Impact of Female Gender in Inflammatory Bowel Diseases: A Narrative Review.

IBD epidemiology is complex. The prevalence is related to the type of disease studied (e.g., CD instead of UC), the geography of the investigated area, and the age of the considered subjects. Gender-related differences have been found in the epidemiology of CD but were not so marked in UC [ 4 ]. Indeed, except for two studies observing a male preponderance over the UC epidemiology [ 5 , 6 ], investigations conducted both in East and West countries agreed that there was no gender-based disparity in the epidemiology of UC [ 7 , 8 , 9 ]. Shah et al., in a pooled analysis of population-based studies on 95,605 and 112,004 incident cases of CD and UC, respectively, found that age at UC onset varied with sex. Indeed, the incidence of UC is similar between males and females until age 45. After this age, females showed a 13% to 32% lower likelihood of being diagnosed with UC than males [ 10 ]. In contrast, there are sex-specific differences in CD, with women predominating in the USA and European countries [ 9 , 11 , 12 , 13 , 14 , 15 ], conversely to what occurs in Asian countries, where males are more prone to CD [ 16 , 17 ]. This evidence suggests that CD occurrence is not strictly sex-related, but other environmental factors, such as the westernization of lifestyle, could play a pivotal role in IBD pathogenesis. A recent pooled analysis of population-based studies considering 17 distinct cohorts of patients from 16 regions of Europe, North America, Australia, and New Zealand suggested that puberty in women is a trigger for CD onset, as the risk of developing the illness is 20% lower in girls than boys at age 10–14, but it markedly increases for women reaching the age of 25–29, and in particular after 35 years. A Dutch study investigating a large sample size ( n > 5700) and two independent cohorts confirmed a low risk for very young women. The analysis revealed a male prevalence in early-onset CD (<16 years) compared to females (20% vs. 12%, p < 0.01) [ 18 ]. These findings support the hypothesis that female sex hormones play a role in IBD pathogenesis.

Genetic factors are involved in IBD etiology. In familial clusters of IBD, a female preponderance has been reported (61% vs. 54% compared to sporadic IBD, respectively) [ 19 ]. The increased relative risk for females is promoted by sex-determined epigenetic factors responsible for the female-to-female transmission pattern. This aspect, referred to as “female imprinting”, was found to be particularly recurrent in familial CD (31 mothers vs. 14 father-to-child transmissions, respectively; p = 0.016) [ 19 ]. Moreover, several gene variants contribute to the family-specific risk of IBD. An Italian study on 203 sporadic UC patients and 391 controls correlated interleukin (IL)-10 promoter polymorphisms to a higher risk of developing UC at younger ages in females. This effect may be enhanced by estrogens that inhibit the production of anti-inflammatory cytokines, i.e., IL-10 [ 20 ]. Another study on the Pennsylvania population showed that women carrying a variant of the IL-23 receptor are protected against CD and IBD overall. Another variant of the same receptor is particularly protective against UC [ 21 ]. Intriguingly, some genetic mutations appear to be only male-specific. A study on 61 IBD patients and 101 subjects without IBD from the Lower Silesia region revealed that the 3435CT polymorphism of the ABCB1 gene is an IBD and CD-promoting factor in males. In contrast, the 3435TT polymorphism of the same gene is associated with a reduced risk of IBD in men [ 22 ]. Also, compared with 139 healthy controls, a pedigree genotyping of 105 IBD subjects showed a male predominance associated with the DLG5 R30Q variant, confirming previous findings [ 23 ]. The same variant has been indicated as a protective factor in female pediatric CD onset [ 24 ]. The female genetic predisposition to develop IBD is also related to X chromosome abnormalities, such as Turner syndrome [ 25 ]. In IBD-affected relative pairs, X-linked susceptibility loci have been identified [ 26 , 27 ]. In a murine model, the loss of one allele of the Cosmc X-linked gene evoked gut dysbiosis, enhanced experimental colitis, and a spatial pattern of dysbiosis resembling IBD in males but not in female mice. One allele of this gene that encodes for a chaperone involved in the sex-specific risk of CD and UC was found to be protective against an IBD-like phenotype only in female mice [ 28 ]. These findings suggest that in females, other mechanisms regulate the enteric mucosa (broadly “glycocalyx”) and neuromuscular layer integrity. While mosaicism strengthens immunity in females vs. males, an inappropriate inactivation of some regions of the X chromosome could lead to an immune system derangement. This condition promotes a breakdown of self-tolerance [ 29 ] and favors autoantibodies [ 30 ] and the genesis of immune disorders, such as primary biliary cholangitis, autoimmune thyroid disease, Reynolds syndrome, and systemic sclerosis [ 30 , 31 ]. Although the complex mechanisms involving the X chromosome and autoimmune diseases have not been elucidated yet, a possible direction for further studies is represented by the naturally occurring variations in X-related genes and microRNAs taking part in the immune system arrangement. Unraveling these mechanisms may aid in a better understanding of differences between genders. Studies evaluating the incidence and prevalence of IBD by gender are summarized in Table 1 .

