Idiopathic inflammatory myopathies (IIM) is a collective name for a group of conditions causing inflammation and weakness of the muscles. This group includes dermatomyositis, juvenile dermatomyositis, and polymyositis. Inclusion body myositis is a related condition with several similar symptoms. In addition to affecting the muscles, some of these conditions can cause a skin rash and some cause problems with internal organs. A person can develop an IIM at any time in their life. The condition can be difficult to diagnose, and symptoms tend to worsen over time.
The number of people in the UK diagnosed and living with an IIM, and the impact of the IIM on their long-term health, is not well known. This study will estimate the number of people in the UK diagnosed with an IIM and see if the age, sex, ethnic background, geography and socioeconomic status of people with an IIM differ to people without an IIM. This project will also compare the number of hospital attendances for people with an IIM and explore whether they face a higher risk of complications, such as cancer and mortality, compared to those people without an IIM. Additionally, we will investigate if symptoms of IIM can be used to help health professionals make earlier diagnosis of IIM.
This study will have clear patient benefit by providing information to support health professionals through raising awareness of these conditions, and supporting improved early diagnosis and treatment of IIM.
Idiopathic inflammatory myopathies (IIM) is a collective name for a group of heterogenous conditions comprising dermatomyositis, juvenile dermatomyositis, polymyositis, inclusion body myositis. There have been limited population-based studies examining IIM. This study will include a detailed characterisation of these conditions’ epidemiology, symptoms and an analysis of comorbid patterns and secondary health resources utilisation in comparison with unaffected controls.
All people (aged ≥2 years) registered in CPRD Aurum since March 2001 whose data quality is considered acceptable for research and with valid linkage to hospital episode statistics, death registration data from the Office for National Statistics, and index of multiple deprivation data, will be eligible. IIM will be identified primarily using coding in HES with additional identification investigated in primary care.
IIM incidence and prevalence will be calculated overall and in sociodemographic subgroups, using a population denominator. To evaluate clinical outcomes, adults with IIM will be disease risk score matched using 1:4 ratio with unaffected controls. Excess all-cause mortality and malignancy will be assessed using adjusted Cox proportional hazards models. Occurrence of immune-mediated inflammatory disease specific comorbidities (interstitial lung disease, dysphagia, myocarditis, common mental health disorders) at IIM diagnosis and within 2 years will be evaluated using adjusted logistic regression. Secondary care utilisation will be evaluated using adjusted Poisson models. The risk for these outcomes in people with IIM vs controls will be compared with the risk for the same outcomes in people with rheumatoid arthritis and systemic lupus erythematosus to assess whether IIM associated risks are comparable to the disease associated risks in these two more studied conditions.
Common IIM symptoms (muscle weakness, joint pain, fatigue, dysphagia, elevated alanine transaminase [if sufficient numbers]) will be evaluated using conditional logistic regression. A descriptive analysis of early symptomatology prior to IIM diagnosis will explore opportunities for improving the timing of IIM diagnosis.
1. Incident IIM overall and by IIM disease subtype: dermatomyositis (DM), juvenile DM, polymyositis (PM), and inclusion body myositis (IBM).
2. All-cause mortality
3. Malignancy (haematological and solid cancers, captured from primary and secondary care records)
4. IIM-specific comorbidities
- ILD (insterstitial lung disease, including cases of pulmonary hypertension)
- dysphagia (including cases of percutaneous endoscopic gastrostomy feeding)
- myocarditis
- common mental health disorders (depression and anxiety)
5. Secondary care healthcare utilisation, comprising secondary care referrals, all-cause emergency department visits (both admitted and non-admitted), hospital admissions, all-cause outpatient appointments (overall and stratified by specialist type), and admissions to high. dependency/intensive care admissions. And Primary care healthcare utilisation comprising of all-cause GP visits and specialist referrals.
6. IIM symptoms comprising muscle weakness, joint pain, fatigue, dysphagia, elevated ALT, estimated from primary and secondary care records.
Michael McLean - Chief Investigator - Pfizer Ltd - UK
Emma Jones - Corresponding Applicant - Momentum Data Ltd
Andrew McGovern - Collaborator - Momentum Data Ltd
Anita Lynam - Collaborator - Momentum Data Ltd
Maciej Czachorowski - Collaborator - Pfizer Ltd - UK
Mary Araghi ( Gerino ) - Collaborator - Pfizer Ltd - UK
Serhan Bahit - Collaborator - Momentum Data Ltd
Andrew Wildman - Collaborator - Momentum Data Ltd
Muhammad (Ashkan) Dashtban - Collaborator - Momentum Data Ltd
HES Accident and Emergency;HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Patient Level Index of Multiple Deprivation