Here are some key facts about ankylosing spondylitis and women.
1. Ankylosing spondylitis isn’t just a “man’s disease.”
Contrary to historic misconceptions about ankylosing spondylitis, the condition doesn’t predominantly affect men. While the earliest studies of the disease put the incidence rate in men compared with women at about 10 to 1, more recent research shows that the rates are closer to equal for men and women, according to the Spondylitis Association of America (SAA). “It’s practically the same now,” says Susan Goodman, MD, a rheumatologist at Hospital for Special Surgery and professor of clinical medicine at Weill Cornell Medical College, both in New York City. This new understanding has to do with changes in how ankylosing spondylitis is defined and diagnosed. Starting in the 1980s, doctors began using magnetic resonance imaging (MRI) to see active inflammation in the sacroiliac (SI) joints, which connect the bottom of the spine to the pelvis, giving them the ability to see damage that may not be visible on X-rays. This made it possible to diagnose ankylosing spondylitis earlier. In 2009, doctors began using the umbrella term axial spondyloarthritis (axSpA) to refer to inflammatory arthritis that causes pain and swelling primarily in the spine and SI joints. There are two subtypes of axSpA:
Nonradiographic axSpA (nr-axSpA), which means joint damage is not visible in X-raysAnkylosing spondylitis (or radiographic axSpA), which means joint damage can be seen in X-rays
These two categories can be thought of as two stages of axSpA: one with little or no damage in the spine or SI joints and one with definite, clearly visible damage. (It should be noted that not everyone with nr-axSpA goes on to develop changes that can be seen on X-rays, notes Joerg Ermann, MD, a rheumatologist at Brigham and Women’s Hospital in Boston.) This new way of defining axSpA made it possible for the condition to be more visible in women, who tend to have fewer changes, or damage, that can be seen in X-rays, according to Dr. Goodman. “Women are less likely to have radiographic damage, so if your screening procedure is an X-ray, you’re less likely to be able to confirm a diagnosis in a woman,” says Goodman. “MRIs have really changed that, and now we’ve seen more of a gender parity.”
2. It takes longer for women to get the correct diagnosis.
Women experience a significant delay in receiving an ankylosing spondylitis diagnosis compared with men, according to the SAA. A review published in August 2020 in Seminars in Arthritis and Rheumatism found that it can take about 9 years on average, versus 6.5 years for men, for women to get the right diagnosis. This can delay appropriate treatment. One factor is a persistent misunderstanding of how prevalent ankylosing spondylitis is in women. “I think the biggest factor is probably bias on the part of healthcare providers,” notes Dr. Ermann. “If you don’t fit the demographics, you’re less likely to get the diagnosis.” Differences in how ankylosing spondylitis affects women may also lead to misdiagnosis. Women tend to experience pain in areas that aren’t considered typical of ankylosing spondylitis — the joints of the arms, legs, or neck, for instance. “Because of this, women are more likely to get an initial diagnosis of fibromyalgia,” says Ermann. “And that also may have something to do with bias, because fibromyalgia is more common in women than in men and is considered to be a female disease.” Results of a survey of 235 people with ankylosing spondylitis published in June 2019 in the journal Rheumatology and Therapy found that 21 percent of women were incorrectly diagnosed with fibromyalgia compared with 7 percent of men. Ankylosing spondylitis is also often wrongly diagnosed as chronic back pain caused by minor trauma, bad posture, or poor body mechanics, says Goodman. “If you look at what a general practitioner deals with, 90 percent of women at some point or another go in complaining of lower back pain,” says Goodman. “So to be able to sort out inflammatory back pain is a bit of a challenge.” Most doctors don’t routinely screen for inflammatory arthritis since lower back pain is so common. “I think that combination — normal X-ray, no consistent screening for inflammatory back pain, and I personally think that there is a tendency to disregard women’s musculoskeletal complaints — has been a real problem over time,” says Goodman.
3. Women have less radiographic damage but more disability.
As noted, women tend to have less joint damage that can be seen on an X-ray than men, according to the SAA. Doctors have theories — but no clear explanation — for this distinction. “This may be linked to sex differences in how men and women react to inflammation in ankylosing spondylitis or how they respond to medications used to treat the condition,” says Ana-Maria Orbai, MD, an assistant professor of medicine and the director of the psoriatic arthritis program in the division of rheumatology at Johns Hopkins Medicine in Baltimore. Gene selection may also play a role, according to Ermann. The type of damage that is spotted on X-rays also creates problems for people who are pregnant or plan to become pregnant. “So maybe, because of that, there was a natural selection of genes that control radiographic progression in women.” Smoking is another potential factor for radiographic progression, and “historically, it was more common for men to smoke than women,” says Ermann. Though women have less radiographic damage, they tend to experience more symptoms, such as increased fatigue, pain, and limitations in mobility, notes the SAA. “If you look at the scores that are used to measure disease activity, [women] often have higher scores than men,” says Ermann. “And when you use tools that measure quality of life, women fare worse than men.” This remains true even when you control for disease activity in some objective way, which means women are somehow experiencing the disease differently, he adds.
