SAT0707 Trends in the incidence of rheumatoid arthritis in denmark from 1995–2016: a nationwide register-based study
Authors: R.L. Cordtz, P. Højgaard, K. Zobbe, L. Dreyer
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Previous studies have shown conflicting results regarding temporal trends in the incidence of rheumatoid arthritis (RA). <h3>Objectives</h3> To investigate annual incidence rates of RA in Denmark from 1995–2016 using nationwide health care registers, and to explore how these are affected by different case definitions of RA. <h3>Methods</h3> The Danish National Patient Register captures all in- and outpatient (since 1977 and 1994, respectively) contacts at private and public hospitals. Excluding prevalent cases (ICD-8: 712), and using two different case-definitions, we identified all incident RA patients (ICD-10 codes M05.1;3;8;9 and M06.0;8;9) aged ≥18 in each year from 1995–2016, and calculated annual age-standardised incidence rates (per 1 00 000 person years). We used the NORDCAN population for direct standardisation, and the number of adults alive in Denmark at the beginning of each year as the denominator. We furthermore calculated the age- and sex specific incidence rates during the period. Strict case definition: incident patients were required to have at least two in- or outpatient visits at a rheumatology- or general internal medicine clinic/department within 90 days with RA listed as the main diagnosis. Liberal case definition: patients with at least two in- or outpatient contacts listing RA as a main- or contributory diagnosis within 1 year.<sup>1</sup> <h3>Results</h3> We identified 26 090 and 43 080 patients using the Strict and Liberal case definitions, respectively. Patient characteristics according to choice of definition are presented in the Table. The overall incidence rates were 23.7/100,000 person years (23.4–23.9) using the Strict and 39.7/100,000 person years (39.4–40.1) using the Liberal definition. As seen from the figure 1, a slightly increasing trend in RA was observed from 1995 to 2016 independent of choice of case definition, and this increase was more pronounced in 2010. The age-specific incidence rates were highest in women (Strict: 75/100,000 person years; Liberal: 134/100,000 person years) as well as men (Strict: 47/100,000 person years; Liberal: 81/100,000 person years) aged 70–79 years. <h3>Conclusions</h3> We found a slightly increasing trend in the incidence rate of RA from 1995–2016. Further, we found that using the Liberal case definition, the overall and age- and sex specific incidence rates were remarkably similar to those reported from Sweden<sup>1</sup>, whereas the Strict definition resulted in lower incidence rates than previously reported from other countries. <h3>References</h3> [1] Eriksson JK, Neovius M, Ernestam S, et al. Incidence of rheumatoid arthritis in Sweden: A Nationwide population-based assessment of incidence, its determinants, and treatment penetration. Arthritis Care and Research2013;65(6), 870–878. <h3>Disclosure of Interest</h3> R. Cordtz: None declared, P. Højgaard Speakers bureau: UCB and Celgene, K. Zobbe: None declared, L. Dreyer Speakers bureau: UCB and MSD