Axial spondyloarthritis (axSpA) is a chronic inflammatory disease that primarily affects the spine and sacroiliac joints.1 The most common symptoms include chronic low back pain, stiffness and fatigue, which are especially more intense in the morning and improves with movement.2,3 In this sense, defining and measuring the disease activity experienced by patients is essential and challenging.

In this context, the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) has traditionally been the most widely used scale in clinical practice to assess disease activity,4 to guide medical therapy and monitor treatment response to improve the quality of axSpA care.5 However, the recommended instrument to assess disease activity nowadays is the Ankylosing Spondylitis Disease Activity Score (ASDAS), which in addition to patient-reported questionnaire also includes an objective assessment of inflammation such as C-reactive protein or erythrosedimentation rate.6

Disease activity can be heterogeneous, both at initial presentation and over time.7,8 Although some studies have shown that – even in countries with wide access to biologics – axSpA remains a disease in which more than one third of patients could remain with moderate to high disease activity for several years.9

Some individual characteristics are strongly associated with stable trajectories of low and improving disease activity, such as being male or having a higher degree of education.9 Females also experience higher disease activity reported by BASDAI scale,10,11 although variation depends on the geographic location of the patients.12 However, when using the ASDAS, the influence of gender was not found.13

Some studies have demonstrated an association between elevated disease activity and progression of structural damage in the spine in patients with axSpA.14,15 Therefore, disease inactivity would also result in controlling of radiographic progression of the spine in axSpA.16 AxSpA is a chronic condition that may require long-term management by a specialized medical team, which should include rheumatologists, physiotherapists and other healthcare professionals to provide comprehensive treatment and improve the patient's quality of life. Hence, for an adequate management of patients it is crucial to assess the patients’ disease activity and what factors might be associated with such activity. We aimed to assess the prevalence of clinically active disease in axSpA and its associated factors in a large sample of patients from the International Map of Axial Spondyloarthritis (IMAS).

Of 5295 patients, mean BASDAI was 5.4 (SD 2.1) with 75% having active disease (BASDAI ≥4). Specifically, 96.2% of patients reported axial affection with a mean of 5.7 out of 10, while 88.8% reported peripheral affection with a mean of 4.6 out of 10 (Table 2).

In South Africa, 87.0% of patients reported having active disease, compared to 68.5% in Asia (Fig. 2). Patients with active disease were frequently younger, females, with less physical activity, with greater number of self-reported symptomatic body regions, greater spinal stiffness, higher functional limitation, longer diagnostic delay, higher prevalence of inflammatory bowel disease, greater work choice due to axSpA, higher difficulty finding a job due to axSpA, poorer mental health and greater use of csDMARDs (Table 3). Bivariate analyses between independent variables and active disease for each region are available in Supplementary Table 1.

Fig. 2.

Mean of disease activity and proportion of active disease by region (n=5295). Data shown in the circles refer to the mean of disease activity (% active disease, BASDAI ≥4). BASDAI: Bath Ankylosing Spondylitis Disease Activity Index.

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There was a significant interaction between gender and age (OR=0.98, p<0.001), physical activity (OR=0.77, p<0.001), spinal stiffness (OR=1.19, p<0.001), functional limitation (OR=1.01, p<0.001), diagnostic delay (OR=0.99, p=0.031), presence of inflammatory bowel disease (OR=1.33, p=0.005), difficulty finding a job due to axSpA (OR=1.60, p<0.001) and mental health GHQ-12 scores (OR=1.11, p<0.001). Therefore, we performed an additional regression analysis stratified by gender to assess factors associated with active disease showing in both genders an association between active disease and higher functional limitation, greater spinal stiffness, difficulty finding a job due to axSpA and worse mental health. In addition, only for males, younger age and shorter diagnostic delay, and only for females, no physical activity and presence of inflammatory bowel disease were associated with active disease (Table 4).

