In patients with primary progressive multiple sclerosis, older age and bilateral motor symptoms at disease onset predicted faster disability progression in a retrospective analysis of prospectively collected data.
Age was the most important predictor, but both factors seemed to affect disability accumulation throughout the course of primary progressive multiple sclerosis (PPMS), in contrast to the distinct stages and risk factors that characterize relapsing-remitting disease, said Dr. Marcus W. Koch and his associates at the University of Calgary (Alta.).
Primary progressive disease affects about 10%-20% of MS patients. To study its natural history, the investigators analyzed data on 446 patients with PPMS who were followed for a median of 14 years from disease onset (J. Neurol. Neurosurg. Psychiatry 2014 Aug. 4 [doi:10.1136/jnnp-2014-307948]).
Patients reached Expanded Disability Status Scale (EDSS) scores of 4 and 6 a median of 5 and 9 years after disease onset, the researchers said. Median age at EDSS = 4 was 51 years, and median age at EDSS = 6 was 55 years, they added. For each 1-year increase in age at disease onset, time to progression to EDSS = 4 decreased by 3% (hazard ratio per 1-year increase, 1.03; 95% confidence interval, 1.02-1.04), and time from onset to EDSS = 6 decreased by 4% (HR, 1.04; 95% CI, 1.02-1.05), the researchers reported.
Patients with bilateral motor onset symptoms also progressed to EDSS scores of 4 and 6 significantly faster than did patients with unilateral onset motor symptoms (P = .005 and .03, respectively), the investigators reported.
The researchers excluded some patients from analyses because of missing data, and these patients were significantly more likely to be female and to have a younger age at onset than were the patients who were included in analyses. They also did not subgroup PPMS patients by disease course because the criteria for these subcategories were not published until after the study began, they said (Neurology 2014;83:278-86).
Funding information for the study was not available. The authors reported no conflicts of interest.