Ankylosing spondylitis (AS) causes inflammation in the joints of the spine, lower back, and pelvis. Females may also be more likely to have pain in the neck, knees, and ankles, as well as systemic symptoms, such as bowel inflammation.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

AS is a type of arthritis. The inflammation that occurs with AS can lead to chronic pain and difficulty with mobility. It affects around 3 million people in the United States.

Historically, experts considered ankylosing spondylitis (AS) to be a health issue that mainly affected males. More recent research indicates that it is nearly as prevalent in females and that its severity has nothing to do with a person’s sex.

The belief that AS mainly affects males likely resulted from an underrepresentation of females in related research, according to a review of medical evidence conducted in 2018.

The team behind the review also found that females with AS have a higher disease burden than males — due to longer delays in diagnosis, high levels of disease activity, and less responsiveness to treatments that target tumor necrosis factor (TNF).

TNF is a protein in the body linked with inflammatory conditions such as arthritis. A few examples of medications that act on TNF include etanercept (Enbrel) and adalimumab (Humira).

This article looks into the prevalence and symptoms of AS in females, as well as other aspects of the disease.

The hands and back of a woman with ankylosing spondylitis.Share on Pinterest
Edwin Remsberg/Getty Images

AS can affect anyone. As the Spondylitis Association of America points out, the disease and its severity have nothing to do with a person’s sex.

Estimates of the prevalence of AS vary. The 2018 review found that, historically, the prevalence of AS in males to females was 10 to 1 but that the most recent study found a ratio of 1.03 to 1.

Symptoms of AS vary from person to person. Some common early symptoms include:

The Spondylitis Association of America observes that the symptoms of AS can present differently in females, compared with males. For example, a female with AS may first have pain in the neck, or elsewhere, rather than the lower back.

As AS progresses, the symptoms may change and include:

  • pain on both sides of the body
  • stiffness and pain in the neck, ribs, shoulder blades, hips, and heels
  • increased fatigue
  • mild to moderate anemia

Do females have the pain in different places?

AS affects the same joints, regardless of sex. However, females may be more likely to experience pain in the neck, knees, and ankles.

Systemic symptoms related to AS, such as bowel inflammation, may also be more common in females, compared with males.

Experts still debate whether sex is a risk factor for AS.

While many doctors once thought that being male increased the risk of developing AS, some experts and organizations now recognize that a female may have a nearly equal risk of developing the disease.

The healthcare community is still unsure of the exact cause of AS, but genetics may be partially responsible. The Spondylitis Association of America notes that most people with AS have a gene that makes a protein called HLA-B27.

Having this gene does not guarantee that a person will develop AS, however, and some people without the gene still develop the disease.

This leads scientists to believe that other genetic factors and a triggering infection or injury causes people with a risk of AS to develop it.

Risk factors for AS include:

  • the HLA-B27 marker gene
  • an age of 17–45
  • a family history of AS
  • bowel inflammation
  • changes in gut bacteria
  • recurrent gastrointestinal infections
  • inflammatory bowel disease

According to the Arthritis Foundation, having AS does not affect fertility or reproductive health. However, a person with AS who is planning to become pregnant should discuss family planning and care with a rheumatologist.

A rheumatologist and obstetrician can guide a person with AS toward pregnancy-safe treatments. Some treatments for AS, such as methotrexate or nonsteroidal anti-inflammatory drugs (NSAIDs), may be harmful during pregnancy.

AS symptoms may continue throughout a pregnancy, remaining stable or worsening. In some people, the symptoms may lessen.

AS may make vaginal delivery more difficult, due to inflammation in the hip joints. This means that someone with AS may be more likely to need a cesarean delivery. Also, spinal swelling can make it difficult for some people with AS to receive an epidural during the delivery.

Treatment for AS is very similar, regardless of sex. It can consist of:

Doctors may prescribe multiple medications, including:

  • NSAIDs to relieve pain and inflammation
  • corticosteroids to reduce inflammation
  • biologic drugs, such as TNF inhibitors, to treat arthritis in the joints and inflammation in the gut and eyes

While AS treatment is similar for everyone, females may not respond the same way as males to TNF inhibitors, and these drugs may be significantly less effective for females, overall.

Complications of AS can vary in severity and occurrence from person to person. They can develop in anyone with the disease.

AS complications can include:

  • inflammation of the eyes, or uveitis
  • the spinal vertebrae fusing, resulting in stiffness and inflexibility
  • compression fractures
  • reduced lung capacity, due to rib cage immobility
  • cardiac system problems, such as inflammation of the root of the aorta

Additionally, certain side effects may occur more frequently in females than males, including:

  • fatigue
  • pain during the night
  • trouble sleeping or staying asleep
  • a reduced quality of life

Males with AS tend to receive the diagnosis earlier than females.

A large review showed that males with the condition got the diagnosis 2.3 years sooner than females. When the review adjusted for the quality of the reports reviewed, it found that males received the diagnosis 7 months sooner.

The belief among healthcare professionals that AS primarily affects males, combined with publication bias, may be responsible for the delay in diagnosis for females.

The same review found no differences in symptoms of AS that were significant enough to account for the discrepancy in diagnostic timing.

Imaging technology and the standards for diagnosis may also account for some of the delay. Diagnostic criteria for AS include damage to the spinal joints that is visible on X-rays. The Global Healthy Living Foundation reports that males are more likely to have damage that is visible in this way, compared with females.

Anyone who suspects that they may have AS should contact a doctor.

A person with AS should see a doctor regularly and let them know about any new or worsening symptoms.

Also, people who are considering becoming pregnant should consult a doctor first. They can recommend pregnancy-safe AS treatments.

AS is a form of arthritis that causes inflammation in the spinal joints. It can lead to chronic pain and mobility problems.

Doctors once believed that AS primarily affected males. However, recent research shows that females are almost as likely as males to develop the disease.

Due to underrepresentation in research and other factors, it takes longer for doctors to diagnose AS in females, compared with males. Also, symptoms may present differently in females, and certain AS medications may be less effective.