Epidemiology of idiopathic inflammatory myopathies: a population-based cohort in England, 2002–2021
Authors' conclusion
There are major demographic differences in IIM incidence, notably by sex and ethnicity.
Study context
- Population
- All patients (aged >2 years) in England registered in Clinical Practice Research Datalink (CPRD) Aurum, 1 March 2002 to 31 March 2021incident cases by subtype
- Participants
- 1,590 / 432 / 2,083
- Exposure
- Dermatomyositis (DM) vs inclusion body myositis (IBM) vs Other idiopathic inflammatory myopathies (IIM)
- DMn = 1,590
- IBMn = 432
- Other IIMn = 2,083
- Outcome
- Incidence of three main IIM subtypes: DM, IBM and other IIM
Methodological detailsprimary care database (CPRD Aurum) with linkage to hospital episode data, Poisson models
- Primary care database (CPRD Aurum) with linkage to hospital episode data
- Poisson models
Main finding
As reported in the abstract
Incidence per 100 000 person-years
Observational data: associations, not effects.
Further findings
| Outcome | aIRR (95% CI) | |
|---|---|---|
| Incidence by sex (females vs males)Females (DM)vs Males (DM) | 1.84 (1.66–2.04) | |
| Incidence by sex (females vs males)Females (other IIM)vs Males (other IIM) | 1.09 (1.00–1.19) | |
| Incidence by sex (females vs males)Females (IBM)vs Males (IBM) | 0.73 (0.60–0.89) | |
| Incidence by ethnicity (vs white) | 2.80 (2.32–3.37) | |
| 0.20.5125Adjusted incidence rate ratio (log scale) |
Point prevalence at study end
Incidence by ethnicity (vs white)
- South Asian, black, other and unknown ethnic groups had a higher incidence of DM and other IIM vs white ethnicity
Original publication
Epidemiology of idiopathic inflammatory myopathies: a population-based cohort in England, 2002–2021. RMD Open. Published 15 July 2026. doi:10.
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