4. Women tend to have more widespread pain.
Women with axSpA tend to have more inflammation and pain in areas beyond the back, such as in the joints of the neck, arms, and legs, and are less likely to see a doctor specifically for back pain, according to a review published in 2018. In contrast, men are more likely to primarily experience lower back pain, which is a more commonly recognized symptom of ankylosing spondylitis. “Pain characteristics in women are less typical,” says Ermann. “Women have more pain in the upper neck, and it’s more widespread.” And women with widespread pain experience a significantly longer delay in diagnosis, according to the SAA.
5. Some research suggests women may have an increased risk of associated conditions.
Some research has pointed to possible sex differences in conditions related to ankylosing spondylitis. A review of 734 people with ankylosing spondylitis in Ireland presented at the 2019 annual meeting of the American College of Rheumatology found that women may have higher rates of inflammatory bowel disease and uveitis. Other studies have shown that psoriasis may occur more frequently in women compared with men, according to the 2018 review. However, according to Ermann, more data is needed before firm conclusions can be drawn about whether these conditions are more common in women than men.
6. Pregnancy and childbirth will require discussions with your doctor and monitoring your symptoms.
Because ankylosing spondylitis is typically diagnosed in people younger than 40 (with as many as 80 percent of people developing their first symptoms before age 30, according to research published in July 2022 in StatPearls), pregnancy and childbirth is an issue many women will want to discuss with their doctors. There hasn’t been enough research on pregnancy and ankylosing spondylitis, likely because the disease was previously considered to be a male disease, says Ermann. And the fact that many women have lower back pain during pregnancy can make it difficult to sort out who may be experiencing symptoms of ankylosing spondylitis, notes Goodman. Some studies suggest that, in general, having a baby will not significantly change the course of your disease, according to the Arthritis Foundation. However, there’s some data to suggest there’s an increased risk of pregnancy complications and higher rates of C-sections in women who have ankylosing spondylitis, especially if disease activity is high, says Ermann. Research shows that symptoms may worsen during the second and third trimesters of pregnancy, possibly due to women stopping their medications or the physical demands of pregnancy on the body, according to the SAA. In a study of women with axSpA, researchers found that disease activity and pain were highest during the second trimester. And, according to the SAA, when disease activity increases in pregnancy, women are more likely to experience complications such as gestational diabetes, preeclampsia, infection, and preterm labor and delivery. Women with axSpA are also more likely to have elective C-sections and give birth to babies who are small for their gestational age, according to the SAA. “If the sacroiliac joints are fused, it can be very hard for labor and delivery,” says Goodman. “But in most cases, this really isn’t a problem, because one of the things that happens around the time of delivery is you release a lot of hormones that relax the pelvic ligaments and structure.” Not only that, she notes, but young women of childbearing age are also unlikely to have had the disease for a long time or developed fusion of the SI joints. After the baby is born, studies suggest that ankylosing spondylitis symptoms can worsen in new moms, but it’s not clear if this is due to lifestyle changes, such as not being able to get enough sleep or exercise or experiencing more stress, according to the SAA. As for ankylosing spondylitis treatment during pregnancy, doctors don’t recommend nonsteroidal anti-inflammatory drugs (NSAIDs) — typically a first-line medication— for women in their third trimester, says Ermann. Of the biologics doctors use to treat ankylosing spondylitis, tumor necrosis factor (TNF) inhibitors are generally considered safe in pregnancy, but there isn’t enough information yet on interleukin 17 inhibitors in expectant mothers, says Ermann. If you’re pregnant or planning to become pregnant, talk to your doctor about how you may need to adjust your ankylosing spondylitis treatment plan.
7. Ankylosing spondylitis can affect your emotional health.
People with ankylosing spondylitis are more likely to experience depression and anxiety than those who don’t have the disease, according to an analysis of data from previously published studies published in March 2020 by the journal BMC Rheumatology. The authors of the BMC Rheumatology analysis noted that their finding highlights the importance of evaluating and treating the mental health of people living with the condition. “This would apply to both men and women,” Ermann notes. While symptoms such as pain and physiological limitations may affect both men and women, says Dr. Orbai, the condition may be more likely to trigger feelings of guilt in women. “Ankylosing spondylitis causes stiffness and pain as well as fatigue,” says Orbai. “Women may feel guilty when they are not able to function at the level they expect from themselves, which in turn may lead to anxiety and depression and other forms of emotional impact.”
8. More research is needed on treatment for women.
TNF inhibitors, which are a type of biologic medication used to treat ankylosing spondylitis, seem to be less effective in women, and some studies show that women tend to switch medications more frequently, which may indicate that they aren’t working for them. Doctors aren’t sure why these medications may be less effective in women — one theory suggests women’s higher body fat may play a role — but given that the majority of research has been done in men, it’s clear that more studies need to be done on the treatment of ankylosing spondylitis in women specifically.
