A new population-based study, involving 22 million people, shows that autoimmune disorders now affect around one in ten individuals. The work, which is published in The Lancet, further shows important socioeconomic, seasonal, and regional differences for several autoimmune disorders and provides new clues on possible causes behind these diseases.
Autoimmune diseases occur when the normal role of the immune system in defence against infections is disturbed resulting in it mistakenly attacking normal healthy cells in the body. Examples of such diseases include Rheumatoid arthritis, Type 1 diabetes and Multiple sclerosis and there are more than 80 types of autoimmune diseases known.
Some autoimmune disorders, such as Type 1 Diabetes, are reported to have increased over the past several decades, raising the question as to whether the overall incidence of autoimmune disorders is on the rise, driven perhaps by common environmental factors or behavioural changes. Exact causes of autoimmune diseases, particularly whether these are genetically predisposed or driven by modifiable factors, also remain largely a mystery and is subject to much research. Because individual autoimmune diseases are rare, and because there are so many different types of autoimmune diseases, it has been very difficult to undertake sufficiently large studies and establish reliable estimates to answer these questions.
A consortium of experts in epidemiology, biostatistics, rheumatology, endocrinology, and immunology, from KU Leuven, University College London, the University of Glasgow, Imperial College London, Cardiff University, the University of Leicester, and the University of Oxford, have come together to answer some of these questions. Their study used a very large dataset of anonymized electronic health records from the UK from 22 million individuals to investigate 19 of the most common autoimmune diseases – and to examine if cases of autoimmune diseases are rising over time, who is most affected by these conditions and how different autoimmune diseases may co-exist with each other.
They found that, taken together, these 19 autoimmune diseases studied affect about 10% of the population –13% of women and 7% of men. This is higher than previous estimates, which often relied on smaller sample sizes and included fewer autoimmune conditions, and shows how important it is to study autoimmune diseases and to better understand their causes and treatments.
They also found evidence of socioeconomic, seasonal, and regional disparities among several autoimmune disorders. They suggest that such variations are unlikely to be attributable to genetic differences alone and may point to the involvement of potentially modifiable risk factors contributing to the development of some autoimmune diseases.
Finally, their research also confirmed that some autoimmune diseases tend to cluster together (for example, one person with a first autoimmune disease is more likely to develop a second autoimmune disease than someone without autoimmune disease), however at a much larger scale and for a much larger set of autoimmune diseases than previous studies. These findings reveal novel patterns that will likely inform the design of further research on possible common causes behind different autoimmune disease presentations.
First author of the paper Dr Nathalie Conrad, based at the KU Leuven in Belgium, and an Honorary Research Fellow at the University of Glasgow, said: “We observed that some autoimmune diseases tended to co-occur with one another more commonly than would be expected by chance or increased surveillance alone. This could mean that some autoimmune diseases share common risk factors, such as genetic predispositions or environmental triggers. This was particularly visible among rheumatic diseases and among endocrine diseases. But this phenomenon was not generalised across all autoimmune diseases – multiple sclerosis for example, stood out as having low rates of co-occurrence with other autoimmune diseases, suggesting a distinct pathophysiology.”
Co-author on the paper, Professor Iain McInnes, Vice-Principal of the University of Glasgow and Head of the College of Medical, Veterinary & Life Sciences, said: “This remarkable report documents changing patterns of immune diseases over two decades in the UK. These conditions pose a huge burden on individuals and upon wider society and currently represent an enormous unmet clinical need. This pioneering study provides invaluable insights that will inform improved understanding of immune diseases and their treatments going forward.”
Senior author of the paper, Prof Geraldine Cambridge, University College London said: “Our study highlights the considerable burden that autoimmune diseases bring upon individuals and the wider population and the complexity of disentangling commonalities and differences within this large and heterogenous set of conditions. There is a crucial need therefore for recognising the importance of increasing research efforts that might help to elucidate underlying pathophysiological mechanisms and support the development of targeted prevention measures such as those to reduce the contribution of environmental and social risk factors.”
The full study can be read here: “Incidence, prevalence, and co-occurrence of autoimmune disorders over time and by age, sex, and socioeconomic status: a population-based cohort study of 22 million individuals in the UK.”
