AS causes inflammation of the ligaments and joints of the spine, which leads to its early symptoms. It might cause inflammation of the sacroiliac (SI) joints that link the pelvis to the spine. AS can also affect the peripheral joints of the arms and legs, such as the knees, hips, and elbows.
This article will cover the typical age of onset for ankylosing spondylitis, early warning signs, and early treatment.
Typical Age of Onset
Ankylosing spondylitis onset usually peaks in your 20s and 30s, according to a 2022 Rheumatology report. That same article reported the average age of onset worldwide was 26.
According to Johns Hopkins Medicine, around 80% of people with AS will experience symptoms before age 30. Around 5% have a symptom onset after age 45. Onset after age 50 is extremely rare.
Sex Differences in AS Onset
It was once believed that AS primarily affected people assigned male at birth. But newer studies suggest the male-to-female prevalence ratio is around 1.03-to-1.
Diagnosis of AS is often delayed in people assigned female at birth. Factors that might lead to a delayed diagnosis are bias and differences in symptom presentation, disease progression, and radiographic changes (those seen on X-ray imaging).
Ankylosing spondylitis is a severe subset of axial spondylitis. Many people with AS are initially diagnosed with non-radiographic axial spondylitis (nr-axSpA), the second, less aggressive subset of axial spondylitis. Nr-AxSpA is characterized by spinal and SI joint inflammation without radiological changes.
Nr-axSpA is sometimes a precursor to AS, with people assigned female at birth more likely to be diagnosed with it. Once damage to the SI joints and the spine can be seen on X-rays, the disease has already progressed. Not everyone with nr-axSpA will go on to develop AS, and for those who do, the progression will slow.
(Note that Verywell Health prefers to use inclusive terminology, but when reporting research findings or quoting authoritative sources, the terms referring to the sex or gender in the sources will be used.)
Early Warning Signs
The earliest symptoms of AS are pain and stiffness in the low back and hips. These symptoms tend to present more often in the morning and after the person has been inactive. They may also feel pain in the neck. Fatigue is another symptom of early AS.
Early on, symptoms appear slowly and get worse over time. People with AS might experience flare-ups—times in which AS symptoms worsen—and periods of remission, with few or no symptoms.
Additional early signs of AS are:
Buttock and hip painPain, swelling, tenderness, warmth, and redness of the peripheral jointsBack pain that wakes you up at night Back pain that lasts 30 or more minutes after waking upAppetite lossMild fever
Pain and stiffness in AS can improve with movement and activity.
Typical Rate of Progression
Disease progression takes many years or even decades to occur. Early aggressive treatment with medication and healthy lifestyle habits might slow the progression and stop the damage AS is known to cause.
Nearly 25% of people with AS experienced disease progression over time, according to the results of a 2019 study. Factors that play a part include male sex, presence of joint damage at the time of diagnosis, an active disease state, and higher inflammatory markers predictive of spinal damage.
The study’s researchers also found that treatment with tumor necrosis factor (TNF) inhibitors could slow the progression rate.
Another indicator of disease progression in AS is genetics and family history. Research shows disease severity and functional impairment are consistent in families. This means if one family member has a more severe disease, other family members are likely to have similar disease outcomes.
Disease severity and progression are also linked to a genetic marker called HLA-B27. This marker is also linked to a worsening prognosis and tends to occur in families. How HLA-B27 is inherited is not clearly understood, and HLA-B27 is not always passed on.
In addition to spine and SI joint changes, AS will cause inflammation of the entheses (the areas where ligaments and tendons meet bone), which means scar tissue and extra bone growth in the spine.
Over time, these changes cause limited spine mobility, curvature, and spinal fractures. Other joints, including the hips and shoulders, might also be affected by AS joint damage.
Early Treatment
Early diagnosis and treatment are vital to preventing the future progression of AS. A wide range of treatments is available for managing AS. These treatments can slow down disease progression and reduce symptoms and pain.
Treatments for AS include:
Medicines to reduce inflammation and relieve pain, including nonsteroidal anti-inflammatory drugs (NSAIDs), biologics that work on the immune system, and corticosteroids to quickly bring down inflammation Physical therapy to strengthen the back and neck and help relieve pain Exercises to manage posture and joint flexibility Surgery to restore function in AS-damaged joints, but most people with AS will never need surgery
These therapies can reduce the signs and symptoms of AS caused by chronic inflammation. Bringing down inflammation might reduce progression and prevent joint damage and loss of mobility.
Summary
Ankylosing spondylitis causes chronic inflammation of the spine. It sometimes starts as non-radiographic axial spondyloarthritis, where inflammation is present, and no joint damage is visible on an X-ray.
AS typically starts in the second and third decades of life. Progression occurs over many years, and AS will worsen with age. Treatment with medications, physical therapy, and exercise can reduce inflammation and slow down disease progression. While rare, some people with AS will require surgery to restore the function of the spine.
A Word From Verywell
A fused spine and severe spinal curvature might occur in the late stages of ankylosing spondylitis. Fortunately, for most people, the condition never progresses that far. Following your prescribed treatment plan is essential to slow down the progression and improve your prognosis.
If you have persistent symptoms in your spine or are concerned about progressive damage to your spine, let your healthcare provider know. A growing number of medicines are available to manage symptoms effectively. These different options can delay or prevent disease progression.
