The prevalence of cognitive impairment in a community survey of multiple sclerosis.

A one in two alternate sample (N = 200) from a population-based register of 411 people with multiple sclerosis (MS) was studied. Out of this sample, 147 people with MS and 34 people with rheumatoid arthritis were interviewed at home and completed a battery of neuropsychological tests. Cognitive impairment was found in 46 per cent of those with MS, with memory impairment in 34 per cent and failure on tests of frontal lobe function in 33 per cent. Physical disability was associated with cognitive impairment. Memory impairment was more common in those who had had MS for 10 years or more. A significant minority of people with mild physical disability and some who had had MS for less than a decade nevertheless had cognitive impairment. Relationships between cognitive impairment, other disease variables and psychosocial factors were examined. Counselling and rehabilitation programmes for people with MS and their families should take account of cognitive deficits that may be present.