The present study assessed the disease activity of 5295 axSpA patients from 27 countries around the globe and found a mean disease activity of 5.4 and active disease in 75% of the patients. Active disease was more likely at a younger age, female gender, a higher number of self-reported symptomatic body regions, greater spinal stiffness, higher functional limitation, shorter diagnostic delay, presence of inflammatory bowel disease, difficulty finding a job due to axSpA, work choice due to axSpA and poorer mental health. In the multivariable linear regression stratifying by gender, higher functional limitation, greater spinal stiffness, difficulty finding a job due to axSpA (with greater weights in males) and worse mental health were associated with active disease in both genders. However, only for males, younger age and shorter diagnostic delay, and only for females, no physical activity and the presence of inflammatory bowel disease were associated with active disease.

The mean disease activity of IMAS patients (5.4) was one point higher than a recent study (4.5) that also included patients from different regions of the world such as Europe, China, Latin America, Canada and Arab countries, although in both studies the proportion of patients with high disease activity was lower in Asia.12 This could be to the fact that the Asian patients in the IMAS cohort reported a shortest delay in diagnosis and, therefore, were able to initiate effective treatment earlier to reduce disease activity. In addition, almost 9 out of 10 patients in IMAS South Africa had an active disease. This may be due to the fact that the South African patients in the IMAS cohort waited more than 10 years before diagnosis which, in addition to being unacceptable, could severely restrict the quality of life of these patients.

Active disease was higher in female IMAS patients. This could be due to the fact that female patients experience a longer diagnostic delay, greater functional limitations – although they have less structural damage to the spine – as well as a lower trend of adherence to treatment and a poorer response to treatment.22

Patients with active disease in IMAS cohort experienced significant disease burden in terms of symptomatic body regions and spinal stiffness and functional limitations for both genders and diagnostic delay for males. Functional limitation of IMAS patients was also associated with severe pain, as measured by BASDAI items Q2 and Q3.23 Disease activity may damage the sacroiliac joint, influencing the functional status and mobility of the spine.24 In addition, high disease activity is associated with accelerated radiographic progression of the spine especially in early axSpA.25

With respect to extra-musculoskeletal manifestations, IMAS patients with active disease were associated with the presence of inflammatory bowel disease, although stratifying by gender, this was only significant in the case of females. This may be due to the higher prevalence of inflammatory bowel disease among women with AxSpA.26

Higher disease activity can disrupt the working life of patients with axSpA, with greater weight of difficulty in finding a job due to axSpA for males. In addition, difficulty finding a job due to axSpA was associated with pain severity, assessed by BASDAI items Q2 and Q3, in IMAS patients.23 This could be due to the existence of a higher proportion of males who tend to perform manual labor, which requires greater physical effort.27 We found higher disease activity was associated with job loss,28 greater work impairment,29 absenteeism,30 and decreased work productivity.31 In this sense, the most frequent work-related issues in patients with axSpA were sick leave, difficulty fulfilling working hours and missing work for doctor's appointments. In addition, a higher number of work-related issues was associated with higher disease activity.32 As it emerges, disease activity in patients with axSpA should not only be considered with respect to the disease burden, but also to the impact on patients’ quality of life, especially the working life, as these patients are much more restricted than the general population.

IMAS axSpA patients with higher disease activity suffered poorer mental health for both genders although with a slight greater impact on females. In this context, higher disease activity was associated with moderate–severe depressive symptom,33 risk of anxiety,34 and risk of mental disorders.35 Moreover, a strong association between higher disease activity and poorer mental health was found.36 Although more attention is currently being paid to the mental health of axSpA patients, their psychological status should be closely examined, especially in view of the significant effect on disease burden and disease activity.

In the IMAS cohort, the use of NSAIDs and bDMARDs was not significantly associated with active disease, which may indicate that these treatments may have the disease under control. Previous studies have shown that treatments such as NSAIDs and bDMARDs are targeted to reduce inflammation and progression of disease activity.37,38 It should be noted that non-pharmacological treatments are also beneficial in reducing disease activity and improving patients’ quality of life.39 Thus, optimal treatment of axSpA should include a combination of pharmacological and non-pharmacological treatments.

