Armitage led the 1999 Medical Research Council and British Heart Foundation Heart Protection Study, which included 20,000 participants.[6] The study is the largest that investigates the use of statins to prevent cardiovascular disease.[6] She was also the lead for the Study of the Effectiveness of Additional Reductions in Cholesterol and Homocysteine (SEARCH) study and the Heart Protection Study 2 (HPS2) Treatment of HDL to Reduce the Incidence of Vascular Events (THRIVE) study.[6][7] She demonstrated that statins are also safe for patients suffering from rheumatoid arthritis.[8]