Diabetes meets many of the criteria for screening. A high proportion of people have undiagnosed diabetes, many individuals present with complications when they are diagnosed, and there is a long “latent” period between when the disease starts and when a person experiences symptoms and presents at their GP. People with diabetes have an increased risk of developing cardiovascular disease (heart attack or stroke). It is logical to suggest that if we found people earlier in the disease trajectory and treated them before symptoms developed, that we could reduce the risk of them suffering from an early death or experiencing a heart attack or stroke. However, there is little evidence to support this idea, and there are a number of uncertainties concerning the potential benefits of population-based screening for type 2 diabetes
The Anglo-Danish-Dutch Study of Intensive Treatment In People with Screen Detected Diabetes in Primary Care (ADDITION study) was set-up in 2001 to answer some of these uncertainties. The study consists of a screening phase followed by a pragmatic trial of intensive treatment compared to routine care in four centres (Denmark, Cambridge UK, the Netherlands and Leicester UK).
Following screening in 343 practices, 3,057 eligible participants with screen-detected diabetes agreed to take part in the ADDITION treatment trial. In Cambridge, confirmation of the diagnosis of diabetes and baseline assessments were carried out in our clinical research facilities in Ely, Wisbech and Addenbrooke’s with additional measurements in Peterborough and Huntingdon. As a result of the screening programme 867 people in the East Anglia region were made aware that they had diabetes.
Half of the patients diagnosed with type 2 diabetes in the ADDITION study went on to receive standard care for type 2 diabetes from their general practice following national guidelines. The other half received an intensive treatment programme to reduce their risk of cardiovascular disease.
This treatment included:
- educational materials designed to help patients to improve their diet, increase their physical activity and stop smoking.
- increased use of medication to reduce levels of cardiovascular risk factors such as blood glucose, blood pressure and cholesterol.
More information can be found here: www.addition.au.dk
We invited the two groups of patients back to our testing sites for a health assessment after one and five years. We compared the two groups to assess whether the intensive treatment programme reduced the risk of developing cardiovascular disease and which approach patients preferred.
What have we found?
- Screening for diabetes does not make people feel anxious, depressed or falsely reassured.
- The health status of ADDITION participants was improved five years after diagnosis e.g. there were important reductions in levels of blood pressure, cholesterol and blood glucose over the five years of the study.
- Earlier diagnosis and treatment of diabetes has contributed to lower than expected rates of heart attacks and premature death, which are now similar to those in the general population without diabetes.
Study results were recently published in the Lancet medical journal, which can be found here.
ADDITION plus is a sub-study that involves patients within the intensive treatment programme of the ADDITION study and patients with diabetes recently diagnosed by their GP. In addition to their treatment programme, half of the patients were given additional support and advice aimed to help them keep to their programme of lifestyle changes and medication. The other half of the patients were not given any additional support. Behaviour change in each group was then measured after one year and five years.
Unit involvement in ADDITION is funded by MRC core funding, plus grant support: Wellcome Trust (grant reference no: G061895), the Medical Research Council (grant reference no: G0001164), the NIHR Health Technology Assessment Programme (grant reference no: 08/116/300), National Health Service R&D support funding (including the Primary Care Research and Diabetes Research Networks) and the National Institute for Health Research [RP-PG-0606-1259].