Epidemiology, autoimmune overlap and in-hospital outcomes of idiopathic inflammatory myopathies in Spain, 1997–2024
Authors' conclusion
IIM hospitalizations doubled over 28 years, driven by IMNM recognition and ageing, with outcomes governed by acute complications and comorbidity rather than subtype. Symptomatic myopathy should be analysed separately and paraneoplastic dermatomyositis unified with idiopathic DM.
Study context
- Population
- Hospital episodes with idiopathic inflammatory myopathies (IIM) in the Spanish hospital-discharge registries (CMBD and RAE-CMBD), 1997–2024episodes (8053 patients in 2016–2024, 9162 earlier), 34,228 (93.2%) were true IIM · patients in 2016-2024 8,053 · patients earlier 9,162
- Participants
- 36,732 episodes
- Exposure
- DM/PM group vs IMNM/Other vs inclusion body myositis (IBM)
- Outcome
- Composition of episodes
Methodological detailspatient-clustered standard errors
- Patient-clustered standard errors
Main finding
As reported in the abstract
- True IIM
- 34 228 (93.2%)
- DM/PM group
- 84.0%
- DM-coded (of DM/PM group)
- 61.4%
- PM-coded (of DM/PM group)
- 35.7%
- Paraneoplastic (of DM/PM group)
- 2.9%
- IMNM/Other
- 13.7%
- IBM
- 2.4%
Observational data: associations, not effects.
Further findings
Hospitalization rate · 1997-2024
- Rose from
- 1.67
- To (per 100 000/year)
- 4.24
- Confined to ages ≥60
- Rates are hospitalization rates, not incidence or prevalence.
Coexisting autoimmune disease
- Coexisting autoimmune disease
- 13.7%
- About one in seven
Mortality
- Mortality (stable)
- 6.1%
Predictors of death
- Advancing age, adjusted OR up to
- 7.97
- C-statistic
- 0.77
- Malignancy, heart failure, interstitial lung disease (ILD), dysphagia and chronic kidney disease
- Apparent protective effects of COPD and diabetes reflected collider bias.
ICU admission in the very elderly
- OR
- 0.21
- Indicating ceiling-of-care de-escalation
Polymyositis (M33.2) coding within the DM/PM group
- Coded as polymyositis (M33.2), within the DM/PM group
- 29.4%
- Declining from
- 40%
- To
- 27%
- More ILD, overlap and antisynthetase features but less malignancy
Original publication
Epidemiology, autoimmune overlap and in-hospital outcomes of idiopathic inflammatory myopathies in Spain, 1997–2024. Rheumatology (Oxford). Published 23 October 2026. doi:10.
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