New population-based study led by UCL and the University of Oxford shows that autoimmune disorders are more common than previously thought.
The research, published in The Lancet, estimates that around one in ten individuals in the UK now live with an autoimmune disorder. The findings also highlight important socioeconomic, seasonal and regional differences for several autoimmune disorders, providing new clues as to what factors may be involved in these conditions.
Autoimmune diseases occur when an issue causes the immune system to mistakenly attack normal healthy cells in the body. T here are more than 80 known autoimmune diseases, including conditions like rheumatoid arthritis, type 1 diabetes and multiple sclerosis.
Some autoimmune disorders, such as type 1 diabetes, are reported to have increased in recent decades. This has raised the question whether overall incidence of autoimmune disorders is on the rise and what factors are involved, such as environmental factors or behavioural changes in society. The exact causes of autoimmune diseases remain largely unknown, including how much can be attributed to a genetic predisposition to disease and how much is down to exposure to environmental factors.
A consortium of researchers from KU Leuven, UCL, the University of Glasgow, Imperial College London, Cardiff University, the University of Leicester, and the University of Oxford came together to answer some of these questions. The group included experts in epidemiology, biostatistics, rheumatology, endocrinology and immunology.
The study used anonymised electronic health data from 22 million individuals in the UK to investigate 19 of the most common autoimmune diseases. The authors examined whether incidence of autoimmune diseases is rising over time, who is most affected by these conditions and how different autoimmune diseases may co-exist with each other.
They found that the 19 autoimmune diseases studied affect around 10% of the population. This is higher than previous estimates, which ranged from 3-9% and often relied on smaller sample sizes and included fewer autoimmune conditions. The analysis also highlighted a higher incidence in women (13%) than men (7%).
The research discovered evidence of socioeconomic, seasonal and regional disparities for several autoimmune disorders, suggesting that these conditions are unlikely to be caused by genetic differences alone. This observation may point to the involvement of potentially modifiable risk factors such as smoking, obesity or stress. It was also found that in some cases a person with one autoimmune disease is more likely to develop a second, compared to someone without an autoimmune disease.
Dr Nathalie Conrad, (Nuffield Dept of Women’s & Reproductive Health, University of Oxford), 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."
These findings reveal novel patterns that will inform the design of further research into the possible common causes of different autoimmune diseases.
Professor Geraldine Cambridge (UCL Medicine) said: "Our study highlights the considerable burden that autoimmune diseases place upon individuals and the wider population. Disentangling the commonalities and differences within this large and varied set of conditions is a complex task. There is a crucial need, therefore, to increase research efforts aimed at understanding the underlying causes of these conditions, which will support the development of targeted interventions to reduce the contribution of environmental and social risk factors."
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