Wednesday, 29 April 2009
Okay by now you’re probably wondering where I’m going with this but bare with me. The reason I’ve put in all the preceding text is that a study has just been published in the Scandinavian Journal of Work, Environment and Health which found that women who work as a flight attendant, service station attendant or nurse may be more likely to have endometriosis. Again this is a fairly well designed an executed study, but couldn’t it all just be a coincidence like the car colours?
Well for starters, although this study seems well designed there are definite problems with it, mainly what is known as sample size. Basically if you are going to compare one group of people with another for whatever reason, the more people you have the better as it narrows the likelihood of errors occurring in the proceeding analysis. This study took 341 women with endometriosis and 742 women without endometriosis, which may seem like a lot and would be fine, but these large groups were then divided by job type. So for example, in the service station attendant category they were only comparing 4 women with endo to 2 women without, and in flight attendant category 5 women with endo were compared with only 1 without.
That’s the first problem, the second is the significance of the results. Say you had compared one group of people with another and found a difference between them. How do you know that difference is significant? Well scientists have long boring equations that you put your results into and it pops out with a number called the P value. If the P value is less than 0.05 then the result is significant, if the P value is less than 0.01 then it is really significant. Anything above 0.05 is considered pretty unconvincing. The authors of this study have put their results into these tedious but necessary equations and found that although there was a difference in the number of women with endo in these different job groups they were not significant. The nurse job group, for example, had a P value of 0.23, which is suggestive, but definitely not what is considered significant.
There is also the assumption that job has any bearing on endometriosis risk. Certain authors have said that exposure to certain environmental toxicants may have an effect on developing endometriosis and the level of these toxicants varies with job type. This has never been proven thought, so we must treat this assumption with some caution. For example there was a study that suggested women who work in wood and paper mills may be more likely to develop endometriosis due to exposure to certain chemicals involved in the wood processing industry. However, it must be remembered that no environmental chemical has ever been unequivocally proven to increase the incidence of endometriosis in humans.
In conclusion the study of relationship between job title and endometriosis is an area worthy of investigation but I personally doubt any job type confers an increased risk of developing endometriosis. Endometriosis is such a complicated disease it is far more likely that a whole host of factors play a role in risk of developing the disease. So don’t go changing your job (or your car) just yet.
If you would like to read the full article from the Scandinavian Journal of Work, Environment and Health, follow the download link on this page
Monday, 20 April 2009
You may have heard about some of the theories going around. Retrograde menstruation is the go-to theory for explaining how endometriosis comes to be. This basically states that during a period although most of the blood exits via the vagina, some of the blood travels upward into the fallopian tubes and out into area surrounding your various reproductive organs. This blood contains endometrial tissue (that normally lines the womb) which is thought to implant on the organs it settles on and grow to become endometriosis. There’s a neat little animation explaining how retrograde menstruation works on the Endometriosis Research Foundation website and can be found here.
The problem with this theory is that it has been found that 90% of women experience retrograde menstruation, so how come only 10% of women get endometriosis? The retrograde menstruation theory also assumes that menstruation is nessacary for endometriosis to develop. Well an interesting study has just been published in the journal of Experimental and Clinical Cancer Research which has presented some new evidence suggesting women are born with endometriosis.
This study took on the task of dissecting 36 human female foetuses, which had either been aborted or died of natural causes, and looked for evidence of displaced endometrial tissue, the hallmark of endometriosis. What they found was that out of the 36 foetuses, 4 showed evidence of endometriosis. This was remarkable for two reasons, one for the fact that endometriosis had apparently been found in developing foetuses, suggesting that women are in fact born with endometriosis, and two because 4 out of 36 individuals with endometriosis is roughly what you would expect to find in an adult female population.
As interesting as this is, the question remains, how does this displaced endometrial tissue get there? Retrograde menstruation clearly cannot be the answer. The authors of this research suggested that there is an error during the foetal development of the reproductive organs. You see when the foetus is in its very early stages of development it is neither male nor female, it has two sets of ducts, the Wolffian duct (which goes on to become the male reproductive organs) and the Müllerian duct (which goes on to become the female reproductive organs). There is a nice diagram of the various ducts and how they develop here.
