Secular trends of sustained remission in rheumatoid arthritis, a nationwide study in Sweden.

Objectives: The aim of this study of patients with RA in Sweden was to investigate secular trends in achieving sustained remission (SR), i.e. DAS28 <2.6 on at least two consecutive occasions and lasting for at least 6 months.

Methods: All adult RA patients registered in the Swedish Rheumatology Quality register through 2012, with at least three registered visits were eligible, a total of 29 084 patients. Year of symptom onset ranged from 1955, but for parts of the analysis only patients with symptom onset between 1994 and 2009 were studied. In total, 95% of patients fulfilled the ACR 1987 classification criteria for RA. Odds of reaching SR for each decade compared with the one before were calculated with logistic regression and individual years of symptom onset were compared with life table analysis.

Results: Of patients with symptom onset in the 1980s, 1990s and 2000s, 35.0, 43.0 and 45.6% reached SR, respectively (P < 0.001 for each increment), and the odds of SR were higher in every decade compared with the one before. The hazard ratio for reaching SR was 1.15 (95% CI 1.14, 1.15) for each year from 1994 to 2009 compared with the year before. Five years after symptom onset in 2009, 45.3% of patients had reached SR compared with 15.9% in 1999.

Conclusion: There is a clear secular trend towards increased incidence of SR in patients with RA in Sweden. This trend most likely reflects earlier diagnosis and treatment start, and adherence to national and international guidelines recommending the treat to target approach.