The Diabetes Control and Complications Trial (DCCT) ran from 1983-1993 and tested the value of intensified versus conventional control in 1441 patient volunteers with type 1 diabetes aged 13-39 years. They had a diabetes duration >1 year but <15 years, and had either no retinopathy (primary prevention group) or early retinopathy (secondary prevention group). The patients on intensified treatment group aimed to achieve an HbA1c ~6.0% by any treatment strategy (usually multiple injections or CSII). The study demonstrated a dramatic benefit of intensified glucose control in primary prevention of retinopathy, kidney disease or neuropathy; secondary prevention was associated with additional factors such as control of blood pressure and lipids. No cardiovascular benefit had emerged by the end of the trial in 1993, but long term follow-up showed that the risk of heart disease was 42% lower in participants in the intensified arm by 2005.