Just how common is spondyloarthritis globally? Is it more common in certain parts of the world and populations than others? And are we close to being able to estimate the number of people worldwide who have spondyloarthritis?
To investigate these questions, Dutch researchers conducted a literature review, analyzing 30 spondyloarthritis prevalence studies from different parts of the world, spanning nearly four decades (from 1975 to 2014.) “This study is the first to pool global estimated prevalences of spondyloarthritis in the general population and to investigate demographic and methodologic characteristics influencing them,” write the authors in Arthritis Care & Research.
Results: The researchers found that prevalence of spondyloarthritis varied greatly across the world, ranging from 0.20% in South-East Asian populations to a high of 1.61% in Northern Arctic communities. The geographic clustering of spondyloarthritis is likely related to the genetic characteristics of populations, notably HLA-B27 positivity – which is strongly linked to spondyloarthritis.
The researchers also attempted to find specific prevalence numbers for each of the subgroups in spondyloarthritis, but were only able to conduct a meta-analysis for ankylosing spondylitis (AS) and psoriatic arthritis (PsA). The prevalence of AS ranged from a low of 0.02% in Sub-Saharan Africa, to 0.35% in the Northern Arctic. The prevalence of PsA ranged from 0.01% in the Middle East to 0.19% in Europe. The authors reported having too few studies available on other spondyloarthritis subgroups to conduct meta-analyses.
So can we glean a global spondyloarthritis prevalence estimate from these findings? The short answer is “no, not yet.” As we don’t have complete and reliable prevalence numbers for many parts of the world, it is difficult, if not impossible, to estimate with a reasonable level of accuracy just how many people may have spondyloarthritis worldwide.
In fact, it was only in 2012 that the CDC provided the US national prevalence estimates for axial spondyloarthritis, finding that it may affect up to 1% of US adults, or an estimated 2.7 million persons.
“High quality studies are needed to estimate the prevalence of spondyloarthritis in the general population…” say the authors. A reliable world prevalence estimate will only be possible when we have accurate and robust reporting from all regions of the world.
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