Diabetes Distilled: Pre-diabetes progression risk can help prioritise prevention support

Although everyone diagnosed with pre-diabetes should be offered referral to the Healthier You: NHS Diabetes Prevention Programme or our local intensive lifestyle change programme, being aware of progression risk amongst different groups allows us, if needed, to target our limited resources to where we can hope to make the biggest impact on preventing new diagnoses of type 2 diabetes. The risk information may also be helpful in motivating people to make lifestyle changes to reduce their risk of progression and to stay diabetes-free.

Although those of South Asian and South-East Asian ethnicity are known to be at greater risk of developing type 2 diabetes at an earlier age, and of more rapid progression of complications, compared with white Europeans, little is known on how ethnicity influences progression from pre-diabetes to type 2 diabetes. Likewise, people living with the most socioeconomic deprivation are at greater risk of developing type 2 diabetes than those in less deprived groups, but again it is not clear how deprivation influences progression from pre-diabetes to type 2 diabetes.

This retrospective cohort study, published in Diabetic Medicine, explored the risk of progression to type 2 diabetes amongst nearly 400000 people with pre-diabetes diagnosed between January 2005 and December 2017, who were captured in The Health Improvement Network (THIN) UK primary care database. The progression data were explored by ethnicity, (white European, South Asian, mixed-race, Black and other), deprivation index (quintiles based on the Townsend score), age (18 to <30, 30 to <40, 40 to <65 and ≥65 years) and weight (normal/underweight, overweight and obese).

Results

Overall, progression rates from pre-diabetes to type 2 diabetes were low, even in groups with the highest risk of type 2 diabetes. People from South Asia and those of mixed race, but not Black people, had higher progression risk than those of white European ethnicity. Surprisingly, both younger age groups (<40 years) and older people (≥65 years) had lower adjusted hazard ratios (HRs) than those aged 40 to <65 years (the reference group). Those in the higher quintiles of deprivation had higher adjusted HRs than those in the least deprived group but, when explored by ethnicity, social deprivation was only associated with increased progression in white Europeans and not other ethnicities. Weight is known to be a risk factor for progression, and in this study the adjusted HRs were very significantly increased for those with overweight and obesity compared with normal/underweight people. This trend was observed across all the ethnicities studied. Additional detail on the incident rates and adjusted HRs are shown in Table 1.

The authors propose that the increased risk observed in South Asians could be associated with the increased biological susceptibility to developing type 2 diabetes at an earlier age in this group, increased insulin resistance and more rapid decline of beta-cell function, as well as increased visceral and abdominal fat deposition compared with white European people at the same BMI (Iliodromiti et al, 2023). Lifestyle factors may also contribute, as South Asian people overall have been identified to be less physically active and to eat diets higher in carbohydrates and saturated fats than white Europeans (Gujral et al, 2013). The authors also postulate that behavioural factors, poor living conditions, poor availability of healthy foods and, particularly, unemployment contributing to chronic stress, anxiety and unhealthy food choices may all play a role in the increasing progression rates associated with deprivation in the white European group observed in this study.

Strengths of the study are that it was performed on a UK database, using UK parameters for pre-diabetes (HbA_1c between 42 and 48 mmol/mol) and including a large population with different ethnicities represented. The THIN database captures around 6% of the UK population, is generalisable to the UK population and has the same age structure as the population as a whole. Limitations include that ethnicity was only recorded for 51% of the study cohort. However, BMI and deprivation data were consistent when examined in cohorts with and without recorded ethnicities.

Implications for practice

It is important that those developing and running prevention programmes try to ensure they are meeting the needs of these groups at the highest risk of progression. Early data from the NHS Diabetes Prevention Programme showed it was effective, with a mean weight reduction of 2.3 kg and an HbA_1c reduction of 1.26 mmol/mol overall, and mean reductions of 3.3 kg and 2.04 mmol/mol among those who completed the programme (Valabhji et al, 2020). Although these numbers seem small, they are likely to make an impact on progression. In response to lower attendance and completer rates in some high-risk groups, including certain ethnicities, the NHS piloted a digital diabetes prevention programme in nine areas of England. Early outcomes confirmed a mean weight loss of 3.1 kg and a 1.6 mmol/mol reduction in HbA_1c at 12 months (Ross et al, 2022). As well as offering referral to the NHS Diabetes Prevention Programme in England or similar programmes in the devolved UK nations, the authors remind us to be aware of these differing progression risks, so that we can ensure we prioritise the highest-risk groups. It is hoped this study will help to inform our practice and prioritise prevention of progression from pre-diabetes to type 2 diabetes even when workload is high and resources are tight.