The body sends signals to these ducts telling them to become the correct part. So if you were a female the Wolffian duct would disappear and your body would send signals to different parts of the Müllerian duct saying “ok this bit becomes an ovary, this bit becomes a uterus, this bit is the endometrium, this bit becomes a vagina etc etc”. The trouble comes when these signals get muddled (possibly environmental toxicants are messing up the signal, or the messages your DNA is sending are wrong) you get the wrong bits growing in the wrong place. This is basically what these researchers are suggesting, that during the body’s early development, the signals are getting mixed for whatever reason and bits of endometrium end up developing where they shouldn’t (this is called ‘Müllerianosis’), then when puberty hits these bits of displaced endometrium that have been lying dormant since birth become active, and the result is endometriosis.
Overall it’s an interesting new theory on the origin of endometriosis to consider however, there will need to be much more investigation along this line before it is widely accepted, but provides the background work for future research. Additionally if this theory becomes accepted then the next question to ask will be “So what’s messing up the signals?” You can read the article in its entirety by following the links on this page.
Sunday, 19 April 2009
It may just be a personal dislike of this particular description but I feel justified in saying that the disease already has a name, why not just call it that? After all you don’t see diabetes reported with the sideline “pancreatic insulin condition” or cancer with a little note saying “deadly cellular proliferation and metastasis condition”. Endometriosis is called endometriosis, that’s it name, we’re not idiots who need a little description in normal people language every time we see a word with more than 3 syllables.
It’s not just the feeling of ‘dumbing-down’ I get every time I see “painful womb condition”, it’s the fact that it’s not a very accurate description. Endometriosis affects the outer surface of the womb, and many other areas. The media outlets even gleefully contradict themselves by stating this. For example, in the GMTV link mentioned above they refer to endometriosis as a “womb condition” then go on to say “Endometrial tissue can also be found in the ovary where it can form cysts and may affect fertility”. This link from the Evening Standard also starts off labelling endometriosis “A painful womb condition” then ends by saying ” The disorder can occur in several places in the body, most commonly the fallopian tubes, ovaries, bladder, the bowel, the intestines, the vagina and the rectum”. It seems like the people writing these articles are having some sort of disagreement with them self about what body part endometriosis affects.
So there are good and bad points about endometriosis being reported in the media. 1) it raises awareness, but 2) It creates confusion by not describing the disease properly. So, in conclusion, if you are a journalist and you must find a suitable tag with which to label endometriosis just call it a “painful condition” or better yet, just call it endometriosis.
Wednesday, 15 April 2009
A surgical procedure is often required for women with endometriosis if drug treatments fail to control the symptoms, but how successful are the different types of surgery? An American study published last year in the Journal Obstetrics and Gynaecology reported the success rates of three different types of surgery:
- Excision of endometriosis alone
- Hysterectomy without removing ovaries
- Hysterectomy with removing ovaries
The study followed patients undergoing these procedures and noted whether they required further surgery after 2, 5 and 7 years. The results were as follows:
Of the women who underwent excision of endometriosis only:
After 2 years 30.6% of women needed further surgery
After 5 years 46.7% needed more surgery
After 7 years 65.4% needed more surgery
Of the women who underwent hysterectomy, but kept their ovaries:
After 2 years 4.3% of women needed further surgery
After 5 years 13.4% needed further surgery
After 7 years 23% needed further surgery
Of the women who underwent hysterectomy and ovary removal:
After 2 years 4% of women needed further surgery
After 5 years 8.3% needed further surgery
After 7 years 8.3% needed further surgery
So it would appear that surgical excision of endometriosis alone is associated with a high rate of recurrent surgical procedures. Hysterectomy with ovary removal was the most successful (but least appealing) procedure. One thing to consider though, is that the abstract for this paper did not state whether the patients participating in this study were taking any medical therapy and whether this affected their recovery rates.
A link to the article can be found here
I’m not just voicing opinion here either, I know of several cases where the symptoms of endometriosis have returned after pregnancy. Additionally, a recent article published in the journal Fertility and Sterility reported a study from Japan which found that rates of ovarian endometriosis during pregnancy have actually increased and, in fact, nearly quadrupled.
The facts were these; during the period from 1996-2001 the incidence of ovarian endometriosis was 0.14%, or 5 cases of ovarian endometriosis out of 3558 deliveries. This rose sharply during the period of 2002-2007 to 0.52%, or 19 cases out of 3599.
Now although these incidence rates are fairly low, the mere existence of these statistics indicates quite clearly that the assumption ‘pregnancy cures endometriosis’ is a false one.
A link to the article in question is provided here