The Programme Development Group (PDG) took account of a number of factors and issues when developing the recommendations.
The PDG considered three types of approach to reducing population and community risk of type 2 diabetes. These were:
a) Individual: focusing on people identified as being at high risk of type 2 diabetes.
b) High-risk population: identifying and targeting communities of people at high risk of type 2 diabetes.
c) Total population: no assessment of risk or targeting of interventions.
The PDG noted that people from lower socioeconomic groups and from some black and minority ethnic communities are at higher risk of type 2 diabetes than the general population. This is due to a set of shared characteristics and behaviours or 'determinants'. Examples include: a higher than average level of overweight and obesity, a higher than average number of people eating a less healthy diet or participating in lower than average levels of physical activity. These groups and communities would collectively benefit from interventions that target the 'shared' risk factors. In addition, more people within these groups and communities (compared with the general population) would benefit from an assessment of their individual risk – and individual interventions to alleviate that risk.
This guidance aims to reduce the risk of type 2 diabetes among populations at particularly high risk. Overweight and obesity is the single biggest risk factor for type 2 diabetes. Since recent estimates (for example, the Foresight report [2007]) suggest that more than half of adults may be obese by 2050, the PDG noted that some of the recommendations would also have a beneficial effect on a large proportion of the general population.
The national NHS Health Check programme identifies and treats individuals at high risk of developing vascular-related diseases including type 2 diabetes. The PDG noted that not all those who are identified as being at risk will choose to change their behaviour or act on the advice. NICE guidance to prevent the progression from pre-diabetes to type 2 diabetes will aim to provide commissioners and practitioners with advice on how they can support people identified as being at high risk through this or other initiatives.
The PDG was mindful that actions to improve the health of the population overall may widen health inequalities between different groups. For example, people from higher socioeconomic groups may be more ready (or able) to change their behaviour than those on a lower income. Therefore, to address health inequalities, it may be necessary to specifically target high-risk groups – even if this is not the most cost-effective option.
Addressing the needs of high-risk communities involves working beyond geographical boundaries. A community is not necessarily a group of people living within a specific geographic location. It might, for example, involve people with shared values or a shared interest. In addition, although people may recognise themselves (and be recognised within a group) as belonging to that group or community, it may not be immediately obvious to 'outsiders'. This can make it difficult to identify and target some of those who may need help to prevent type 2 diabetes. This includes people who are homeless and those who have a disability or a long-term mental health problem. People who are unofficial migrants are another example.
Case studies of ongoing work in the UK, backed up by expert testimony, demonstrated the importance of taking the target group's needs into account from the start. This includes ensuring that any cultural sensitivities are acknowledged.
Trials have shown (Gillies et al. 2007) that behavioural interventions help reduce the likelihood of type 2 diabetes developing among people with pre-diabetes. For example, the Finnish diabetes prevention study (Tuomilehto et al. 2001) showed that the risk of these individuals developing type 2 diabetes is reduced if they achieve one or more of the following:
reduce their weight by more than 5%
keep their fat intake below 30% of energy intake
keep their saturated-fat intake below 10% of energy intake
eat 15 g/1000 kcal of fibre or more
are physically active for at least 4 hours per week.
In addition, a population-based study (Simmons et al. 2006) found an inverse relationship between the number of these goals achieved and the risk of type 2 diabetes developing among the general population. Therefore, the PDG felt that interventions promoting these goals could significantly lower the risk of developing type 2 diabetes among people from lower socioeconomic communities and from black and minority ethnic groups.
The PDG considered systematic reviews of interventions to address the risk factors associated with type 2 diabetes, including high body mass index (BMI), high waist measurement, sedentary lifestyle or poor diet among high-risk groups. The group did not identify any evidence directly related to the prevention of 'pre-diabetes' among black and minority ethnic or lower socioeconomic groups in the UK. Overall, relevant UK-based intervention studies were scarce. Similarly, the evidence on behaviour change among minority ethnic communities was very limited. The data available tended to be based on self-reported measures related to participants' perceptions of the barriers and facilitators to behaviour change. It was not clear whether or not addressing the stated barriers and introducing facilitators would actually result in positive change.
There was no evidence of effectiveness on UK interventions aiming to raise health professionals' awareness of the risk factors for type 2 diabetes or to help them identify groups at high risk. Evidence on the effectiveness of interventions delivered by health professionals and lay workers (such as health trainers) was also lacking.
The potential effect of any intervention may vary according to the risk someone faces of developing type 2 diabetes. However, evidence was not available to assess this theory in practice.
While demonstrating promising results, most of the UK-based community projects considered by the PDG had limited reach. The group felt that they were neither large nor sustainable enough and that they would benefit from being based on established community networks. Staff training for such interventions was another issue.
The PDG developed recommendations through inductive and deductive reasoning, based on the evidence presented in the systematic reviews, expert testimony and its members' knowledge, understanding and experience of the topic area. Due to the scarcity of evidence available, the PDG also drew on existing NICE guidance on: behaviour change, community engagement, obesity, physical activity and cardiovascular disease.
