EULAR – the European Alliance of Associations for Rheumatology – works on a broad spectrum of autoimmune and auto-inflammatory diseases. A rise in the incidence of some of these has been described, raising the possibility that incidence might be impacted by environmental factors. But there is a lack of available data, and commonalities and differences between some individual diseases also remain poorly understood.
Conrad and colleagues aimed to clarify the picture by investigating 19 of the most common autoimmune diseases. Their work – shared at the 2023 EULAR congress in Milan, Italy – assesses trends over time, by sex, age, socioeconomic status, season and region, and examines rates of co-occurrence among autoimmune diseases. The researchers used data from the electronic health records of 22 million people in the UK to calculate incidence and prevalence, and then modeled temporal trends and variation.
Between 2000 and 2019, a new diagnosis of one or more autoimmune disease was made in 978,872 people. Taken together the 19 autoimmune disorders studied affected 10.2% of the population – or 13.1% of women and 7.4% of men.
Importantly, age-standardized incidence rates of autoimmune diseases increased by 4% over the study period, with similar rates in both men and women. The largest increases were seen in Graves' disease, coeliac disease, and Sjogren's syndrome, for which incidences have doubled over the past two decades. Over the same period, the incidence significantly decreased for two conditions: Hashimoto's thyroiditis and pernicious anemia.
When the team examined trends in the data, they found a socioeconomic gradient across several diseases, including Graves' disease, pernicious anemia, rheumatoid arthritis, and systemic lupus erythematosus. Seasonal variations were observed for type 1 diabetes and vitiligo, which are more commonly diagnosed in winter and summer, respectively. Regional variations were also observed for a range of conditions.
Autoimmune disorders are commonly associated with each other, particularly Sjogren's, systemic lupus erythematosus, and systemic sclerosis. Patients with type 1 diabetes also have significantly higher rates of Addison's, coeliac, and thyroid diseases, and multiple sclerosis stands out as having low rates of co-occurrence with other autoimmune diseases."
Nathalie Conrad, Department of Public Health and Primary Care, KU Leuven in Belgium
These results suggest that the burden of autoimmune disease continues to increase over time, albeit modestly. One possible factor could be that awareness for some conditions has increased over the study period, alongside improved coding practices and earlier recognition. Another possibility that could be inferred from the socioeconomic, seasonal, and regional disparities observed is that environmental factors could be implicated in disease pathogenesis. The authors also conclude that the interrelations between autoimmune diseases point a finger at shared mechanisms or factors.