..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.
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Study population
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Finding
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Link
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3680 members of the endometriosis association surgically diagnosed
with endometriosis
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Overall allergies and asthma were reported in 61% of women with endo,
compared to 18% of the general US population
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4331 members of the endometriosis association surgically diagnosed
with endometriosis
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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
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*Increased
risk in ovarian cancer mostly attributed to women aged 50+ with a long
standing history of ovarian endometriosis
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138 women aged 24 or under diagnosed with endometriosis
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Asthma present in 22.5% of women
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467 women diagnosed with endometriosis, 412 women without
endometriosis
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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
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113 women diagnosed with endometriosis, 170 people of both genders
from the general population
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More women with endometriosis tested positive on a prick test for
allergies (45.6%), than those of the general population (24.7%)
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501 women diagnosed with endometriosis, 188 women without
endometriosis
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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
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43 women with endometriosis, 43 women without endometriosis
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Eczema, hay fever and food sensitivities were significantly more
common in women with endometriosis
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37,661 women diagnosed with endometriosis identified from the Danish
Hospital Discharge register from 1977-2007
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No increase in the risk of multiple sclerosis, systemic lupus erythematosus
or Sjorgren syndrome were observed for women with endometriosis
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37,661 women diagnosed with endometriosis identified from the Danish
Hospital Discharge register from 1977-2007
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Women with endometriosis were found to be at a higher risk of
inflammatory bowel disease, Crohn’s disease and ulcerative colitis.
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7,259 women with endometriosis, 535,818 women without
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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.
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120 women diagnosed with endometriosis and 1,500 healthy women having
blood tests and intestinal biopsy for celiac disease
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Celiac disease was found in 2.5% of the women with endometriosis
compared to 0.66% of the endo-free women
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223 women diagnosed with endometriosis 246 women without
endometriosis having blood tests for celiac disease
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Celiac disease was found in 2.2% of women with endometriosis compared
to 0.8% of the endo-free women
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34 patients with endometriosis, 37 without endometriosis undergoing hysterectomy
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Chronic endometritis (inflammation of the endometrium) was observed
in 53% of women with endometriosis and 27% of the women without endo
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1,618 women with a preoperative clinical and ultrasound diagnosis of
endometriosis
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Adenomyosis was found in 21.8% of these women. Adenomyosis was
significantly associated with deeply infiltrating endometriosis
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331 women undergoing surgery for benign gynaecological conditions
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Endometriosis was found in 28% of women with fibroids and 43.5% of
women with adenomyosis
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182 women with endometriosis, 240 women with uterine fibroids, 183
women undergoing laparoscopic sterilisation
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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
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220 premenopausal women aged 40-50 years old undergoing hysterectomy
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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
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143 women undergoing MRI who had a previous history of endometriosis
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Depending on the criteria used for diagnosing adenomyosis, the co-occurrence
of adenomyosis in endometriosis patients varied from 58-91%
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257 women with confirmed endometriosis, 253 women with no history of
endo symptoms
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Fibromyalgia was found in 0.78% of women with endo and 0.79% of women
without endo
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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
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Women with endometriosis were found to be at a higher risk of
migraine than the endo-free women
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6,076 women with endometriosis, 30,380 endo-free controls taken from
the National Health Insurance Research Database of Taiwan from 2000-2005
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Irritable bowel syndrome was diagnosed in 4.2% of the women with endo
and 2.2% of the women without
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101 women surgically diagnosed with endometriosis
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Irritable bowel syndrome was diagnosed in 14% of these patients
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Nine studies including 1,016 patients with chronic pelvic pain
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Endometriosis and interstitial cystitis were found together in 48% of
patients
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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.
