Monday 10 August 2015

Misery loves company..

..and endometriosis is that proverbial misery. Very rarely have I encountered someone with endo who only has endo. However, knowing what conditions are actually associated with endo and which ones just occur by chance is important to build up a complete picture of what it actually means to suffer from endometriosis and that, for some women, it is not just about the lesions.

Below is a table summarising some of the studies looking at which conditions are, or aren’t, associated with endo. It is by no means an exhaustive list of the studies into comorbidities and endo because that would’ve taken a very long time. But I have tried to include all the major studies and the ones I think people will find most interesting. There’s also some studies that just don’t exist, which I would’ve like to include. For example, I couldn’t find any good studies on the association between endometriosis and polycystic ovarian syndrome (PCOS), which was a shame.

Sorry about the long boring table with a bunch of dry stats and figures, buts that the reality of science unfortunately.

Study population
3680 members of the endometriosis association surgically diagnosed with endometriosis
% women in this study
% women in general population
Systemic lupus erythematosus
Multiple sclerosis
Rheumatoid arthritis
Sjogren’s syndrome
Diabetes melitus
Chronic fatigue syndrome

Overall allergies and asthma were reported in 61% of women with endo, compared to 18% of the general US population

4331 members of the endometriosis association surgically diagnosed with endometriosis
% women in this study
% women in general population
Breast cancer
Ovarian cancer*
Non-hodgkins lymphoma
Recurrent upper respiratory tract infection
Recurrent vaginal infections
Addison’s disease
Cushing’s syndrome
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37,434 women diagnosed with endometriosis on the National Swedish Inpatient Register cross-referenced with the National Swedish Cancer Register between 1969 and 2000
Cancer type
Number of cases observed in endo patients
Number of cases expected (based on general population)
Ovarian *
Non-Hodgkin’s lymphoma
All cancers
*Increased risk in ovarian cancer mostly attributed to women aged 50+ with a long standing history of ovarian endometriosis

138 women aged 24 or under diagnosed with endometriosis
Asthma present in 22.5% of women

467 women diagnosed with endometriosis, 412 women without endometriosis
4.9% of the women with endo reported having asthma, 5.3% of the women without endo reported having asthma, no difference between severity of asthma was observed between the groups

113 women diagnosed with endometriosis, 170 people of both genders from the general population
More women with endometriosis tested positive on a prick test for allergies (45.6%), than those of the general population (24.7%)

501 women diagnosed with endometriosis, 188 women without endometriosis
9% of the women with endo reported having asthma, compared to 4.3% of women without
56.7% of the women with endo reported having allergies compared to 23.4% of women without
No differences were observed between different stages of endometriosis
48.3% of women with endo reported a family history of allergies compared to 9.6% of women without

43 women with endometriosis, 43 women without endometriosis
Eczema, hay fever and food sensitivities were significantly more common in women with endometriosis

37,661 women diagnosed with endometriosis identified from the Danish Hospital Discharge register from 1977-2007
No increase in the risk of multiple sclerosis, systemic lupus erythematosus or Sjorgren syndrome were observed for women with endometriosis

37,661 women diagnosed with endometriosis identified from the Danish Hospital Discharge register from 1977-2007
Women with endometriosis were found to be at a higher risk of inflammatory bowel disease, Crohn’s disease and ulcerative colitis.

7,259 women with endometriosis, 535,818 women without
A higher rate of nickel allergy was observed in women with endometriosis, no increase in risk of allergic rhinitis, atopic dermatitis and contact dermatitis was observed.

120 women diagnosed with endometriosis and 1,500 healthy women having blood tests and intestinal biopsy for celiac disease
Celiac disease was found in 2.5% of the women with endometriosis compared to 0.66% of the endo-free women

223 women diagnosed with endometriosis 246 women without endometriosis having blood tests for celiac disease
Celiac disease was found in 2.2% of women with endometriosis compared to 0.8% of the endo-free women

34 patients with endometriosis, 37 without endometriosis undergoing hysterectomy
Chronic endometritis (inflammation of the endometrium) was observed in 53% of women with endometriosis and 27% of the women without endo

1,618 women with a preoperative clinical and ultrasound diagnosis of endometriosis
Adenomyosis was found in 21.8% of these women. Adenomyosis was significantly associated with deeply infiltrating endometriosis

331 women undergoing surgery for benign gynaecological conditions
Endometriosis was found in 28% of women with fibroids and 43.5% of women with adenomyosis

182 women with endometriosis, 240 women with uterine fibroids, 183 women undergoing laparoscopic sterilisation
Of the women aged 35-39, 5.7% of the control group had fibroids, 14.1% of the endometriosis group had fibroids

Of the women aged 40-44, 11.6% of the control group had fibroids, 25% of the endometriosis group had fibroids

Of the women aged 45+, 22.2% of the control group had fibroids, 46.5% of the endometriosis group had fibroids

220 premenopausal women aged 40-50 years old undergoing hysterectomy
Endometriosis was found in 40.4% of women with adenomyosis, 22.7% of women with fibroids and 34.1% of women with both adenomyosis and fibroids

