Objective: To assess whether the level of multiple sclerosis (MS) -related disability in the Olmsted County population has changed over a decade, and to evaluate how the rate of initial progression to moderate disability impacts further disability.
Methods: The Minimal Record of Disability (MRD) measured impairment, disability, and handicap for the 2000 (n = 201) prevalence cohort. The authors compared these results with the 1991 (n = 162) cohort; 115 patients were in both cohorts. The authors assessed retrospectively intervals at which Expanded Disability Status Scale (EDSS) scores of 3 (moderate disability), 6 (cane), and 8 (wheelchair) were reached.
Results: The distribution of the 2000 EDSS and MRD scores were not significantly different from the 1991 distribution. The median time from MS diagnosis, for the entire cohort, to EDSS scores of 3 and 6 was 17 and 24 years, respectively. At 20 years after onset, only 25% of those with relapsing-remitting MS had EDSS scores > or =3. The median time from diagnosis to EDSS score of 6 for the secondary and primary progressive groups was 10 and 3 years, respectively. Rate of progression from onset or diagnosis to EDSS score of 3 did not affect the rate of further disease progression. However, once an EDSS score of 3 was reached, progression of disability was more likely, and rate of progression increased.
Conclusions: The distribution of multiple sclerosis disability in the Olmsted community has remained stable for 10 years. Progression of disability for patients with relapsing-remitting multiple sclerosis or secondary progressive multiple sclerosis may be more favorable than reported previously. Once a clinical threshold of disability is reached, rate of progression increased.