Assessment of disease activity plays an essential role in management decisions of axSpA due to its wide association of symptoms across body regions, spinal stiffness, functional limitation, working impact and mental health. Disease activity should be measured by validated tools such as the BASDAI scale or ASDAS (Ankylosing Spondylitis Disease Activity Score) which has demonstrated better psychometric properties,40 despite which, many healthcare professionals continue to use the BASDAI scale to measure patients’ disease activity.

High disease activity according to BASDAI may not be due to inflammatory activity, but to other issues, such as non-nociceptive pain mechanisms (non-disciplastic, neuropathic), structural damage, mechanical/degenerative problems in the spine. Therefore, it is essential that axSpA patients communicate effectively with their physicians to describe their symptoms. Based on this evidence, the healthcare professional can adjust the treatment regimen to control disease activity, reduce symptoms and improve the patient's quality of life. Treatments should include non-pharmacologic therapy, work-related guidance, anti-inflammatory drugs, and in case of failure of these, biologics, or specific targeted therapies to control inflammation.

IMAS is an international survey of axSpA patients, including 5557 respondents from 27 countries worldwide, making it the largest sample and coverage to date. This study includes an important number of factors associated with disease activity, the identification of which may aid improvements in the management and follow-up of axSpA patients by rheumatologists and other HCPs. However, IMAS has some limitations. First, the survey was based on self-reported data and was unable to confirm the patients’ diagnosis. Secondly, information on the symptomatic body regions and extra-musculoskeletal manifestations were self-reported by patients. Furthermore, there is an overrepresentation of the European region compared to other regions such as Asia or South Africa. Finally, the lack of comparison of the BASDAI with other scales with better psychometric properties such as the ASDAS is another limitation of the study.

Worldwide, 75% patients with axSpA reported clinically active disease according to BASDAI, with higher proportion of patients with active disease in South Africa and lower proportion in Asia. The causal relationship between the identified factors and clinical disease activity is complex and may vary from patient to patient, although a significant association has been found with respect to symptomatic body regions, spinal stiffness, and functional limitation of patients. In addition, disease activity may be affecting patients’ mental health and employment status. Regarding the assessment of active disease, significant interactions were found between female gender and age, number of self-reported symptomatic body regions, spinal stiffness, functional limitation, inflammatory bowel disease, difficulty finding a job due to axSpA, and mental health GHQ-12 scores. Our results underline the complexity of the clinical disease activity concept in axSpA and the need for a holistic approach in the patient management, care, and treatment.

All authors had full access to all study data, participated in the drafting and revision of the article, and approved the final version to be published.

This article does not contain any studies with animal subjects. All participants were asked to provide explicit opt-in consent prior to participating in the EMAS survey.

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Participant data was anonymized.

This study was supported by Novartis.

Marco Garrido-Cumbrera Grant/research support from: Novartis, Denis Poddubnyy Speakers bureau: AbbVie, BMS, Celgene, Janssen, Lilly, MSD, Novartis, Pfizer, Roche and UCB, Grant/research support from: AbbVie, MSD, Novartis, and Pfizer, Fernando Sommerfleck Speakers bureau: Abbvie, Eli Lilly, Janssen, Novartis, Consultant of: Abbvie, Novartis, Janssen, Christine Bundy Speakers bureau: AbbVie, Celgene, Janssen, Lilly, Novartis and Pfizer, Souzi Makri Consultant of: ovartis, GSK and Bayer, Shashank Akerkar Speakers bureau: Pfizer, Novartis, Eli Lilly, Jansen, Jo Lowe Grant/research support from: No personal funding, but ASIF has received funding from Novartis, UCB, Lilly, Abbvie, Boehringer Ingleheim, Pfizer, Janssen, Elie Karam: None declared, José Correa-Fernández: None declared, Victoria Navarro-Compán Speakers bureau: AbbVie, Eli Lilly, Janssen, MSD, Novartis, Pfizer, UCB Pharma, Consultant of: AbbVie, Eli Lilly, Galapagos, MoonLake, MSD, Novartis, Pfizer, UCB Pharma, Grant/research support from: AbbVie, Novartis.