143 women undergoing MRI who had a previous history of endometriosis
Depending on the criteria used for diagnosing adenomyosis, the co-occurrence of adenomyosis in endometriosis patients varied from 58-91%

257 women with confirmed endometriosis, 253 women with no history of endo symptoms
Fibromyalgia was found in 0.78% of women with endo and 0.79% of women without endo

Records of 20,220 patients with endometriosis, 263,767 endo-free controls taken from the National Health Insurance Research Database of Taiwan from 2000-2007
Women with endometriosis were found to be at a higher risk of migraine than the endo-free women

6,076 women with endometriosis, 30,380 endo-free controls taken from the National Health Insurance Research Database of Taiwan from 2000-2005
Irritable bowel syndrome was diagnosed in 4.2% of the women with endo and 2.2% of the women without

101 women surgically diagnosed with endometriosis
Irritable bowel syndrome was diagnosed in 14% of these patients

Nine studies including 1,016 patients with chronic pelvic pain
Endometriosis and interstitial cystitis were found together in 48% of patients

You may notice that some of the studies are contradictory or in disagreement. The reason for this is usually differences in the design of each study. Some studies might separate patients by stage of endo, whereas other lump them all together in one group. Generally the more participants in each study the more representative it will be of the population being studied. Another factor is how the data from each patient is collected; is it collected by reviewing medical records, or is it from surveys patients have filled out where they had to recall information? The latter is always more accurate than the former. Yet another point is, if the study is comparing women with and without endo, how are the different groups chosen? For example, do the women in the endometriosis group have a surgical diagnosis? Or just an imaging method diagnosis , like ultrasound? What about the group they are being compared to, are they ‘endo-free’ or ‘healthy’ controls? An endo-free control group could include women with other health conditions, whereas a ‘healthy’ control groups should have no other chronic illnesses.

Another point along these lines is how the women with and without endometriosis are ‘matched’. Matching is basically comparing like with like and it is an important aspect to consider when conducting studies like the ones above. After all, would it be accurate to compare a 20 year old, non-smoker with a BMI of 18, with a 65 year old, smoker with a BMI of 34? Definitely not. All of these factors can influence the results of a study.

So what can we learn from these studies? Firstly it’s important to interpret the information in the correct way. For instance, when looking at the studies on how common endo is in women with fibroids and adeno, it’s important to know how common each of those conditions is in the general population, which is why it’s handy that some studies give the incidence of other conditions in the general population. Fibroids are extremely common (around 50-70% of women will have fibroids by the time they are 50 years old) so finding fibroids in women with endo is no big surprise (although some studies suggest fibroids might be more common in endo women). However, adenomyosis is thought to affect around 8-20% of women. So studies finding adenomyosis in nearly half of women with endo (or more) clearly suggest and association between the two conditions (and being that adenomyosis is displaced endometrial-like tissue inside the wall of the uterus, rather than outside the uterus itself, the two conditions could have a shared origin).

All of the studies agree that there is no overall increased risk of cancer for women with endometriosis, however there does seem to be some small increases in risk for ovarian cancer. This increase can be attributed to women with long standing ovarian endometriosis, but on the plus side, another study has shown that women with endometriosis and ovarian cancer have a much higher survival rate than women with ovarian cancer but without endo.  This is most likely due to increased monitoring of women with endo (more ultrasounds/laparoscopies etc).

This raises another interesting point to think about. Could the increase in diagnosis of certain health conditions in women with endo actually be due to under diagnosis in the general population? Women with endo are likely more aware of their own health status, because having a chronic illness means you are constantly paying attention to your health. Also because women with endo have more doctors’ visits, more scans and more investigatory procedures while navigating the minefield that is endo diagnosis and treatment, they are more likely to have other health conditions diagnosed as well.

There also seems to be an increase in the co-occurrence of allergies, asthma and immune disorders in women with endo. There are a multitude of studies showing alteration of different components of the immune system in women with endometriosis. In particular endometriotic lesions secrete chemical messages that activate a type of immune cell called a macrophage. The macrophages produces certain chemical messages that activate other types of immune cells, called Th2 cells, that then go on to activate the immune cells responsible for allergic inflammation. What all that means is that the presence of endometriosis could prime the immune system to be more sensitive to allergic stimuli, perhaps explaining the higher occurrence of allergies and asthma in women with endo.

What this also means is that endometriosis isn’t always just about endometriosis. Often there are other health conditions found in association with endo, meaning that simply focussing on one isn’t enough and that a broad, multidisciplinary view is needed when treating women with endo.


  1. Absolutely true in the case of immune system issues as well as allergies in general with endo and adeno.

  2. Interesting the amount diagnosed with respratory infections. I was repeatably diagnosed with this until they found endo. I wonder with the amount of women on hormones that it's not little clots from the estrogeon or misdiagnosed pulmonary endo or diaphragmic seeding. I too also get bad allergies a few days before I'm due do bad sometimes eyes puff up and close as well as rash over things that don't give me strife at any other time of the month.

  3. Your penultimate paragraph is what I have been saying for years - with no scientific data to back me up until now. Thank you - you've confirmed my theory!


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