Systemic sclerosis: changes in the incidence rates in the Finnish population during the years 1999–2018

Abstract

Objective

The aim of our study was to examine changes in the incidence of systemic sclerosis (SSc) in Finland using two different classification criteria.

Method

Medical records of patients who had been registered with ICD-10 code M34 from 1999 to 2018 in two university hospitals were reviewed retrospectively. This period was divided into 5 year periods: 1999–2003, 2004–2008, 2009–2013, and 2014–2018. Using American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) 2013 criteria and clinical findings, we reclassified patients into four groups: diffuse SSc, limited SSc, sine SSc, or early SSc. In the same population, we also investigated whether the ACR 1980 criteria were fulfilled.

Results

In 1999–2018, 246 new patients with SSc and 45 patients with early SSc were identified using ACR/EULAR 2013 criteria. Of these patients, 70 fulfilled the ACR 1980 criteria. Using ACR/EULAR 2013 criteria, the increase in new diagnoses was statistically significant when comparing the fourth period with the first period (p = 0.0012). The increase was due to a rise in limited SSc. Mean annual incidence rates in these groups were 0.9, 1.2, 1.9, and 2.8 per 100 000 inhabitants ≥ 16 years old. An increasing trend was also seen when using ACR 1980 criteria, but this was not statistically significant.

Conclusion

The incidence of SSc increased during the period between 1999–2003 and 2014–2018 using ACR/EULAR 2013, but not using ACR 1980 criteria. The increase was detected within a limited SSc subclass, owing to more sensitive classification criteria.

Disclosure statement

SK is an investigator in clinical PsA drug studies funded by AbbVie, Pfizer, and BMS; and has received consulting and speaker fees from Boehringer Ingelheim and scientific meeting attendance support from Roche, Jansen-Cilag, and AbbVie, which are all unrelated to this work. MK and SH have declared no conflicts of interest. JP is an investigator in clinical PsA drug studies funded by Lilly, AbbVie, Pfizer, and BMS; and has received speaker fees from UCB and scientific meeting attendance support from Medac, Jansen-Cilag, and UCB, which are all unrelated to this work. LP is an investigator in clinical PsA drug studies funded by AbbVie, Pfizer, and BMS; and has received consulting and speaker fees from AbbVie, Boehringer Ingelheim, Jansen-Cilag, Novartis Finland, Sandoz, Eli Lilly, and Swedish Orphan Biovirtum, and scientific meeting attendance support from Orion and Sanofi, which are all unrelated to this work. JH has received consulting and speaker fees from Boehringer Ingelheim, AbbVie, Amgen, and Novartis; and scientific meeting attendance support from AbbVie, Medac, Novartis, and Pfizer, which are all unrelated to this work.

Data availability

All data collection and analyses were performed following authorization of two hospital districts. Owing to Finnish legislation to protect data, the register data used in this study cannot be shared without permission from the Health and Social Data Permit Authority of Finland.

Additional information

Funding

This work was supported by research grants from the Finnish Foundation for Rheumatic Diseases to SK and MK, the Turunmaa Duodecim Society to SK, Turku University Hospital Education and Research Foundation to SK, and Tampere Rheumatism Association to MK.