Referral to the NHS Diabetes Prevention Programme and conversion from non-diabetic hyperglycaemia to type-2 diabetes mellitus in England: a matched cohort analysis
Rathi Ravindrarajah, Matt Sutton,David Reeves,Sarah Cotterill,Emma Mcmanus, Rachel Meacock,William Whittaker,Caludia Soiland-Reyes, Peter Bower, Evangelos Kontopantelis(2022)
Referral to the NHS Diabetes Prevention Programme and conversion from non-diabetic hyperglycaemia to type-2 diabetes mellitus in England: a matched cohort analysis.
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The NHS Diabetes Prevention Programme (NDPP) is a behaviour-change programme for adults who are at risk of developing Type 2 Diabetes Mellitus (T2DM): people with raised blood glucose levels, but not in the diabetic range, diagnosed with Non-Diabetic Hyperglycaemia (NDH). We examined the effectiveness of referral to the programme at reducing conversion of NDH to T2DM.
Methods & Findings
Clinical Practice Research Datalink data from 1/4/2016 (NDPP introduction) to 31/3/2020 was used. To minimise confounding, we matched patients referred to the programme in referring practices (cases) to patients in non-referring practices (controls). Patients were matched based on age (≥3 years), sex and ≥365 days of NDH diagnosis. Random-effects parametric survival models evaluated the intervention, controlling for numerous covariates. Our primary analysis was selected a-priori: complete case analysis, 1-to-1 practice matching, up to five controls sampled with replacement. Various sensitivity analyses were conducted, including multiple imputation approaches. Analysis was adjusted for age (at index date), sex, time from NDH diagnosis to index date, BMI, HbA1c, total serum cholesterol, systolic blood pressure, diastolic blood pressure, prescription of metformin, smoking status, socioeconomic status,a diagnosis of depression and co-morbidities.
18,470 cases were matched to 51,331 controls in the main analysis. Mean follow-up from referral was 482.0 (SD=317.3) and 472.4 (SD=309.1) days, for cases and controls respectively. Baseline characteristics in the two groups were similar, except cases were more likely to have higher BMI and be ever-smokers. The adjusted HR for cases, compared to controls, was 0.80 (95%CI: 0.73 to 0.87). The probability of not converting to T2DM at 36 months since referral was 87.3% (95% CI: 86.5% to 88.2%) for referred cases and 84.6% (95% CI: 83.9% to 85.4%) for controls. Effectiveness was broadly consistent in the sensitivity analyses, but often smaller in magnitude.
The NDPP was effective in reducing conversion rates from NDH to T2DM. Although we observed lower levels of effectiveness compared to what has been observed in RCTs, this is unsurprising since we examined the impact of referral, rather than attendance or completion of the intervention.
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- Evangelos Kontopantelis
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