What is the background to this research?
Axial spondyloarthritis (axSpA) is a long-term inflammatory condition that mainly affects the spine and joints in the pelvis, causing pain, stiffness, and fatigue. To decide how active someone’s condition is, and whether certain treatments like biologic medicines are suitable, doctors use different tools that measure how active the disease is in individual people.
Some of these tools rely on how patients feel (for example, how bad their pain or fatigue is), while others use blood tests that show levels of inflammation. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS) are two common measures.
However, many people with axSpA also live with other health conditions—such as heart disease, diabetes, depression, or lung problems—which could influence how they rate their symptoms or how doctors interpret their test results. This study aimed to understand whether these other conditions (“comorbidities”) may make disease activity appear worse, even where more ‘objective’ measures such as inflammation from axSpA itself aren’t actually higher.
What did we seek to find out?
The researchers wanted to know:
- Whether having other health conditions affects how active axSpA appears to be, depending on which disease activity measure is used.
- Whether comorbidities influence related outcomes like fatigue, physical function, and quality of life.
- Whether a key part of the ASDAS—the “patient global” question (asking how active their spondylitis has felt recently)—is influenced by other health problems.
What did we do?
This study used information from the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis (BSRBR-AS), which has followed people across the UK who either were or were not starting biologic therapy for axSpA.
Researchers looked at data from 2,043 people who had filled out an initial baseline questionnaires and provided medical information. Participants reported symptoms such as pain, stiffness, and fatigue, and clinicians recorded whether they had other diagnosed conditions like heart disease, depression, or asthma.
The researchers then compared disease activity scores, inflammation markers, fatigue, and quality of life between people with and without these other health conditions, taking into account factors such as age, gender, weight, smoking, and education.
What did we find?
- About half of participants had at least one other long-term health condition besides axSpA.
- People with additional health conditions were generally older and had slightly higher body weight.
- Patient-reported scores such as BASDAI and spinal pain were higher in people with more comorbidities.
- However, inflammation blood tests (CRP and ESR) did not differ between people with or without comorbidities.
- The ASDAS score, which combines patient answers with blood test results, was only slightly affected by comorbidities—and the differences were not large enough to be clinically meaningful.
- Certain health conditions—especially depression, heart failure, and peptic ulcer disease—were linked to worse reported pain, fatigue, and quality of life.
- Overall, measures that rely mainly on patients’ perceptions (like BASDAI) were more strongly influenced by comorbidities than mixed measures like ASDAS.
Why does this research matter?
This study shows that the way we measure axSpA activity can be affected by other health problems that patients have. In routine care, this means doctors should be cautious when interpreting high BASDAI or pain scores in people who also have conditions such as depression or heart disease, as these may inflate scores even if inflammation is stable.
The ASDAS appears to be a more reliable tool when people have multiple health conditions, as it is less influenced by unrelated symptoms or general ill-health. This finding supports the use of ASDAS for assessing disease activity and making treatment decisions, especially for people with several comorbidities.
Future research will look at whether having other health problems affects how people respond to treatments over time.
Who funded this study?
The study was funded by the British Society for Rheumatology as part of the BSRBR-AS registry programme.
Where can I read more?
You can read the full research paper here.