Evidence that environmental factors such as common infections may be a trigger for diabetes

A major study has added weight to the theory that environmental factors such as common infections may be a trigger for diabetes in children and young adults.

The study, the biggest of its kind, analysed information from a register of over 4,000 people aged 0-29 years old diagnosed with Type 1 diabetes over a 25-year period. The findings for young adults have not been published before.

A quarter of a million people in the UK have Type 1 diabetes, and the number of cases in children is rising by three per cent each year. It develops if the body is unable to produce any insulin and usually appears before the age of 40.

The study authors, from Newcastle and Leeds Universities and Leeds Teaching Hospitals NHS Trust, carried out a sophisticated statistical analysis using information from the register on the times and places where the children and young adults were diagnosed.

A pattern emerged where 'clusters' of cases were found at different geographical locations and time intervals for 10-19 year olds. There were six to seven per cent more cases of Type 1 diabetes found in 10-19 year olds in the clusters than would have been expected by chance.

Females with the condition were more likely to occur in clusters with seven to 14 per cent more cases than expected found in young girls and women aged 10-19 years.

This pattern, which experts call 'space-time clustering', is typical of conditions triggered by infections. Conditions caused by more constant environmental factors produce clusters of cases in one place over a much longer time period.

The results are published in the academic journal Diabetologia and should help towards understanding more about the causes of Type 1 diabetes.

It has previously been suggested that infections are linked to the development of Type 1 diabetes in children who are genetically susceptible to certain environmental triggers.

Lead study author, Dr Richard McNally, of Newcastle University's School of Clinical Medical Sciences (Child Health) said: "This research brings us closer to understanding more about Type 1 diabetes. However, it's just one piece in the jigsaw and much more research is needed before we can identify which infections may be to blame and thus inform advice on preventative measures.

"The condition is likely to be caused by an interplay of factors, of which infections are just one element."

The study used data on 4008 0-29 year olds from the Yorkshire Register of Diabetes in Children and Young People from 1978-2002, which receives funding from the Department of Health.

Dr Richard Feltbower, Co-researcher and Research Statistician from the Paediatric Epidemiology Group at the University of Leeds said: "This research is based on a unique register of patients diagnosed with Type 1 diabetes and the results for young people are entirely new. The clusters may occur as a result of infections precipitating the condition in already predisposed individuals."

Simon O'Neill, Director of Care and Policy at Diabetes UK, said: "We always suspected that common infections could be a trigger for Type 1 diabetes in those who are already genetically susceptible. This research provides vital evidence in supporting this link.

"The fact that the number of cases of Type 1 diabetes is rising by three per cent each year cannot be explained by genetics alone. This research reinforces the idea that common infections and environmental factors also play a part."