Randomised controlled trials (RCTs) that compared statin plus interferon with interferon alone (the control) were eligible for inclusion if they were of patients with multiple sclerosis. At least one of the following outcomes had to be reported: the clinical relapse rate; disease progression; or the Expanded Disability Status Scale (EDSS) score.
In included trials, the mean patient age ranged from 29.3 to 45.1 years and the percentage of male patients ranged from 14.2 to 37.5. All of the trials were of patients with relapsing-remitting multiple sclerosis, and in all but one, patients were already being treated with interferon beta-1a, given once or three times per week. Across all trial groups, the weekly interferon dose ranged from 30 micrograms (μg) to 132μg; half of the trials were of intra-muscular administration and the other half were of subcutaneous administration. The statins were taken orally and were simvastatin or atorvastatin, with daily doses ranging from 20mg to 80mg. Treatment duration ranged from six to 24 months.
Two reviewers independently selected trials for inclusion; it was unclear how any discrepancies were resolved.