Incidence and prevalence of rheumatoid arthritis in Denmark from 1998 to 2018: a nationwide register-based study

Abstract

Objective

To investigate the incidence and prevalence of rheumatoid arthritis (RA) in the adult Danish population.

Method

In this nationwide register-based cohort study, patients with incident RA between 1998 and the end of 2018 were identified using Danish administrative registries. The age- and sex-standardized incidence rate (IR), incidence proportion (IP), lifetime risk (LR), and point prevalence (PP) of RA were calculated. RA was defined as a first-time RA diagnosis registered in the Danish National Patient Registry combined with a redeemed prescription of a conventional synthetic disease-modifying anti-rheumatic drug in the following year. In addition, three different case definitions of RA were explored.

Results

The overall age- and sex-standardized IR of RA from 1998 to 2018 was 35.5 [95% confidence interval (CI) 35.1–35.9] per 100 000 person-years while the IP was 35.2 (95% CI 34.8–35.5) per 100 000 individuals. The IR was two-fold higher for women than for men. The LR of RA ranged from 2.3% to 3.4% for women and from 1.1% to 1.5% for men, depending on the RA case definition used. The overall PP of RA was 0.6% (95% CI 0.5–0.6%) in 2018: 0.8% (95% CI 0.7–0.8%) for women and 0.3% (95% CI 0.3–0.4%) for men. The prevalence increased about 1.5-fold from 2000 to 2018.

Conclusion

The IR and PP were approximately two-fold higher for women than for men. The prevalence of RA in Denmark increased significantly from 2000 to 2018. The RA case definition had more impact on the results than the choice of denominator.

Acknowledgements

A patient research partner was included in the development of the protocol and had the opportunity to submit comments to the protocol. The authors thank the patient research partner for her contribution.

Disclosure statement

Dr. Soussi reports grants from The Danish Rheumatism Association, grant from Aase and Ejnar Danielsens Foundation, during the conduct of the study. Dr. Cordtz has nothing to disclose. Dr. Kristensen has nothing to disclose. Dr. Bork has nothing to disclose. Dr. Christensen has nothing to disclose. Dr. Schmidt has nothing to disclose. Dr. Torp-Pedersen reports grants from Bayer, grants from Novo Nordisk, outside the submitted work. Dr. Prieto-Alhambra reports grants and other from AMGEN, grants, non-financial support and other from UCB Biopharma, grants from Les Laboratoires Servier, outside the submitted work; and Janssen, on behalf of IMI-funded EHDEN and EMIF consortiums, and Synapse Management Partners have supported training programmes organised by DPA's department and open for external participants. Dr. Dreyer reports grants from BMS, other from Galderma, other from Eli Lilly, outside the submitted work.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the Aase og Ejnar Danielsens Fond [19-10-0295]; Danish Rheumatism Association [R172-A6090,R175-A6091,R186-A6573].