Population level impact of the NHS Diabetes Prevention Programme on incidence of type 2 diabetes in England: An observational study

Background: The NHS Diabetes Prevention Programme (DPP) is the first nationwide type 2 diabetes prevention programme targeting people with prediabetes. It was rolled out across England from 2016 in three waves. We evaluate the population level impact of the NHS DPP on incidence rates of type 2 diabetes. Methods: We use data from the National Diabetes Audit, which records all individuals across England who have been diagnosed with type 2 diabetes by 2019. We use difference-in-differences regression models to estimate the impact of the phased introduction of the DPP on type 2 diabetes incidence. We compare patients registered with the 3,282 general practices enrolled from 2016 (wave 1) and the 1,610 practices enrolled from 2017 (wave 2) to those registered with the 1,584 practices enrolled from 2018 (final wave). Findings: Incidence rates of type 2 diabetes in wave 1 practices in 2018 and 2019 were significantly lower than would have been expected in the absence of the DPP (difference-in-differences Incident Rate Ratio (IRR) = 0·938 (95% CI 0·905 to 0·972)). Incidence rates were also significantly lower than expected for wave 2 practices in 2019 (difference-in-differences IRR = 0·927 (95% CI 0·885 to 0·972)). These results remained consistent across several robustness checks. Interpretation: Introduction of the NHS DPP reduced population incidence of type 2 diabetes. Longer follow-up is required to explore whether these effects are maintained or if diabetes onset is delayed. Funding: This research was funded by the National Institute for Health and Care Research (Health Services and Delivery Research, 16/48/07 - Evaluating the NHS Diabetes Prevention Programme (NHS DPP): the DIPLOMA research programme (Diabetes Prevention - Long Term Multimethod Assessment)). The views and opinions expressed in this manuscript are those of the authors and do not necessarily reflect those of the NHS, the National Institute for Health and Care Research or the Department of Health and Social Care.