Researchers studied nearly 4,000 women to understand why some develop endometriosis, a painful condition where tissue grows outside the uterus. They found that women with higher ratios of “bad” to “good” cholesterol were more likely to have endometriosis. The study also discovered that inflammation and nutritional markers partially explained this connection. While this is an important finding, it suggests that managing cholesterol levels through diet and lifestyle might help reduce endometriosis risk, though more research is needed to confirm this.

The Quick Take

  • What they studied: Whether the ratio of bad cholesterol to good cholesterol (called NHHR) is connected to endometriosis, and whether inflammation and nutrition markers explain this connection.
  • Who participated: 3,994 women from a large U.S. health survey conducted between 2001-2006. About 287 of these women (7%) had endometriosis.
  • Key finding: For every unit increase in the bad-to-good cholesterol ratio, women had a 14.3% higher chance of having endometriosis. About 14% of this increased risk appeared to be explained by inflammation and nutritional markers.
  • What it means for you: If you have endometriosis or are at risk, managing your cholesterol levels through diet and exercise might help. However, this study shows a connection, not proof that cholesterol causes endometriosis, so talk to your doctor about your individual situation.

The Research Details

This was a cross-sectional study, which means researchers looked at a large group of women at one point in time and compared those with endometriosis to those without it. They used data from the National Health and Nutrition Examination Survey (NHANES), a well-respected U.S. government health study that collects medical information and blood tests from thousands of Americans.

The researchers measured cholesterol levels in the women’s blood and calculated a special ratio: non-high-density lipoprotein (the “bad” cholesterol) divided by high-density lipoprotein (the “good” cholesterol). They also measured inflammation markers and nutritional status using something called the CALLY index, which combines information about inflammation, protein levels, and immune cells.

They used statistical methods to see if higher cholesterol ratios were linked to endometriosis, and whether the inflammation and nutrition markers explained part of this connection.

Cross-sectional studies are useful for finding connections between health factors, though they can’t prove one thing causes another. This approach was appropriate because it allowed researchers to look at many women’s real-world health data. The use of a large, representative sample from NHANES makes the findings more likely to apply to the general population.

Strengths: Large sample size of nearly 4,000 women, use of standardized health survey data, careful statistical adjustments for other factors that might affect results, and confirmation of findings in different subgroups. Limitations: This is a snapshot in time, so we can’t prove cholesterol causes endometriosis; the data is from 2001-2006, so it may not reflect current populations; and we can’t know if unmeasured factors played a role.

What the Results Show

The main finding was that women with higher bad-to-good cholesterol ratios (NHHR) were more likely to have endometriosis. Specifically, for every one-unit increase in this ratio, the odds of having endometriosis increased by 14.3%. This relationship held true even after the researchers accounted for other factors like age, body weight, and smoking status.

The researchers also tested whether this relationship was consistent across different groups of women (different ages, weights, and health conditions). The connection remained fairly stable across these groups, suggesting the finding is fairly robust.

When the researchers looked at the dose-response relationship (meaning whether higher cholesterol ratios meant even higher endometriosis risk), they found a linear pattern—basically, the higher the cholesterol ratio, the higher the risk.

The mediation analysis revealed that inflammation and nutritional markers (measured by the CALLY index) explained about 14% of the increased endometriosis risk associated with high cholesterol ratios. This means that part of the way bad cholesterol ratios might increase endometriosis risk is by causing inflammation and affecting nutritional status. However, 86% of the connection remains unexplained, suggesting other mechanisms are also involved.

This study adds to growing evidence that lipid (cholesterol) metabolism is connected to endometriosis. Previous research has suggested that inflammation plays a major role in endometriosis development. This study is novel because it specifically looks at the cholesterol ratio (bad to good) rather than individual cholesterol levels, and it identifies inflammation as a partial explanation for the connection.

This study cannot prove that high cholesterol ratios cause endometriosis—it only shows they’re connected. The data is from 15-20 years ago, so current populations might be different. The study relied on self-reported endometriosis diagnosis rather than confirmed medical records. We don’t know if other unmeasured factors (like diet quality, exercise, or stress) might explain the connection. Finally, because this is a snapshot study, we can’t determine the timing of events or whether cholesterol changes preceded endometriosis development.

The Bottom Line

If you have endometriosis or family history of it, ask your doctor to check your cholesterol levels and cholesterol ratio. Focus on heart-healthy habits: eat more fruits, vegetables, and whole grains; limit saturated fats; exercise regularly; and maintain a healthy weight. These changes may help reduce endometriosis risk, though more research is needed. Confidence level: Moderate—this study suggests a connection, but we need more research to confirm causation.

Women with endometriosis or those at risk (family history, severe period pain) should pay attention to this. Women concerned about endometriosis prevention may also benefit from managing cholesterol. This is less relevant for men, though the cholesterol management advice applies to everyone for heart health.

Cholesterol changes from diet and exercise typically take 3-6 months to show up in blood tests. Endometriosis symptoms might take longer to improve, so patience is important. Talk to your doctor about realistic expectations for your situation.

Want to Apply This Research?

  • Track your cholesterol ratio (non-HDL divided by HDL) every 3 months. Also log inflammation markers if available from blood work, and note endometriosis symptom severity (pain level 1-10) weekly to see if improvements in cholesterol correlate with symptom changes.
  • Set a goal to improve your cholesterol ratio through diet: aim for 2-3 servings of fatty fish per week, add a serving of soluble fiber daily (oats, beans, apples), and reduce saturated fat intake. Use the app to log these foods and track how they affect your cholesterol numbers over time.
  • Create a quarterly check-in reminder to review your cholesterol numbers with your doctor. Use the app to track trends in your cholesterol ratio alongside symptom severity. If you see improvements in your ratio, note any corresponding changes in pain or other endometriosis symptoms to identify your personal patterns.

This research shows a connection between cholesterol ratios and endometriosis but does not prove that one causes the other. Endometriosis is a complex condition with many contributing factors. This information is for educational purposes only and should not replace professional medical advice. If you have endometriosis or suspect you might, consult with your healthcare provider for proper diagnosis and personalized treatment. Do not make significant changes to your diet, supplements, or medications without discussing them with your doctor first. This study is based on data from 2001-2006 and may not reflect current medical understanding or populations.