Please don’t hate us because we’re men.

As a young male, I have formed the opinion that in many respects, the female gender has drawn the shorter end of the evolutionary stick. Here are a few points that illustrate how I came to this conclusion. As I watched a television program documenting a gruelling 36-hour baby-delivery on The Learning Channel a few nights ago, every sweat-drenched, pain-induced scream emitted by the soon-to-be mother made me thankful that I, like all of my male brethren, was born without a uterus. Being the proud owner of a mother that is reluctantly entering her senior years, I have also been witness to another peculiarity of the female species – the emotional and physical chaos that is menopause. Men have thankfully never had to deal with mood swings or hot flashes. And of course, women will forever be envious of the luxury we males have of being able to urinate while standing! If these and the plethora of other injustices attributed to having 2 copies of the notorious X-chromosome were not enough, women face yet another threat to their gender …Irritable Bowel Syndrome (IBS). IBS affects more females than males with ratios sometimes reported being as high as 3:1. Furthermore, a recently published study has indicated that women, who use Hormone Replacement Therapies (HRT), like those prescribed for the symptoms of menopause, are at an increased risk of developing IBS.

IBS is a multi-component condition characterized by heightened gut sensitivity, altered intestinal motility and impaired secretory function. IBS is one of the most common ailments seen in the primary care setting affecting approximately 10-20% of the general population.1 Despite its prevalence, researchers and health practitioners have yet to formulate firm conclusions regarding the etiology of IBS, proper classification and diagnosis, and the most effective treatment strategies. With all these fundamental questions unanswered, it is not surprising that there have been few studies aimed at characterizing the differences between females and males in IBS. Of the few studies that have looked at these gender differences, in addition to an increased rate of occurrence, preliminary results have indicated that women diagnosed with IBS report an overall lower quality of life and a greater number of symptoms including nausea, constipation, bloating, as well as various other extracolonic symptoms (e.g. urinary urgency, and muscle stiffness).2 Researchers have postulated that differences in hormonal factors, responses to stress, and other psychological factors may account for the dissimilarities observed between men and women.

While there is a general consensus among IBS researchers that the disease afflicts more females than males, a study by Ruigómez et al. reported that the rate of occurrence of IBS among females was observed to decrease as age increased.3 At ages over 70, the rate of incidence among females was comparable to that of males. In males, however, the occurrence of IBS was relatively constant across all age groups. The authors proposed that the decline in incidence observed in women was related to the lowered estrogen that is the characteristic impetus of menopause. This prompted Ruigómez group to investigate if there was any correlation between HRT (the use of oral or transdermal regimens of synthetic female sex hormones) and the development of IBS.

40,199 HRT users aged 50-69 without prior diagnoses of gastrointestinal disease were compared to a matched cohort of 50,000 women who had never used HRT.4 Subjects were studied from the start date until the earliest occurrence of one of the following: a diagnosis of IBS was made, the subjects reached the age of 70, the subjects expired, the subjects were excluded due to extraneous factors (e.g. alcohol abuse or cancer), or the study period ended.

At the end of the study, 660 women were confirmed to have developed IBS. Of those confirmed cases, the incidence rate of IBS among non-HRT users was assessed to be 1.7 per 1,000 person-years while the rate among HRT users was 3.8 – almost a twofold increase. These results were consistently observed regardless of the specific regimen of HRT prescribed, route of administration (oral or transdermal), or duration of treatment. Ruigómez et al. concluded that the increased risk of developing IBS as a result of HRT use was due to the presence of exogenous estrogens. These estrogens acted in a similar manner to naturally occurring endogenous sex hormones that circulate at higher concentrations before menopause. By eliciting a yet to be defined physiological mechanism, these heightened levels could very well be responsible for the observed preponderance of female IBS patients over males.

In addition to the previously reported age and sex-related factors of IBS, its recently documented association with HRT has, like all good science, provided more inquiries than answers. Why is the IBS gender bias observed and can the manipulation of hormonal influences on the gut be used as a potential target for future IBS therapies? As IBS research continues, hopefully these questions will be resolved. Until then, women will have to continue to carry the increased susceptibility to IBS among the other burdens Mother Nature has bestowed upon the female gender. But perhaps if scientists discover how to allow men to carry babies to term, the increased risk of IBS will be a bit easier for women to bear.

Andrew Ming-Lum, BScH
First published in the Inside Tract® newsletter issue 139 – September/October 2003
1. Jones, R., et al. (1992) Irritable bowel syndrome in the general population. British Medical Journal. 302:87-90
2. Chang, L., et al. (2002) Gender differences in Irritable Bowel Syndrome. Gastroenterology. 123:1686-1701
3. Rodriguez, G., et al. (2000) Detection of colorectal tumor and inflammatory bowel disease during follow-up of patients with initial diagnosis of irritable bowel syndrome. Scandinavian Journal of Gastroenterology. 35(3):306-11
4. Ruigómez, A., et al. (2003) Is hormone replacement therapy associated with an increased risk of irritable bowel syndrome? Maturitas 44(2):133-40