Effect of age on outcomes of tertiary rehabilitation for chronic disabling spinal disorders

A prospective cohort study evaluating age as a factor in treatment outcomes for chronic disabling work-related spinal disorders undergoing tertiary rehabilitation.

To assess the association between age and objective psychosocioeconomic treatment outcomes for work-related spinal disorders undergoing functional restoration.

As early as the 1950s, a link between age and low back symptoms has been identified in the literature. Several studies have demonstrated that the occurrence of low back pain is positively correlated with age up to about 50-60 years, after which prevalence declines. It has been argued that this pattern is stronger for more severe, chronic back pain cases. Little research attention has been given to age as a factor in treatment outcomes for work-related spinal disorders.

A cohort of 1052 chronically disabled (none working full-time when starting the rehabilitation program) spinal disorder (CDSD) patients were placed into five groups based on age: Group 1, <25 years (22 +/- 2 years, n = 59); Group 2, 25-34 years (30 +/- 3 years, n = 301); Group 3, 35-44 years (39 +/- 3 years, n = 381); Group 4, 45-54 (49 +/- 3 years, n = 237); and Group 5, > or =55 years (59 +/- 4 years, n = 74). All patients completed a functional restoration program combining quantitatively directed exercise progression with a multimodal disability management approach using psychological and case management techniques. Before the start of the program, and again on completion of the program, all patients received a psychosocial evaluation and were also assessed on a variety of physical motion, strength, aerobic, and functional factors, and a cumulative score was calculated, which aggregates and averages these physical measures. A structured clinical interview examining socioeconomic outcomes (work return, health utilization, recurrent injury, and resolution of financial disputes) was conducted at 1 year after program completion, and at least partial information was obtained from this interview on all consecutive patients in the study.

The length of pretreatment disability increased with age (P < 0.001), as well as pretreatment surgery rates (P < 0.002). A Mantel-Haenzel chi2 test for linear trend across age groups revealed that the percentage of patients who returned to work declined progressively from 100% in Group 1 to 69% in Group 5 (P < 0.001). The same linear trend was revealed for the percentage of patients retaining work at the end of 1 year (98-62%, P < 0.001). Older workers returned to the same job and/or the same employer (P < 0.005). Younger workers found different jobs with new employers (48-11%, P < 0.0001). Analysis of variance for the disability questionnaire revealed that after treatment subjective disability progressively increased (while improvements decreased) from Group 1 to Group 5 (P < 0.01). The cumulative physical score variable, even normalized for age, was progressively lower from Group 1 to Group 5, both at pretreatment (P < 0.03) and post-treatment (P < 0.02).

The present study represents the first large-scale examination of the association between age and treatment outcomes for a work-related CDSD population. Age is significantly and linearly related to pretreatment duration of disability and frequency of pretreatment surgeries. After rehabilitation treatment there is a linear decrement in both work return and work retention, so that younger patients are far more likely to return and hold work after functional restoration. Older workers who go back to work are much more likely to return to the same employer and do the same job, or to become self-employed. Calculation of odds ratios revealed that patients >55 years are 5.68 times more likely to return to the same job and employer, relative to those <25 years; those >55 years were also approximately three times more likely than those <25 years to return to the same employer, compared with those <25 years. Younger workers are far more likely to take a different job and/or seek a new employer. Older patients are also somewhat more likely to seek a new health provider to deal with perceived residual pain/disability. This trend coincides with their higher post-treatment subjective disability levels, and their lower cumulative physical scores both prerehabilitation and postrehabilitation. However, age does not affect additional surgery rates, subsequent injuries, or delays in settling financial disputes.