How Ankylosing Spondylitis Is Different For Women

In the past, doctors thought that ankylosing spondylitis (AS) and axial spondyloarthritis (AxSpA) were more common in men than women. Now, there is a growing understanding that women and men develop AS in equal numbers. The difference is that women take much longer to get a correct diagnosis and tend to be undertreated after diagnosis.1-2

The reasons why it takes women longer to be diagnosed are complicated.

Getting the wrong diagnosis first

The average age when AS or AxSpA symptoms appear is the same in both sexes: between 24 and 28 years old. However, studies show it takes women 2 to 8 years longer than men to get a correct diagnosis. The most common incorrect diagnoses made are:1-3

Doctors believe there are several reasons for this. First, ankylosing spondylitis and AxSpA can be just as severe in women as in men. However, men tend to have more inflammation and joint damage that doctors can spot easily on x-ray.1-3

Doctor bias also plays a role. Women in pain are more likely to be told their pain is due to stress, anxiety, or depression. Thus, women are more likely to be prescribed sedatives rather than pain medicine, or less pain medicine than men.4

AS and axSpa symptoms in women

The first symptoms of AS and AxSpA can be different in women. In women, AS often affects the neck and joints in the arms and legs first. This compares to men who are first affected in the low back, hips, and spine first. Women also often report feeling pain all over their body.

Women with widespread pain are more twice as likely to experience a delay in diagnosis. Men tend to report back pain first, which is a classic symptom.
Over time, fewer women develop fusion of the spine, but have more
problems with daily living.1 Studies report that women tend to feel more pain, more fatigue, and need more drug therapy. Women also feel morning stiffness for longer than men.2

More secondary health conditions

Women with AS and AxSpA are also more likely to have other conditions caused by inflammation, including: 2,3,5

  • Uveitis (eye inflammation)
  • Psoriasis (severe skin rashes)
  • Joint inflammation (enthesitis)
  • Inflammatory bowel disease, Crohn’s disease, or ulcerative colitis (IBD)

One study found that nearly half of women with AS and AxSpA also had uveitis while only one-third of men did. While IBD was less common overall, twice as many women also had IBD compared to men.5

AS medicines in women

Biologics, or tumor necrosis factor inhibitors (TNFi), work less well in women compared to men. Biologics are often used in people with AS who show joint damage on x-ray (radiographic axial spondyloarthritis). Women also switched treatments more and were less likely to stick with TNFi treatment. Doctors believe that women may respond less well to TNFis because they have more body fat.2

Pregnancy with AS or AxSpA

AS and AxSpA often begin in the mid-20s, a time when many women want to have children. AS and AxSpA can complicate pregnancy, making back pain worse from week 20 through the third trimester. Some studies show that pregnant women feel fewer symptoms during pregnancy while others feel more. It may be that women who take biologics (TNFis) before pregnancy and stop taking their medicine will flare during pregnancy.

Women who flare during pregnancy also have more problems with gestational diabetes, preeclampsia, infection, preterm labor, and low birth weight babies. Women diagnosed with AxSpA are more likely to choose a cesarean section even though most can deliver vaginally.1

The same treatments for AS and axSpa are recommended for both men and women, except during pregnancy. NSAIDs are not recommended during pregnancy, especially in the third trimester. Methotrexate and leflunomide are known to cause birth defects and should not be taken while pregnant or breastfeeding. TNFis are generally safe until 20 weeks. After that, only certolizumab is safe in later pregnancy. TNFis seem to be safe to take while breastfeeding.1

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