Discussion
Using an NHS GP referral pathway into a 1 year DPP delivered by this commercial weight management provider achieved statistically significant reductions in measures of T2D risk.
The WWDPP achieved a significant reduction in HbA1c of 2.84 mmol/mol at 12 months (from 43.42±1.28 to 40.58±3.41, p<0.01). The results of this study match optimal interventions and represent clinical success according to the findings of PHE’s meta-analysis which found interventions that halt the upward trajectory of blood glucose but show no overall change could represent considerable clinical success, while, optimal interventions show a reduction in HbA1c of 2 mmol/mol or a reduction in FPG of 0.2 mmol/L or more.10 Although this study evidenced a 0.2 mmol/L reduction in FPG at 12 months, it was not statistically significant. However, given the potential issues with validity and reliability of measuring FPG, the significant HbA1c reduction may be considered a more reliable measure of success.23 It is acknowledged that not all patients at high risk go onto develop T2D; it is predicted that 5%–10% of people per year with NDH will progress to diabetes, with the same proportion converting back to normoglycemia.24 In this study, four patients (3%) developed T2D by 12 months.
The WWDPP achieved a significant mean reduction in weight of 10 kg and a mean reduction in BMI of 3.2 kg/m2. PHE’s meta-analysis found that compared with usual care the pooled mean weight loss of optimal interventions resulted in a mean weight loss of 2.46 kg.10 There was a statistically significant mean reduction in self-reported WC at 12 months; abdominal adiposity is argued to be a stronger predictor of T2D than BMI.25 PA is important especially for NDH patients as PA produces positive secondary outcomes such as improving beta cell function, insulin sensitivity and preventing CVD and depression.3 However, it is difficult for a non-exerciser to understand and define frequency and intensity of PA. Often when patients start exercising, they start to understand the definition of ‘moderate’ intensity and this could explain the large SD in activity reported.20 There were overall improvements in CVD risk,26 with significant reductions in BP (p<0.01), triglycerides (p<0.01) and cholesterol/HDL ratio (p<0.05) and a significant increase in HDL cholesterol in males (p<0.05) at 12 months.
The main strength of this study was that it was successful in addressing the complexities of implementing prevention programs in the real world; patients attended the program and achieved clinically significant results using ITT analysis. Of the eligible referrals, 77% attended the activation session (figure 1), while the PHE’s meta-analysis found that 37% of people who are eligible and referred will take up an intervention.10 The meta-analysis stated that adherence levels of 16 hours across 13 sessions over a 9-month period is optimal for diabetes risk reduction.10 The average compliance in this study was attendance at 29 out of 48 sessions, attended across an average of 40 weeks, as opposed to only 13 sessions across 9 months. However, there was an overall decline in attendance towards 12 months, and consequently the improvements in blood glucose and weight were not as rapid from 6 to 12 months. Therefore, long-term follow-up is needed to see if the results achieved in this 12-month study would be realized in the longer term. Flexibility of the program was important; most international DPPs are curriculum based and use a sequential curriculum in which each session is only offered once, if the session is missed it is difficult to make it up. In the WWDPP, these specifically designed sessions are theme lead, based on participant involvement and often repeated. Sessions are hosted at a variety of times and widely available locations, alongside the digital offerings. The program does not rely on reaching a critical mass to start and patients can attend any session of their choice.
A weakness of real world studies is that selection bias is inherent in uncontrolled, non-randomized and unblinded studies. In this study, there were low referral numbers, and therefore participation by; males, Black or minority ethnic (BME) groups and lower socioeconomic status populations. A higher proportion of the patients were women (75%), from white backgrounds (90%), with only 5% living in the most deprived quintile in the UK. It is likely that some of these features were because only a third of practices in the borough chose to participate in the study, and these were located in areas of lower deprivation and lower proportions of ethnic minorities. Due to ethical considerations, the study did not have a control group; without having a control group, it is difficult to assess if the significant impact on reducing diabetes risk was due to the WWDPP intensive lifestyle intervention or other variables the patient may have been exposed to. Therefore, consideration is needed when interpreting these findings to other populations. This study suffered from missing or inaccurate data; 32 patients’ (27%) weight measures and 27 patients’ (23%) blood glucose measures were lost to follow-up at 12 months, of which 10 patients had no comparable baseline, for example, referred patient based on FPG, followed up patient using HbA1c measurement. GPs also referred 32 (21%) unmotivated patients who did not engage in the program and 17 (10%) ineligible patients who did not match the inclusion criteria.
The Department of Health’s NHS Five Year Forward View strategy (2014) states that the UK will become the first country to implement at scale a national evidence-based DPP.27 The evidence for reducing T2D has been well established for a number of years using gold standard methodology such as RCTs, control groups with large sample sizes.2 This study evidences how to roll out prevention programs in the real world utilizing existing referral pathways. There is a need to spread the findings of what works to ensure the successful delivery of the Five Year Forward View, at a time when public sector budgets are being increasingly squeezed. A strength of this study was that it utilized an existing GP referral pathway rather than expensive outreach recruitment teams or costly letters to patients. There are advantages to utilizing a UK primary care referral mechanism; the GP–patient relationship is important, and trust and rapport are viewed as enablers for patients to engage in referral programs.28 Primary care is best placed to refer patients; GPs have access to practice registers and so can identify retrospective NDH cohorts,29 can refer patients opportunistically and via the NHS Health Checks program and will continue to routinely see patients. NDH and T2D are underdiagnosed nationally6 and still not routinely assessed and coded. Identifying patients within a GP practice for the study increased awareness, diagnosis and referrals. GPs provide continuity of care; there is a seamless transition if patients go onto develop T2D and patients are less likely to be lost to follow-up. The GP referral mechanism into the WWDPP has the potential to have a public health impact at a population level in a relatively short period of time, if scaled up. However, a consideration for clinicians and policymakers is how to engage underrepresented groups such as men, BME and deprived communities.
There are future research opportunities to explore a number of unanswered questions in relation to delivering the best DPP. An RCT to measure the effectiveness of different types of referral routes should be conducted, such as comparing direct to consumer approaches, versus NHS Health Check referrals or primary care referral mechanisms. Analysis should be undertaken to investigate the most effective inclusion criteria, for example, what is the optimal baseline BMI or blood glucose reading for achieving the best results from a DPP. What cohort of patients is a DPP most likely to be effective for? For example, should BME patients, patients with complex mental health needs, vulnerable groups, prisoners, recent migrants, attend specially adapted programs? In-depth analysis into digital technology to prevent T2D is needed. In today’s digital world, research is needed to investigate whether patients would readily accept online delivery of the educational element of the lifestyle intervention and track their lifestyle behavior monitoring via an app.