 10.8 months for inpatients. Pre-intervention work absence duration was the strongest predictor of RTW at both clinics. The effects of program type on RTW were time- and group-dependent. Outpatients returned to work earlier, but inpatients’ RTW rates caught up with or surpassed outpatients between 3 and 9 months after program initiation. At 10 months, outpatients again showed better RTW outcomes. Among individuals with 6 weeks through 5 months full-time benefits pre-intervention, inpatients had better RTW outcomes than outpatients. Conversely, among those on part-time benefits, outpatients had better RTW outcomes than inpatients. After adjusting for group-by-time and clinic-by-benefit interactions, inpatient participants generally had higher chances of stable RTW (> 4 weeks) at all follow-up points. Conclusion Pre-intervention duration of work absence strongly affected RTW. The effectiveness of inpatient versus outpatient rehabilitation varied by patient subgroup and time, highlighting the importance of tailoring rehabilitation to individual sick-leave histories. Trial registration: Current controlled trials https://doi.org/10.1186/ISRCTN12033424, 15.10.2014, retrospectively registered.