ArticlesIncidence, 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
Introduction
Autoimmune diseases arise when immune dysregulation causes host tissue damage.1 A wide range of autoimmune diseases are described that present with variable age of onset, tissue distribution, and clinical and functional effects.1 Most of these diseases are incurable and require lifelong treatment.
Adequate public health and service delivery planning requires reliable information about contemporary, population-level disease incidence. However, estimates of autoimmune disease incidence rates and their temporal trends, even in high-income countries, are scarce and inconsistent.1 Some autoimmune disorders, such as type 1 diabetes, are reported to have increased over the past three 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. Even for type 1 diabetes, the incidence of which is among the best studied within autoimmune diseases, reports rely on relatively small cohorts,2, 3 and estimates vary by a factor of ten between studies in Europe alone.4, 5 For many other autoimmune diseases, evidence concerning disease incidence and prevalence is more scarce than for diabetes. The relatively modest absolute numbers of people affected by individual autoimmune diseases is a major challenge to investigators and hinders adequate synthesis across studies.6 As a result, reliable estimates of disease incidence and how they evolve over time, particularly for autoimmune diseases as a group, are not available.
Commonalities and differences between individual diseases are also not well understood and continue to be subject to much research. Although emerging evidence has suggested that autoimmune diseases tend to co-occur within individuals, large-scale investigations across a broad spectrum of autoimmune diseases that could provide clues about shared pathogenesis and risk factors are not currently available.7, 8
To address these knowledge gaps, we analysed a large longitudinal database of primary and secondary care records in the UK that provides information on millions of individuals' diagnoses with several years of follow-up.9, 10 We aimed to investigate the incidence and prevalence for 19 of the most common autoimmune diseases, assess trends over time, by sex, age, socioeconomic status, season, and UK region, and examine rates of co-occurrence among autoimmune diseases.
Section snippets
Data source
In this population-based observational study, we used electronic health records from the GOLD and Aurum datasets of the Clinical Practice Research Datalink (CPRD) from Jan 1, 1985, to June 30, 2019. The CPRD database contains anonymised patient data from approximately 20% of the current UK population and is broadly representative in terms of age, sex, and ethnicity. CPRD is one of the largest databases of longitudinal medical records from primary care in the world and has been validated for
Results
Between Jan 1, 2000, and Dec 31, 2019, a total of 22 009 375 individuals in the CPRD database met study population criteria, with 135 691 152 patient-years of follow-up. Among these individuals, we identified 1 123 789 new diagnoses of autoimmune diseases, affecting a total of 978 872 individuals. The mean age when an autoimmune disease was diagnosed was 54·0 years (SD 21·4), and 625 879 (63·9%) of these individuals were women (table).
The number of people newly diagnosed with one (or more)
Discussion
Our large-scale, population-based study provides several novel insights into the burden of autoimmune disorders, its variation over time, and its variation by individual diseases and patient subgroups of age, sex, and socioeconomic status. Our findings support and extend evidence from previous studies showing an increasing incidence of several autoimmune disorders,20 and show that the increase was particularly pronounced for Graves' disease, coeliac disease, and rheumatic disorders. Our results
Data sharing
Access to CPRD data is conditional on a license agreement and protocol approval process that is overseen by CPRD's Independent Scientific Advisory Committee. A guide to access is provided on the CPRD website (https://cprd.com/data-access).
Declaration of interests
NC is funded by a personal fellowship from the Research Foundation Flanders (grant number 12ZU922N) and declares royalties from Oxford University Innovation. SM is funded by a Wellcome Trust Career Development Award (223024/Z/21/Z) and is supported by the NIHR Imperial Biomedical Research Centre. IBM declares honoraria from AbbVie; grant support paid to his university from AstraZeneca and Eli Lilly; participation on data safety monitoring boards or advisory boards of AstraZeneca, Bristol Myers
References (43)
- et al.
Recent insights in the epidemiology of autoimmune diseases: improved prevalence estimates and understanding of clustering of diseases
J Autoimmun
(2009) - et al.
Autoimmune mechanisms in pernicious anaemia & thyroid disease
Autoimmun Rev
(2015) - et al.
Understanding differences between men and women with axial spondyloarthritis
Semin Arthritis Rheum
(2020) - et al.
Obesity in autoimmune diseases: not a passive bystander
Autoimmunity Reviews
(2014) - et al.
Smoke and autoimmunity: the fire behind the disease
Autoimmunity Reviews
(2016) - et al.
Autoimmune diseases and cardiovascular risk: a population-based study on 19 autoimmune diseases and 12 cardiovascular diseases in 22 million individuals in the UK
Lancet
(2022) - et al.
Autoimmune diseases—connecting risk alleles with molecular traits of the immune system
Nat Rev Genet
(2016) - et al.
Continuous rise in incidence of childhood Type 1 diabetes in Germany
Diabet Med
(2008) - et al.
Recent incidence of type 1 diabetes mellitus in children 0–14 years in Newfoundland and Labrador, Canada climbs to over 45/100,000: a retrospective time trend study
BMC Res Notes
(2012) - et al.
Prevalence and incidence of type 1 diabetes in the world: a systematic review and meta-analysis
Health Promot Perspect
(2020)
Variation and trends in incidence of childhood diabetes in Europe
Lancet
The incidence and prevalence of thyroid autoimmunity
Endocrine
Autoimmune diseases co-occurring within individuals and within families: a systematic review
Epidemiology
Are individuals with an autoimmune disease at higher risk of a second autoimmune disorder?
Am J Epidemiol
Data resource profile: Clinical Practice Research Datalink (CPRD)
Int J Epidemiol
Data resource profile: Clinical Practice Research Datalink (CPRD) Aurum
International Journal of Epidemiology
Global prevalence of ankylosing spondylitis
Rheumatology (Oxford)
The Read clinical classification
BMJ
SNOMED CT
The English Index of Multiple Deprivation 2015: guidance
Essential medical statistics
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Justin Mason died in May, 2022