Is Endometriosis a Progressive Disease? What This 2026 Study Actually Shows

By Emanuela Lazzaroni Tealdi, MS Senior Embryologist & Fertility & Reproductive Immunology Specialist

Endometriosis is frequently described as a progressive disease. But what does that actually mean, especially when we look at real surgical data?

A recent study published in Fertility and Sterility examined this exact question using a large surgical cohort and a standardized classification system. The goal was not theoretical, but highly practical: How does endometriosis actually present across different ages in terms of severity and surgical complexity?

Study Overview

This was a retrospective cohort study designed to track disease presentation over time.

• Total Patients: 1,293

• Age Range: 18–51 years

• Diagnosis: All patients had pathology-confirmed endometriosis.

• Procedure: All patients underwent laparoscopic or robotic surgery over a 10-year period.

Patients were stratified into four specific age groups:

• ≤25 years

• 25–35 years

• 35–45 years

• >45 years

The researchers evaluated several clinical factors:

• Disease stage (AAGL classification)

• Surgical complexity (AAGL levels A–D)

• Presence of endometriomas (ovarian cysts)

• Presence of bowel endometriosis

Key Finding #1: Disease Severity Increases Early, Then Plateaus

The prevalence of advanced-stage disease (Stage III–IV) shifted significantly across the age groups:

• 18.3% in patients ≤25

• 44.5% in ages 25–35

• 50.5% in ages 35–45

• 47.0% in >45

Statistically, compared to patients under 25, the adjusted odds (aOR) of having advanced disease were 2.47 for ages 25–35, 2.54 for ages 35–45, and 2.84 for patients over 45.

Interpretation: Disease severity increases with age initially, but it does not continue increasing indefinitely. Instead, it reaches a peak around 25–35 years and then stabilizes. This directly challenges the simplistic idea that endometriosis continuously worsens over time.

Key Finding #2: Surgical Complexity Continues to Increase With Age

While the stage of the disease plateaus, the complexity of the surgery does not.

The prevalence of Level C surgical complexity across age groups was:

• 21.1% (≤25)

• 37.3% (25–35)

• 45.9% (35–45)

• 58.3% (>45)

What this means: Even when the stage appears stable, surgery becomes increasingly complex as patients age. The study explicitly notes that this reflects structural remodeling—such as dense fibrosis, severe adhesions, and anatomical distortion—rather than the continued spread of the disease itself.

Key Finding #3: Endometriomas Follow a Distinct Age Pattern

Endometriomas (endometriosis cysts on the ovaries) demonstrated a unique trajectory. They were:

• Less common in patients ≤25

• More common in patients ages 25–45

• Slightly reduced in patients over 45

Interpretation: Ovarian involvement appears to be a later-developing phenotype. The slight decline after age 45 may reflect hormonal changes, the perimenopausal transition, or surgical selection bias.

Key Finding #4: Bowel Endometriosis Does Not Vary With Age

Interestingly, the study found no significant association between age and bowel involvement.

What this means: Not all severe phenotypes follow the same age-related pattern. Some invasive forms of the disease, like bowel endometriosis, may be entirely independent of age progression.

Key Finding #5: Symptoms Do Not Mirror Severity

The study highlighted a massive disconnect between how a patient feels and what their surgical stage reveals.

• Younger patients had higher rates of dysmenorrhea (painful periods), more non-cyclic pelvic pain, and more gastrointestinal symptoms, despite having generally lower-stage disease.

• Older patients were more likely to have the disease found as an incidental finding and had higher rates of infertility listed as their primary surgical indication.

Critical Point: Symptoms and disease stage are not linearly correlated.

So—Is Endometriosis Progressive?

Based on this study, the answer is yes, but not in a simple linear way. A much more accurate clinical model is:

1. Early Phase: Rapid increase in disease severity and spread.

2. Mid Phase: A plateau in disease stage.

3. Late Phase: Increasing surgical complexity driven by scar tissue and anatomical distortion.

The progression appears to shift from active disease expansion to profound structural remodeling.

Clinical Implications & Limitations

The authors emphasize the absolute necessity of age-specific management, individualized treatment strategies, and the potential value of earlier intervention in selected patients.

• Younger patients face a high symptom burden and potentially evolving disease.

• Older patients face significantly more complex surgeries, higher complication rates, and dense fibrosis.

Limitations to Keep in Mind: This study only evaluated patients who underwent surgery. It does not represent patients managed exclusively with medical therapy, nor does it map the natural progression of the disease without surgical intervention. Therefore, these findings reflect surgical population dynamics, not full disease epidemiology.

At ESSI: Translating Evidence Into Care

Endometriosis is not simply a disease that “keeps getting worse over time.” Instead, it is a disease that evolves—early in its severity, and later in its complexity. Understanding that distinction is critical when discussing the timing of intervention, surgical planning, and long-term disease management.

At Endometriosis Surgical Specialists International (ESSI), our approach is grounded in exactly this type of data. We continuously follow and integrate the most recent research to better understand how endometriosis behaves across different stages of life—not just in theory, but in real surgical practice.

This evidence-based approach allows us to:

• Approach each patient with an age-specific and phenotype-driven perspective.

• Anticipate surgical complexity well beyond what standard clinical staging might suggest.

• Support highly informed, individualized decision-making for our patients.

Because our understanding of endometriosis is not static, the way we manage it shouldn’t be either.

Study Reference: Yagur Y, Schneyer RJ, Hamilton KM, Ezike O, Ciesielski K, Barker M, Thrift C, Fitzsimmons K, Levin G, Meyer R, Wright KN, Siedhoff MT. Is endometriosis a progressive disease? Examining age-related trends in disease severity and surgical complexity. Fertility and Sterility. 2026;125(3):477–487. doi:10.1016/j.fertnstert.2025.09.024