Study Protocol: The Norfolk Diabetes Prevention Study [NDPS]: a 46 month multi - centre, randomised, controlled parallel group trial of a lifestyle intervention [with or without additional support from lay lifestyle mentors with Type 2 diabetes] to prevent transition to Type 2 diabetes in high risk groups with non - diabetic hyperglycaemia, or impaired fasting glucose

Background: This 7 year NIHR programme [2011-2018] tests the primary hypothesis that the NDPS diet and physical activity intervention will reduce the risk of transition to type 2 diabetes (T2DM) in groups at high risk of Type 2 diabetes. The NDPS programme recognizes the need to reduce intervention costs through group delivery and the use of lay mentors with T2DM, the realities of normal primary care, and the complexity of the current glycaemic categorisation of T2DM risk. Methods: NDPS identifies people at highest risk of T2DM on the databases of 135 general practices in the East of England for further screeningwith ab fasting plasma glucose and glycosylated haemoglobin [HbA1c]. Thosewith an elevated fasting plasma glucose [impaired fasting glucose or IFG] with orwithout an elevated HbA1c [non -diabetic hyperglycaemia; NDH] are randomised into three treatment arms: a control arm receiving no trial intervention, an arm receiving an intensive bespoke group-based diet and physical activity intervention, and an arm receiving the same interventionwith enhanced support from people with T2DM trained as diabetes prevention mentors [DPM]. The primary end point is cumulative transition rates to T2DM between the two intervention groups, and between each intervention group and the control group at 46months. Participants with screen detected T2DM are randomized into an equivalent prospective controlled trialwith the same intervention and control arms with glycaemic control [HbA1c] at 46months as the primary end point. ParticipantswithNDH and a normal fasting plasma glucose are randomised intoanequivalent prospective controlled intervention trialwith follow up for 40months. The intervention comprises six education sessions for the first 12 weeks and then up to 15 maintenance sessions until intervention end, all delivered in groups, with additional support fromaDPM in one treatment arm. Discussion: TheNDPS programme reports in 2018 andwill provide trial outcome data for a group delivered diabetes prevention intervention, supported by lay mentors with T2DM, with intervention inmultiple at risk glycaemic categories, and that takes into account the realities of normal clinical practice.