Introduction
Type 2 diabetes is an important and growing global health concern1 2 which leads to serious complications and an elevated risk of other cardiovascular diseases.2 Prevention of diabetes is a major international public health objective.2 3 Risk factors for type 2 diabetes include genetics, age, ethnicity, and obesity.2 4 Among those with elevated blood glucose levels, around 5%–10% are expected to develop type 2 diabetes each year, with estimates varying by country and population studied.5 Effective ways to delay or prevent progression to type 2 diabetes include lifestyle changes such as losing weight, eating a healthier diet, and increasing physical activity.6–8 Diabetes prevention programs (DPPs) have been established in many parts of the world, offering support to achieve lifestyle change among people at risk of type 2 diabetes. Evidence from trials suggests they can lead to a reduced incidence of type 2 diabetes,9 10 and this has been confirmed, with smaller effect sizes, in translational studies in routine practice.11–14
Aziz et al12 noted that the public health impact of a DPP depends on participation as well as population coverage. Their international review of 38 real-world DPPs defined uptake as the proportion enrolled on a program of those invited, categorized as low (≤33%), moderate (34%–66%), or high (≥67%). They found wide variation in uptake and concluded that uptake had a considerable impact on lowering diabetes risk. Retention of participants in DPPs is less often reported, and definitions used to measure uptake, retention, and completion vary between studies. Variation in participation may reflect different recruitment strategies and method of enrollment, assorted retention or completion milestones, as well as diversity in intensity and duration. This prevents straightforward comparisons between interventions. Poor uptake and retention are likely to result in wasted resources. Analysis of variation in DPP participation across demographic groups has not been possible in earlier studies because large population samples are needed; such analyses could reveal the extent of any inequalities in access, allowing providers to target resources to areas or groups where participation is low.
The Healthier You: NHS DPP is a behavior change program in England offering education on healthy eating and lifestyle, and help to lose weight and increase physical exercise,15 designed based on international evidence and expert opinion.11 16 Between 2016 and 2019 the DPP was introduced across England in three waves, delivered by four private service providers.17 The National Health Service (NHS) in England is organized geographically into clinical commissioning groups (CCGs), and at a higher level into sustainability and transformation partnerships (STPs). In general, a single provider was commissioned by each STP, but local implementation of referrals from primary care was managed by CCGs.
The DPP targeted adults over 18 with non-diabetic hyperglycemia (NDH), defined by the National Institute for Health and Care Excellence as glycated hemoglobin (HbA1c) of 6.0%–6.4% (42–47 mmol/mol) or fasting plasma glucose (FPG) level of 5.5–6.9 mmol/L. Eligible patients were identified in primary care and referred to a local provider via one of two main routes. ‘Consultation route’ referrals were made by a primary care professional following a consultation with the patient. ‘Letter route’ referrals resulted after a letter was sent to eligible patients identified by a search of general practice records, informing them that they were at elevated risk of type 2 diabetes and advising them to contact their local provider to self-refer.
Participants were offered an individual initial assessment, followed by regular group education and exercise sessions, comprising at least 16 hours of contact over 9–12 months.
We aimed to investigate the extent of uptake, retention and completion in the NHS DPP and report on variation in service delivery and participation among patient subgroups and between different providers and sites.
The team involved in developing and implementing the DPP has already published results on program participation18 19 using the same data source. For the first time, variation in participation is reported by geographical site and service provider, by different methods of referral from primary care, and accounting for out-of-hours service delivery, all of which are important for understanding how variation in the delivery of a DPP intervention across a nation may impact on participation, after adjustment for variation in case mix.