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Original Investigation
November 2, 2020

Lifestyle Intervention With or Without Lay Volunteers to Prevent Type 2 Diabetes in People With Impaired Fasting Glucose and/or Nondiabetic Hyperglycemia: A Randomized Clinical Trial

Author Affiliations
  • 1Elsie Bertram Diabetes Centre, Department of Diabetes and Endocrinology, Norfolk and Norwich University Hospital National Health Service Trust, Norwich, England
  • 2Norwich Medical School, University of East Anglia, Norwich, England
  • 3School of Sport, Exercise & Rehabilitation Sciences, University of Birmingham, Birmingham, England
  • 4University of Exeter Medical School, College of Medicine & Health, University of Exeter, Exeter, England
  • 5Department of Diabetes and Endocrinology, Ipswich General Hospital, Ipswich, England
  • 6Department Clinical Biochemistry, Norfolk and Norwich University Hospital NHS Trust, Norwich, England
JAMA Intern Med. 2021;181(2):168-178. doi:10.1001/jamainternmed.2020.5938
Key Points

Question  Does a group-based lifestyle intervention (with or without trained volunteers with type 2 diabetes) reduce the risk of type 2 diabetes in people with current high-risk intermediate glycemic categories of impaired fasting glucose or nondiabetic hyperglycemia?

Finding  In this randomized clinical trial of 1028 participants with high-risk intermediate glycemic categories, the intervention significantly reduced the 2-year risk of type 2 diabetes by 40% to 47%, although lay volunteer support did not reduce the risk further. For every 11 participants treated, 1 diabetes diagnosis was prevented.

Meaning  Nearly half of the adult population has diabetes or a high-risk glycemic category, and this low-cost group-delivered intervention significantly reduced the risk of diabetes.


Importance  Nearly half of the older adult population has diabetes or a high-risk intermediate glycemic category, but we still lack trial evidence for effective type 2 diabetes prevention interventions in most of the current high-risk glycemic categories.

Objective  To determine whether a group-based lifestyle intervention (with or without trained volunteers with type 2 diabetes) reduced the risk of progression to type 2 diabetes in populations with a high-risk glycemic category.

Design, Setting, and Participants  The Norfolk Diabetes Prevention Study was a parallel, 3-arm, group-based, randomized clinical trial conducted with up to 46 months of follow-up from August 2011 to January 2019 at 135 primary care practices and 8 intervention sites in the East of England. We identified 141 973 people at increased risk of type 2 diabetes, screened 12 778 (9.0%), and randomized those with a high-risk glycemic category, which was either an elevated fasting plasma glucose level alone (≥110 and <126 mg/dL [to convert to millimoles per liter, multiply by 0.0555]) or an elevated glycated hemoglobin level (≥6.0% to <6.5%; nondiabetic hyperglycemia) with an elevated fasting plasma glucose level (≥100 to <110 mg/dL).

Interventions  A control arm receiving usual care (CON), a theory-based lifestyle intervention arm of 6 core and up to 15 maintenance sessions (INT), or the same intervention with support from diabetes prevention mentors, trained volunteers with type 2 diabetes (INT-DPM).

Main Outcomes and Measures  Type 2 diabetes incidence between arms

Results  In this study, 1028 participants were randomized (INT, 424 [41.2%] [166 women (39.2%)]; INT-DPM, 426 [41.4%] [147 women (34.5%)]; CON, 178 [17.3%] [70 women (%39.3)]) between January 1, 2011, and February 24, 2017. The mean (SD) age was 65.3 (10.0) years, mean (SD) body mass index 31.2 (5) (calculated as weight in kilograms divided by height in meters squared), and mean (SD) follow-up 24.7 (13.4) months. A total of 156 participants progressed to type 2 diabetes, which comprised 39 of 171 receiving CON (22.8%), 55 of 403 receiving INT (13.7%), and 62 of 414 receiving INT-DPM (15.0%). There was no significant difference between the intervention arms in the primary outcome (odds ratio [OR], 1.14; 95% CI, 0.77-1.7; P = .51), but each intervention arm had significantly lower odds of type 2 diabetes (INT: OR, 0.54; 95% CI, 0.34-0.85; P = .01; INT-DPM: OR, 0.61; 95% CI, 0.39-0.96; P = .033; combined: OR, 0.57; 95% CI, 0.38-0.87; P = .01). The effect size was similar in all glycemic, age, and social deprivation groups, and intervention costs per participant were low at $153 (£122).

Conclusions and Relevance  The Norfolk Diabetes Prevention lifestyle intervention reduced the risk of type 2 diabetes in current high-risk glycemic categories. Enhancing the intervention with DPM did not further reduce diabetes risk. These translatable results are relevant for current diabetes prevention efforts.

Trial Registration  ISRCTN Registry Identifier: ISRCTN34805606

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    1 Comment for this article
    “Lifestyle Intervention With or Without Lay Volunteers to Prevent Type 2 Diabetes in People With Impaired Fasting Glucose and/or Nondiabetic
    Michael Bergman, MD | NYU Grossman School of Medicine
    As HbA1c is insensitive for detecting prediabetes and diabetes, relying exclusively on this measurement may underestimate the incidence of dysglycemia. Those with NDH may have included individuals with IGT or T2D had an OGTT been performed. Therefore, it would be worthwhile comparing treatment response in people with IFG, NDH and the overall group. If the NDH group demonstrates greater responsiveness to lifestyle intervention than those with IFG, this would suggest that the HbA1c group likely has higher-risk subjects with IGT or T2D. Also, in the absence of an OGTT, “isolated IFG” is used incorrectly since this is defined as IFG without IGT. Thus far, of the prediabetes categories, the prevention of progression to T2D by lifestyle intervention has been proven only in IGT. Additional data is therefore required before it can be concluded that lifestyle intervention has a specific benefit in those with IFG alone.

    Michael Bergman, MD, FACP
    NYU Grossman School of Medicine
    Clinical Professor of Medicine and Population Health

    Jaakko Tuomilehto, MD, MA (sociol), PhD, FRCP (Edin), FESC
    Professor Emeritus of Public Health
    University of Helsinki, Helsinki, Finland