by Dr. David Borenstein, Medically Reviewed by Dr. C.H. Weaver M.D. Updated 4/2022
Ankylosing spondylitis (AS) is an inflammatory spinal disease which is associated with varying degrees of spinal fusion. In the past, AS was thought to be primarily a disease of men. However, it has become clear that men and women develop AS. Sexual differences do exist in the expression of the illness in regard to severity of disease and response to therapy.
A number of myths have been identified in a paper reviewing the differences that sex makes with AS.1
First, men and women with AS are physiologically the same. Testosterone decreases the pro-inflammatory tumor necrosis factor (TNF) while boosting the production of anti-inflammatory Il-10. Estrogens promote pro-inflammatory TNF, Il-1 and Il-6. Women have a greater number of pain receptors, higher pain sensitivity, and higher pain scores. Women may have a higher amount of body fat that may act as an inflammatory tissue.
A second myth is that AS is a predominately male disease. Initially, the ratio of men to women with AS was thought to be 10 to 1. More recent studies with better radiographic techniques have shown ratios close to 1 to 1 for AS and non-radiograph spondyloarthritis. Another difference is the time to diagnosis. Since women were not thought to have the AS diagnosis, generalized pain in women was thought to be fibromyalgia. The average is 10 years in women and 7 years in men. Another complication is the confusion with the sacroiliac changes associated with pregnancy that may be confused with AS.
A third myth is the perception of worse disease outcome with men versus women. Women have increased level of extra-articular disorders like eye inflammation, uveitis. They may also have an increased risk of inflammatory bowel disease.
A fourth myth is no sex differences are present in efficacy and drug survival of biologics in AS. In general, women have a significantly lower efficacy, response rate, and drug survival of TNFs compared to men.
Sex does make a difference when it comes to AS. Women do get AS. Assuming what happens in men also happens in women is not correct. Women are different, to state the obvious, in lots of different ways. That includes AS.
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- Rusman T et al. Sex and gender differences in axial spondyloarthritis: myths and truths. Rheumatology 2020:59:iv39-iv46