Effects of multidisciplinary inpatient rehabilitation for chronic back or neck pain: a register-linkage study of sickness absences and analgesic purchases in an occupational cohort.

OBJECTIVE To determine the effects of multidisciplinary in-patient rehabilitation for chronic back or neck pain on sickness absences and analgesic purchases. DESIGN A prospective observational study. SETTING 10 towns in Finland. PARTICIPANTS 34 838 local government employees, including 418 participants in rehabilitation for chronic back pain and 195 participants in rehabilitation for chronic neck pain between 1994 and 2002. MAIN OUTCOME MEASURES The annual rates of short (1-3 days), long (>3 days), and very long (>21 days) sickness absences and the defined daily doses (DDD) of prescribed analgesics. RESULTS The rate of very long (>21 days) sickness absence among the chronic back pain rehabilitees was 3.03-fold (95% CI 2.55 to 3.60) compared to the non-rehabilitees in the year before rehabilitation. This ratio declined to 1.88 (95% CI 1.65 to 2.37) three years after rehabilitation. No further decline in the rate of very long sickness absence was observed in the subsequent years. For chronic neck pain rehabilitees, no evidence of the effectiveness of rehabilitation on sickness absence was found. In relation to consumption of analgesics, the mean rate of DDDs declined among the back and neck pain rehabilitees after rehabilitation compared to the non-rehabilitees. CONCLUSIONS Multidisciplinary in-patient rehabilitation for chronic back pain may decrease the risk of very long sickness absence for three years. In relation to rehabilitation for chronic neck pain, no changes in sickness absences were found.