A study published in The Lancet involving 22 million people shows that autoimmune disorders now affect about one in ten individuals. The work points to important socioeconomic, seasonal, and regional differences for several autoimmune disorders and provides new clues on possible causes behind these diseases.
Dr Shivani Misra, supported by the NIHR Imperial BRC, said, “We found that some autoimmune conditions 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.”
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. There are more than 80 known types of autoimmune diseases.
Some of these, 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.
The exact causes of autoimmune diseases remain largely a mystery, particularly whether these are genetically predisposed or driven by modifiable factors. 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 Imperial College London, KU Leuven, University College London, the University of Glasgow, 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 per cent of the population –13 per cent of women and 7 per cent of men. This is higher than previous estimates, which often relied on smaller sample sizes and included fewer autoimmune conditions.
The authors 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.
The research also confirmed that some autoimmune diseases tend to cluster together (ie. one person with a first autoimmune disease is more likely to develop a second autoimmune disease than someone without an 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.
Dr Misra further added, “As a clinician, I frequently see people with autoimmune conditions such as type 1 diabetes and sometimes individuals have more than one autoimmune condition. Up until now, we have not fully understood which autoimmune conditions group together and how age, social factors and gender, affect risk. In this study of 22 million people in the UK, we found that some autoimmune conditions 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.
“We also found evidence of socioeconomic, seasonal, and regional differences for several autoimmune diseases. Such variations are unlikely to be attributable to genetic differences alone and suggest the involvement of potentially modifiable risk factors. We need more research on understanding the shared mechanisms of these autoimmune conditions.”