Autoimmune diseases occur when the normal role of the immune system in defense against infections is disturbed, resulting in it mistakenly attacking normal healthy cells in the body. Credit: Neuroscience News
Summary: A study of 22 million people found autoimmune disorders now affect around one in 10 individuals, with women more affected than men.
The research also revealed socioeconomic, seasonal, and regional disparities among several autoimmune disorders. The researchers suggest such variations are unlikely to be attributable to genetic differences alone, and may point to the involvement of potentially modifiable risk factors such as smoking, obesity, or stress that contribute to the development of some autoimmune diseases.
The study also confirmed that in some cases, a person with one autoimmune disease is more likely to develop a second, indicating that some autoimmune diseases share common risk factors, such as genetic predispositions or environmental triggers.
Autoimmune diseases affect around 10% of the global population, with 13% of women and 7% of men being affected.
The study used a large dataset of anonymized electronic health records from the UK, covering 22 million people, to investigate 19 of the most common autoimmune diseases.
The research found that there are socioeconomic, seasonal, and regional disparities among several autoimmune disorders and that some autoimmune diseases share common risk factors, such as genetic predispositions or environmental triggers.
Source: Oxford University
A new population-based study of 22 million people shows that autoimmune disorders now affect about 1 in 10 individuals.
The work, published in The Lancet, also highlights 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 defense 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 behavioral changes.
Exact causes of autoimmune diseases, particularly with respect to relative contributions of genetic predisposition or environmental factors, also remain largely a mystery and are 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.
The study used a very large dataset of anonymized electronic health records from the U.K. from 22 million individuals to investigate 19 of the most common autoimmune diseases.
The authors examined whether 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 ranged from 3% to 9% and often relied on smaller sample sizes and included fewer autoimmune conditions.
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 such as smoking, obesity or stress that contribute to the development of some autoimmune diseases.
Finally, their research also confirmed that in some cases a person with one autoimmune disease is more likely to develop a second compared to someone without an autoimmune disease.
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, (Deep Medicine, Nuffield Department of Women’s & Reproductive Health, University of Oxford) commented, “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 generalized 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.”
Dr. Nathalie Conrad is also affiliated with KU Leuven and the University of Glasgow.
Senior author of the paper, Professor Geraldine Cambridge, (University College London) 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.”
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
A rise in the incidence of some autoimmune disorders has been described. However, contemporary estimates of the overall incidence of autoimmune diseases and trends over time are scarce and inconsistent. We aimed to investigate the incidence and prevalence of 19 of the most common autoimmune diseases in the UK, assess trends over time, and by sex, age, socioeconomic status, season, and region, and we examine rates of co-occurrence among autoimmune diseases.
In this UK population-based study, we used linked primary and secondary electronic health records from the Clinical Practice Research Datalink (CPRD), a cohort that is representative of the UK population in terms of age and sex and ethnicity. Eligible participants were men and women (no age restriction) with acceptable records, approved for Hospital Episodes Statistics and Office of National Statistics linkage, and registered with their general practice for at least 12 months during the study period.
We calculated age and sex standardised incidence and prevalence of 19 autoimmune disorders from 2000 to 2019 and used negative binomial regression models to investigate temporal trends and variation by age, sex, socioeconomic status, season of onset, and geographical region in England.
To characterise co-occurrence of autoimmune diseases, we calculated incidence rate ratios (IRRs), comparing incidence rates of comorbid autoimmune disease among individuals with a first (index) autoimmune disease with incidence rates in the general population, using negative binomial regression models, adjusted for age and sex.
Among the 22 009 375 individuals included in the study, 978 872 had a new diagnosis of at least one autoimmune disease between Jan 1, 2000, and June 30, 2019 (mean age 54·0 years [SD 21·4]). 625 879 (63·9%) of these diagnosed individuals were female and 352 993 (36·1%) were male. Over the study period, age and sex standardised incidence rates of any autoimmune diseases increased (IRR 2017–19 vs 2000–02 1·04 [95% CI 1·00–1·09]).
The largest increases were seen in coeliac disease (2·19 [2·05–2·35]), Sjogren’s syndrome (2·09 [1·84–2·37]), and Graves’ disease (2·07 [1·92–2·22]); pernicious anaemia (0·79 [0·72–0·86]) and Hashimoto’s thyroiditis (0·81 [0·75–0·86]) significantly decreased in incidence. Together, the 19 autoimmune disorders examined affected 10·2% of the population over the study period (1 912 200 [13·1%] women and 668 264 [7·4%] men).
A socioeconomic gradient was evident across several diseases, including pernicious anaemia (most vs least deprived area IRR 1·72 [1·64–1·81]), rheumatoid arthritis (1·52 [1·45–1·59]), Graves’ disease (1·36 [1·30–1·43]), and systemic lupus erythematosus (1·35 [1·25–1·46]). Seasonal variations were observed for childhood-onset type 1 diabetes (more commonly diagnosed in winter) and vitiligo (more commonly diagnosed in summer), and regional variations were observed for a range of conditions.
Autoimmune disorders were commonly associated with each other, particularly Sjögren’s syndrome, systemic lupus erythematosus, and systemic sclerosis. Individuals with childhood-onset type 1 diabetes also had significantly higher rates of Addison’s disease (IRR 26·5 [95% CI 17·3–40·7]), coeliac disease (28·4 [25·2–32·0]), and thyroid disease (Hashimoto’s thyroiditis 13·3 [11·8–14·9] and Graves’ disease 6·7 [5·1–8·5]), and multiple sclerosis had a particularly low rate of co-occurrence with other autoimmune diseases.
Autoimmune diseases affect approximately one in ten individuals, and their burden continues to increase over time at varying rates across individual diseases. The socioeconomic, seasonal, and regional disparities observed among several autoimmune disorders in our study suggest environmental factors in disease pathogenesis. The inter-relations between autoimmune diseases are commensurate with shared pathogenetic mechanisms or predisposing factors, particularly among connective tissue diseases and among endocrine diseases.