Hillary Norton, MD: The epidemiology of axSpA [axial spondyloarthritis] and AS [ankylosing spondylitis] is challenging because these are both underdiagnosed diseases, which makes the epidemiology imperfect. But we do think that the epidemiology for axSpA is 1.7% of the population. And for AS, 0.55% of the population. AxSpA is equivalent between men and women, whereas AS is more common in men.
Symptoms start in the 1920s, which is 1 of the reasons for delay in diagnosis, because generally people who develop back pain in their 20s aren’t aware that this could be a chronic autoinflammatory disease.
This is an invisible disease, and we do know that it’s vastly underdiagnosed. Part of the problem is that when someone develops back pain in their 1920s, they may not go in at all to seek care. When they do, they may go to a chiropractor, a sports medicine physician, or a primary care physician and may not get seen by rheumatology for quite some time. So this leads to the delay in diagnosis.