Background/Purpose: The onset of axial spondyloarthritis (axSpA), as defined by the Assessment of SpondyloArthritis International Society (ASAS) criteria is unusual after the age of 45 years. However, axSpA can start after this age with a different phenotype than early-onset forms. The aim of this study was to assess the clinical, biological, and radiological characteristics of axSpA in patients with chronic low back pain at the onset age of older than 45 years.

Methods: A single-center cross-sectional study included patients diagnosed with axSpA between 2018 and 2023. Patients were classified into two groups according to the age of onset of low back pain: late-onset ( > 45 years) and early-onset (≤ 45 years). The clinical, biological, radiological, and therapy data of the two groups were compared. 

Results: A total of 167 patients (104 males, 63 females) were included, clinical characteristics are presented in Table 1. The onset of low back pain after the age of 45 years was observed in 16 patients (9.6%), they showed a shorter duration of disease (6.2±4.9 vs 12.2±9.5 years; p=0.01), a higher prevalence of psoriasis (56.2% vs 10.6%; p< 0.0001), higher scores of BASDAI (7.1±3.5 vs 4.2±2.0 ; p=0.02), ASDAS (4.5±1.2 vs 3.4±1.0; p=0.02) and BASFI (7.9±3.5 vs 4.5±2.5; p=0.01), a lower frequency of radiographic sacroiliitis (62.5% vs 83.2%; p=0.002), a higher prevalence of fibromyalgia (12.5% vs 1.3%; p=0.04) and less use of NSAIDs (64.3% vs 91.2%; p=0.01).  

Table 1: Demographics and disease characteristics of 167 cases of axSpA

No significant differences were found according to sex, family history of spondyloarthritis, inflammatory markers (ESR/CRP), HLA B27 positivity, and the use of TNF inhibitors. Logistic regression analysis confirmed that late-onset low back pain was associated with a shorter duration of disease (OR=0.89, CI 95%: 0.81-0.98), fibromyalgia (OR=0.94, CI 95%: 0.01-0.72), psoriasis (OR=0.1, CI 95%: 0.03-0.28), higher BASDAI (OR=1.5, CI 95%: 1.05-2.22), ASDAS (OR=2.63, CI 95%: 1.12-6.19) and BASFI (OR=1.88, CI 95%: 1.08-3.28) and less use of NSAIDs (OR=5.7, CI 95%: 1.65-19.90).

Conclusion: Our study showed that almost 10% of the patients with axSpA had late-onset chronic low back pain. Moreover, they had a shorter duration of disease, higher frequency of psoriasis and fibromyalgia, higher disease activity, and worse functional severity. Therefore, it is essential to define and validate diagnostic criteria for individuals with onset low back pain after age 45.

« Back to ACR Convergence 2024

ACR Meeting Abstracts - https://acrabstracts.org/abstract/characteristics-of-axial-spondyloarthritis-in-patients-with-onset-chronic-low-back-pain-after-age-45/