A large study of almost 39,000 patients shows clear differences between European countries. In wealthier countries, patients started treatment earlier – but also switched more quickly.
The patients in the study had psoriatic arthritis or axial spondyloarthritis. Psoriatic arthritis causes inflammation in the joints of people with psoriasis. Axial spondyloarthritis causes inflammation and pain in the back and pelvis in particular.
In wealthier countries, patients received advanced treatment earlier in the course of their disease. They also had less active disease when treatment began.
At the same time, they more often stopped taking the medication or switched to another treatment earlier than patients in countries with lower gross domestic product (GDP) per capita.
It may seem strange. But staying on the same medication for a long time is not always a sign of better treatment. And an early switch does not always mean that the treatment has not worked.
“We saw that the disease and the course of treatment varied between countries. Therefore, we wanted to investigate whether economics and other conditions in the countries could explain some of the differences,” says first author Brigitte Michelsen.
She is a rheumatologist and researcher affiliated with REMEDY at Diakonhjemmet Hospital, Sørlandet Hospital and Rigshospitalet in Copenhagen.
The study is published in the Annals of the Rheumatic Diseases and includes around 39,000 patients from 13 European countries.
Looked at how long patients used the same medication
In psoriatic arthritis and axial spondyloarthritis, the immune system can create inflammation in the body. If conventional treatment does not work well enough, patients can be given biologic drugs that can reduce inflammation more effectively.
Such drugs can have a good effect, but they are often expensive.
The researchers examined how many people were still using the same biologic medicine after 6, 12 and 24 months. They also looked at how active the disease was when treatment started.
The data came from EuroSpA, a European collaboration of registries for patients with these diseases. The patients started treatment between 2015 and 2022.
The countries were divided into three groups according to GDP per capita. The division only applied to the countries in this study. Therefore, it does not say that any of the countries are generally “rich” or “poor”.
Norway was in the group with the highest GDP along with Switzerland, Denmark and Iceland. Estonia, Portugal, Romania and Slovenia were in the group with the lowest GDP. The Czech Republic, Spain, Italy and Finland were in the middle. The United Kingdom was only included for patients with axial spondyloarthritis.
The researchers also looked at other measures of a country's resources, including health spending, income, and the Human Development Index.
81 versus 65 percent still used the same treatment
The differences were clear.
Among patients with psoriatic arthritis, 81 percent in countries with the lowest GDP were still using the first medication after one year. In countries with the highest GDP, the figure was 65 percent.
For patients with axial spondyloarthritis, the figures were 86 and 69 percent.
The same trend was repeated after 6, 12 and 24 months. It applied to both women and men, and to both initial and subsequent treatments. The association was strongest in women with axial spondyloarthritis.
But a shorter time on the same medication does not mean that the treatment is worse.
More choices can make switching easier
In countries with good access to treatment, patients can receive advanced treatment earlier. Doctors may also have more medications to choose from.
If the first medication does not work well enough, or causes side effects, it may be easier to switch.
In countries with fewer rheumatologists and fewer treatment options, it can be more difficult. Co-payments and stricter regulations can also play a role. Patients may therefore be left on the same medication for longer.
The researchers therefore believe that the time spent on the same medicine not only says something about the medicine itself. It can also say something about how the health service is structured, and what choices patients and doctors have.
The most common reasons for stopping were lack of efficacy and side effects. Both were recorded more often in countries with the highest GDP. Few stopped because the disease was in remission.
The researchers also point to a possible disadvantage of easy access to many treatments. If the threshold for starting is low, some people may receive treatment even if their symptoms are not primarily due to inflammation.
Then the medication may have little effect on the symptoms, and the patient may end up changing treatment again.
The study cannot confirm that this is the explanation. The researchers point to several possible reasons.
More illness at start of treatment in countries with lower GDP
The second main finding was about how sick the patients were when treatment started.
Patients in countries with lower GDP had more active disease when they started advanced treatment. This was particularly evident in psoriatic arthritis.
Patients in wealthier countries had also had the diagnosis for a shorter period of time when treatment began.
This may indicate that some patients may have to wait longer or have more active disease before they can access such treatment.
The differences between countries therefore do not have to be solely due to medical factors. Economics, regulations and the way the health service is organized may also play a role.
"Although we have received more and more good treatments, the resources in the health services still vary from country to country. The findings show how important it is that patients receive effective treatment in a timely manner, while at the same time expensive treatments are used in a good way," says Michelsen.
Different challenges
The results point to various possible challenges.
Countries with fewer resources may need to detect high disease activity earlier. They may also need better access to effective treatment.
In countries with greater resources, the challenge may be to ensure that frequent changes actually benefit the patient.
- For doctors and health policymakers, the results show how important it is to provide equal access to effective treatment, regardless of which country you live in, says Michelsen.
Shows correlations – not causation
According to the researchers, this is the first study of these diseases that looks at both the countries' economies, disease activity at the start of treatment, and how long patients use the same treatment.
One strength of the study is that it is large. Almost 39,000 patients from different parts of Europe were followed for up to two years. However, it has some limitations:
The register study can show that conditions are related, but not that a country's economy is the cause of the differences.
A rich country also does not only have rich residents. The study could not examine economic differences between people in the same country.
Since all countries were European, the results cannot be readily applied to other parts of the world.
– Even with the limitations of the registry study, we see a clear pattern that is interesting for both practitioners and patients, says Michelsen.
Facts about the study
The study: Influence of national socioeconomic status on treatment retention and disease activity in psoriatic arthritis and axial spondyloarthritis: evidence over 2 years in 13 European countries, Brigitte Michelsen et al., Annals of the Rheumatic Diseases, 2026.
The study was conducted under the auspices of the European Spondyloarthritis Research Collaboration Network (EuroSpA). Norwegian data came from NOR-DMARD. The study was financially supported by Novartis. According to the researchers, the sponsor had no influence on the data, analyses, manuscript or the decision to publish.
· The study includes 38,911 patients from 13 European countries: 17,296 with psoriatic arthritis and 21,615 with axial spondyloarthritis.
· This is a registry study. The researchers used information from patients who received routine treatment in the health service.
· Patients started biologic or targeted synthetic disease-modifying drugs during the period 2015–2022.
· The researchers examined how long the patients continued with the same treatment after 6, 12 and 24 months, and how active the disease was when treatment started.
· The countries were compared based on, among other things, GDP per capita, health spending, gross national income and the Human Development Index.
· The countries were divided into three groups with lower, middle and higher GDP within the countries that participated in the study. This is not a general division into rich and poor countries.
· Norway, along with Switzerland, Denmark and Iceland, was in the group with the highest GDP per capita in this study.
· The study was conducted through the European research collaboration EuroSpA and published in the Annals of the Rheumatic Diseases.
· The study shows connections between national conditions and treatment, but cannot determine that the country's economy itself is the cause of the differences.
· The research is based on data from these registries
ATTRA (Czech Republic), DANBIO (Denmark), ESRBTR (Estonia), ROB-FIN (Finland), ICEBIO (Iceland), GISEA (Italy), NOR DMARD (Norway), Reuma.pt (Portugal), RRBR (Romania), biorx.si (Slovenia), BIOBADASER (Spain), SCQM (Switzerland), and BSRBR-AS (UK, only for axSpA).
Those not included are Turkey, Crete, Sweden, Germany, Poland and the Netherlands. Several of these were not part of EuroSpA when the study began.
