The Diabetes Control and Complications Trial (DCCT) and its long-term follow-up, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, radically influenced the management of type 1 diabetes by showing the fundamental importance of strict glycaemic control in preventing diabetic complications.1 Cognitive function, which was assessed at baseline, has been followed up longitudinally, with no significant abnormalities being observed at 2 and 5 years and only minor abnormalities after 18 years.