The economic analysis for this work is based on a range of assumptions. The observed effect sizes for individuals, while important, are small and the confidence intervals are large. Most of the interventions considered are estimated to be cost effective (and usually very cost effective). (This assumes that the estimated effect sizes have been used to make the calculation.) The PDG recognised that the bulk of these effects were generally observed only after a number of years.
Economic modelling showed that weight-loss programmes in black and minority ethnic and Asian populations in England that cost £100 per head and yielded an average weight loss of at least 1 kg were cost effective at a cost per quality-adjusted life year (QALY) threshold of £20,000. Interventions that could produce an average weight loss of 3 to 4 kg would be cost-saving.
An intervention programme applied at the population level that resulted in an average weight of loss of 0.25 kg, would be cost effective at the £20,000 threshold if the cost per head of the intervention was £10. A number of the interventions reported in the literature had a per capita intervention cost of this magnitude. The PDG agreed that this analysis justified the recommendation to balance individual-level interventions of large effect aimed at high-risk individuals with cheaper interventions of small effect to individuals that could be cost effective when applied across whole populations.
The PDG recognised that a number of existing activities and programmes aim to help people change their behaviour to prevent a range of diseases and conditions. It acknowledged that these activities and programmes could also help prevent type 2 diabetes and that many have been the focus of earlier NICE guidance. Similarly, the recommendations outlined in this guidance may have an impact on a range of other health conditions (including for example, cardiovascular disease, some common cancers, respiratory diseases and mental wellbeing).
There are many reasons why people who are socially and/or economically disadvantaged can find it more difficult than others to change their behaviour (Swann et al. 2009). The recommendations in this guidance draw on NICE's guideline on behaviour change: general approaches in an attempt to address this inequality. The aim is to create a local environment which encourages people in disadvantaged groups to make change.
The PDG noted the recommendations made in NICE's guideline on obesity. These focus on a range of effective, community-based programmes and stress the importance of ensuring interventions are tailored, long term and address both diet and physical activity. The guideline also outlines strategies for improving diet and increasing physical activity to help prevent obesity and minimise excess weight gain.
The PDG discussed the links between sedentary behaviour and type 2 diabetes – and the need to encourage people to be more physically active. It was aware of evidence to suggest that a sedentary lifestyle may play a more important role than diet in the higher prevalence of type 2 diabetes among black and minority ethnic groups. NICE has published a range of guidance to help the whole population be physically active. The recommendations in this guidance attempt to address specific barriers to physical activity which might face populations at high risk of developing type 2 diabetes. However, more research is needed into how to increase physical activity levels among these groups.
The PDG recognised that the success of interventions can depend on identifying local 'key players' and 'champions' and it looked to recommendations made in NICE's 2008 guideline on community engagement. It noted that, although some community leaders may be able to promote or help deliver type 2 diabetes prevention programmes, not all of them will be willing or able to do so – nor would it always be appropriate.
The PDG acknowledged the need to consider risk factors and vulnerability at all stages of the life course. In particular, it recognised that maternal and early infant nutrition may be important in the prevention of non-communicable diseases such as type 2 diabetes. Interventions aimed at children are also likely to be crucial in reducing the prevalence of type 2 diabetes in the longer term. For example, preventing gestational diabetes and delaying the onset of type 2 diabetes until after childbearing age would reduce the risk of a child getting type 2 diabetes later in life. These issues were beyond the remit of this guidance. However, they are addressed in other NICE guidance.
The PDG were mindful that while the scope for this guidance was adults in high-risk groups, many interventions are delivered in a family setting and these will have benefits for all family members not just adults.
The upper age cut-off point for this guidance (74 years) reflects the age limit of the national NHS Health Check programme. This programme assesses the risk of heart disease, stroke, kidney disease and type 2 diabetes among all adults aged 40–74. It aims to help them reduce or manage their risk by giving them individually tailored advice. (The second piece of guidance will consider interventions among high-risk individuals and groups.)
The PDG did not consider evidence on how specific nutrients or types of diet may reduce the risk of type 2 diabetes, as this falls under the remit of the Scientific Advisory Committee on Nutrition (SACN). As such, it was outside the scope of this guidance. However, the Group supports existing recommendations on healthy eating, as advocated in the 'Eat well' plate (Food Standards Agency 2007).
The PDG was aware of a range of factors that need to be tackled at national and international level to help high-risk groups adopt behaviours that minimise the risk of type 2 diabetes. This includes issues that could be tackled by the food industry, such as the fat content of foods, food labelling, advertising and costs. It also includes issues in relation to the built environment, such as the impact of planning decisions on physical activity levels. The PDG wholeheartedly supported existing NICE recommendations which aim to tackle these issues. It was also mindful that disadvantaged groups may be disproportionately affected and that, as such, any solutions should consider the potential impact on these groups.