ACR Meeting Abstracts

ACR Meeting Abstracts

Abstract Number: 1232

Prevalence of Idiopathic Inflammatory Myopathies in Sweden in 2012 – a National Register Study

John Svensson1, Anna Tjärnlund2, Ingrid E. Lundberg3 and Marie Holmqvist4, 1Karolinska Institutet, Stockholm, Sweden, 2Rheumatology Unit, Department of Medicine, Karolinska University Hospital in Solna, Karolinska Institutet, Stockholm, Sweden, 3Medicine, Department of Medicine, Rheumatology Unit, Karolinska University Hospital, Karolinska Institutet S-171 76, Stockholm, Sweden, Stockholm, Sweden, 4Dept of Medicine, Clinical Epidemiology Unit, Dept of Medicine, Karolinska Institutet, Stockholm, Sweden

Meeting: 2015 ACR/ARHP Annual Meeting

Date of first publication: September 29, 2015

Keywords:

Session Information

Date: Monday, November 9, 2015

Title: Epidemiology and Public Health Poster II: Pathogenesis and Treatment of Systemic Inflammatory Diseases

Session Type: ACR Poster Session B

Session Time: 9:00AM-11:00AM

Background/Purpose:

Overall prevalence of idiopathic inflammatory myopathies (IIM) is commonly reported at 10 per 100,000 but worldwide estimates vary between 1 and 25 per 100,000 depending on region, population, sub-diagnosis, methodological considerations and case sources. In this study we aimed at assessing the prevalence of IIM in Sweden on January 1st, 2012, using population-based registers.

Methods:

Linking of multiple national registers was possible using each Swedish resident’s unique personal identification number. Through this linkage we identified all individuals with an inpatient- or non-primary outpatient visit with an ICD-10 code indicating IIM, relevant IIM medication dispensation or registration in the Swedish Rheumatology Quality Register (SRQ).

IIM cases were defined by three progressively strict definitions; (1) liberal requiring ≥1 relevant specialist1 visit, (2) base case requiring ≥2 specialist visits and (3) strict, also requiring dispensation of glucocorticoids or DMARDs. If a patient was registered in the SRQ he/she fulfilled all three definitions.

Prevalence was calculated for respective case definition and stratified by age group, sex, and clinical sub-diagnosis, in addition to county of residence for the base case definition. Corresponding Swedish population as of January 1st2012, retrieved from census data at Statistics Sweden was used in the denominator.

Results:

Overall prevalence varied between 35 (liberal), 19 (base case) and 13 (strict) per 100,000. Using the base case definition, overall female to male ratio was 1.4 and varied between 0.6, for inclusion body myositis (IBM), to 2.6, for juvenile dermatomyositis (JDM). Prevalence per clinical sub-diagnosis was 8, 6, 4, 2 and 1 per 100,000 for polymyositis (PM), unspecified myositis, dermatomyositis (DM), IBM and JDM respectively.

Prevalence increased with age and peaked between 70-79 years (44 per 100,000). Overall women to men ratio was 1,5 and prevalence was highest in women for all age groups except for 70-79 and >80 year groups. Regional variations were observed between the 25 different Swedish counties (between 11 and 24 per 100,000 for Gotland and Västmanland county respectively).

Conclusion:

Estimated prevalence, 19 per 100,000 for the base case definition, was higher than what have been historically reported for IIM but corresponded well to results from recently published register studies. One challenge with this study was to determine which ICD-10 codes correspond to, primarily IIM, but also to correct clinical subgroups.

1 Rheumatologist, neurologist, internal medicine, pediatric-clinic

Disclosure: J. Svensson, None; A. Tjärnlund, None; I. E. Lundberg, None; M. Holmqvist, None.

To cite this abstract in AMA style:

Svensson J, Tjärnlund A, Lundberg IE, Holmqvist M. Prevalence of Idiopathic Inflammatory Myopathies in Sweden in 2012 – a National Register Study [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/prevalence-of-idiopathic-inflammatory-myopathies-in-sweden-in-2012-a-national-register-study/. Accessed .

« Back to 2015 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-idiopathic-inflammatory-myopathies-in-sweden-in-2012-a-national-register-study/