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Between 2000 and 2019, age-standardized incidence rates of autoimmune diseases increased by 4%.
Autoimmune diseases currently affect about 1 in 10 individuals in the United Kingdom (UK), which has continued to steadily increase over time, according to data presented at the European Congress of Rheumatology (EULAR) 2023.1 Investigators noted that environmental factors, such as socioeconomic, seasonal, and regional disparities among several autoimmune disorders, may play a role in disease pathogenesis. Among connective tissue diseases and endocrine diseases, the connections between autoimmune diseases are linked to shared pathogenetic mechanisms or predisposing factors.
“A rise in the incidence of selected autoimmune disorders has been described, raising the question as to whether the overall incidence of autoimmune disorders might be on the rise due to environmental factors,” stated lead investigator Nathalie Conrad, PhD, from the Department of Public Health and Primary Care at KU Leuven, Belgium, and colleagues. “However, reliable estimates of disease incidence and trends over time, particularly as pertains to autoimmune diseases as a group, are not available. Commonalities and differences between individual diseases also remain poorly understood.”
To determine the incidence and prevalence of common autoimmune diseases, examine rates of co-occurrence among these diseases, and to evaluate trends over time using seasonal, regional, socioeconomic, sex, and age data, investigators utilized the electronic health records of 22 million individuals from the Clinical Practice Research Datalink (CPRD).
For more than 30 years, the CPRD database, a real-world research service supporting retrospective and prospective public health and clinical studies, has collected anonymous patient data from a network of practices across the UK. The primary care data, which is representative of the UK population health dataset, are linked to a variety of other health related data, resulting in a longitudinal, generalizable, health dataset.2
The incidence and prevalence of 19 autoimmune disorders between 2000 and 2019 were calculated and negative binomial regression models further analyzed potential trends. Incidence rate ratios comparing comorbid autoimmune conditions among the general population and those with a first autoimmune disease were calculated to determine the co-occurrence of the conditions, adjusted for sex and age.
Of the 22,009,375 individuals ultimately included in the analysis, 978,872 patients were newly diagnosed with at least 1 autoimmune disease during the study period. The mean age of patients was 54.0 years and 64% were female. The autoimmune disorders analyzed affected 10.2% of individuals during the study period (13.1% of women and 7.4% of men).
Throughout the study period, age-standardized incidence rates of autoimmune diseases increased by 4%, with similar rates observed for men and women. The largest increases were reported in Sjogren’s syndrome, celiac disease, and Graves’ disease, which have doubled over the past 2 decades. However, Hashimoto’s thyroiditis and pernicious anemia have exhibited a significant decrease in incidence.
A socioeconomic gradient was observed in rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Graves’ disease, and pernicious anemia. Seasonal variations were reported for type 1 diabetes, which is more frequently diagnosed in the winter, and vitiligo, which is more frequently diagnosed in the summer.
Autoimmune disorders were commonly associated with each other, particularly Sjogren’s, systemic lupus erythematosus, and systemic sclerosis. Individuals with type 1 diabetes had significantly higher rates of celiac, Addison’s, and thyroid diseases. Conversely, a multiple sclerosis diagnosis had low rates of co-occurrence with other autoimmune diseases.
Albeit modestly, results indicated that the burden of autoimmune disease has continued to rise over time. However, investigators noted that a factor responsible for this escalation could be the increase in awareness of some conditions over the study period, as well as earlier diagnosis and improved coding practices.