The impact of age and comorbidity on the progression of disability in late-onset sequelae of poliomyelitis

Objectives: To describe the functional course over 5 years in patients aged 45 to 85 years with late-onset sequelae of poliomyelitis (LOSP) and to explore the impact of age and comorbidity.

Design: Prospective cohort study with 5 measurements over 5 years.

Setting: University hospital.

Participants: Subjects with LOSP (N=168).

Interventions: Not applicable.

Main outcome measures: FIM, Medical Outcomes Study 36-Item Short Form health survey for physical functioning subscale (SF-36-PF), walking test, isokinetic quadriceps strength, and cumulative illness rating scale (CIRS) for comorbidity.

Results: The FIM score (mean baseline +/- SD, 121+/-4) and SF-36-PF (mean baseline +/- SD, 39.5+/-24) decreased 2.2 and 3.7 points, respectively, over 5 years independent of age. The distance walked in 2 minutes (mean baseline +/- SD, 126.2+/-34m) decreased 4.5m, quadriceps strength (mean baseline +/- SD, 88.0+/-42.2Nm) declined 7Nm (8%), and CIRS (median baseline=6; range, 0-21) increased 1.5 points. A higher CIRS score was correlated with a lower FIM score and faster decrease in the FIM. A longitudinal model of factors associated with the FIM included sex, age, leg strength sum-score, arm strength sum-score, and CIRS score. The interaction of CIRS and leg strength sum-score with follow-up time was significant. A model of factors associated with SF-36-PF included sex, age, leg strength sum-score, and CIRS score.

Conclusions: Despite a reduction in muscle strength, disability increased little in patients with LOSP. Increased age and comorbidity has a negative effect on disability. Comorbidity and the severity of leg paresis affected the course of functional independence but not the course of perceived physical functioning.