What is the background to this research?
Axial spondyloarthritis (axSpA) is a long-term condition that mainly affects the spine and joints in the pelvis, causing pain, stiffness, and fatigue. Many people with axSpA also have other health conditions (called comorbidities) such as depression, high blood pressure, asthma, or diabetes. In fact, more than half of people with axSpA have at least one other health condition.
When these additional conditions are present, they can make assessing the axSpA more difficult. For example, conditions like heart disease or depression can influence how severe someone's symptoms appear to be. This matters because doctors use measures of disease activity to decide whether someone should start or continue taking biologic medicines called TNF inhibitors.
TNF inhibitors are a type of treatment for axSpA that work by blocking inflammation in the body. However, up to half of people do not respond well to their first TNF inhibitor. Understanding whether having other health conditions affects how well these medicines work is important for helping doctors and patients make informed decisions about treatment.
What did we seek to find out?
The researchers wanted to understand how having other health conditions at the time of starting a TNF inhibitor affected how well the treatment worked. They looked at this question in three different ways:
- How much did disease activity scores improve over time in people with and without other health conditions?
- Did people with other health conditions have different chances of achieving specific treatment goals (such as a 50% improvement in their disease activity score)?
- Were people with other health conditions more likely to stop taking their TNF inhibitor?
What did we do?
We studied 994 people with axSpA from the BSRBR-AS register who were starting their first TNF inhibitor. These people came from hospitals across England, Scotland, and Wales. Doctors had recorded whether they had any of 14 different health conditions, including heart disease, lung disease, depression, and diabetes.
We followed people for up to three years after they started treatment, collecting information at regular intervals (at 3, 6, and 12 months, and then annually). We measured their disease activity using questionnaires that asked about pain, stiffness, and how well they could do everyday activities.
We grouped people according to how many other health conditions they had: none, one, two, or three or more. We then used statistical methods to compare how well the TNF inhibitor worked in these different groups, taking into account other factors such as age, gender, body weight, and socioeconomic status.
What did we find?
Who took part? The average age of participants was 45 years, and about two-thirds were men. Before starting treatment, 68% had no other health conditions, 21% had one other condition, and 11% had two or more. The most common other health conditions were depression (15% of people), high blood pressure (11%), and asthma (9%).
Disease activity at the start People with other health conditions had more severe disease at the start of treatment across all measures. Their scores remained higher throughout the study, even though they improved on treatment.
How much did symptoms improve? All groups showed improvement after starting TNF inhibitors, regardless of whether they had other health conditions. For pain and overall disease activity, people with and without other health conditions showed similar amounts of improvement.
However, people with two or more health conditions showed smaller improvements in their ability to do everyday tasks (such as bending down or reaching up) and in their quality of life compared to those without other conditions.
Achieving treatment targets People with multiple health conditions were numerically less likely to achieve common treatment targets at 6 months, though these differences were not statistically significant. For example, people with two or more conditions had about 40% lower odds of achieving low disease activity compared to those with no other conditions.
Stopping treatment The number of people who stopped their TNF inhibitor increased dramatically with more health conditions:
- 29% of those with no other conditions stopped treatment
- 30% of those with one condition stopped treatment
- 42% of those with two conditions stopped treatment
- 68% of those with three or more conditions stopped treatment
People with three or more health conditions were more than twice as likely to stop treatment compared to those with no other conditions.
Why does this research matter?
This research is important because it helps doctors and patients understand what to expect when starting a TNF inhibitor, depending on whether other health conditions are present.
The findings show that having other health conditions doesn't prevent people from benefiting from TNF inhibitors in terms of pain relief. However, people with multiple health conditions may see less improvement in their day-to-day functioning and quality of life, and are much more likely to stop treatment.
This information can help doctors and patients have more realistic conversations about treatment expectations. It also highlights the importance of managing other health conditions alongside axSpA, rather than just focusing on the axSpA alone. Better management of conditions like depression, heart disease, or lung disease might help people stay on their TNF inhibitor treatment and get more benefit from it.
The results also suggest that the current ways of measuring treatment success might not work as well for people with multiple health conditions, and that alternative approaches might be needed.
Who funded this study?
The BSRBR-AS study is funded by the British Society for Rheumatology, which received funding from Pfizer, AbbVie, and UCB (the pharmaceutical companies that make biologic therapies). These companies have no role in deciding what topics to study or how to analyse the data.
Where can I read more?
You can read the full research paper here.