Clinical and demographic predictors of cognitive performance in multiple sclerosis. Do diagnostic type, disease duration, and disability matter?

Patients with chronic progressive multiple sclerosis often perform more poorly on cognitive tasks than do patients with the relapsing-remitting form of this disease. Whether these differences reflect an independent influence of disease type on cognitive performance is uncertain. We used multiple regression techniques to determine how well performance on a number of tasks done poorly by groups of patients with multiple sclerosis could be predicted by disease type and its confounds: age, disease duration, and disability status as well as other demographic variables. Disease types were assigned longitudinally, based on serial neurological examinations at 6-month intervals over a minimum of 2 years. None of the demographic or clinical variables predicted cognitive performance with more than minimal accuracy. These findings fail to provide support for the assertion that disease type is an important independent determinant of cognitive impairment in multiple sclerosis.