Studies aimed to demonstrate a possible relation between gender and IBD development reveal contrasting results. In some investigations, the female gender seems to act as a protective factor, while other studies suggest the opposite [ 32 , 33 , 34 , 35 ]. Moreover, clinical data suggest that the IBD phenotype may show gender specificity, as males tend to manifest CD in the upper GI tract [ 36 ] or ileal region [ 18 ] compared to females. Moreover, females seem to be more protected against colorectal cancer than men [ 37 ], but not from pulmonary cancer [ 38 ]. Extraintestinal manifestations (EIM) associated with IBD appear sex-dependent and affect women more than men [ 18 ]. Females actually show a higher risk of developing eye disorders, erythema nodosum, and pyoderma gangrenosum than males. Conversely, the latter are more prone to develop primary sclerosing cholangitis and ankylosing spondylitis [ 36 ]. IBD is frequently associated with complications, such as cumulative medication use, surgery, and disease recurrence after surgery [ 32 ]. A study on 260 CD patients with a follow-up of 12 years found that IBD complications affect more men than women [ 33 ]. Moreover, a second study from the Mayo Clinic supports these findings, describing a male preponderance over major abdominal surgery, including bowel and ileocecal resection [ 39 ]. A Dutch IBD biobank study showed that the male sex was more commonly associated with small bowel and ileocecal resection [ 18 ]. However, these results were contrary to the data obtained in another study on a more extensive cohort ( n = 1106 patients), which reported no gender-specific differences in IBD complications [ 32 ]. Osteoporosis and, in particular, osteopenia were surprisingly more common in men than women (55.9% vs. 29.6%, respectively, n = 174) [ 40 ]. Similar results were also found in other series, suggesting that osteopenia and osteoporosis should always be investigated in male IBD patients as they show a high risk of mineral bone abnormalities [ 41 , 42 , 43 , 44 , 45 , 46 ].

Several pharmacological and nutritional approaches are currently available to handle IBD, but their efficacy is still under evaluation because of the novelty of some of them [ 47 , 48 ]. However, clinical data show that IBD management and therapy differ between males and females. Females receive fewer IBD-specific treatments than males, while major abdominal surgery is performed more frequently in men than women [ 18 , 34 , 39 , 49 ]. A study on 986 outpatients reported that women received less immune-suppressive treatment despite their higher disease activity [ 34 ]. Many reasons may be advocated for this finding in men: (a) higher risk of developing severe disease; (b) lower compliance to corticosteroids and/or aminosalicylates; and probably (c) lower propensity to treat women of childbearing age with immunosuppressants [ 34 ]. These possible explanations were recently tested by a Canadian study in South-West Ontario [ 50 ], examining over 1000 IBD participants. The results demonstrated that women were more commonly treated with budesonide, while men were treated with prednisone, as also confirmed by Severs et al., 2018 [ 18 ]. Moreover, the use of immunomodulators is predominant in men vs. women (86.6% vs. 78.3%; p = 0.008), and, nevertheless, women were more prone to experience adverse drug reactions (29.5% vs. 21.2%; p = 0.01) [ 50 ]. The same study also found that age is predictive of biologics treatment in women, as those over 55 less frequently receive biologics. Overall, women responded better to treatment than men [ 51 ], but they displayed lower adherence to biological treatment [ 52 ]. On the other hand, males tolerate drug therapy better than females, who reported more prominent side effects. Studies assessing IBD clinical features and management are summarized in Table 2 .

Infertility is described as the impossibility of conceiving after 12 months of regular, non-protected sexual intercourse [ 53 ]. Infertility rates among IBD women were reported to range from 3–14% in CD and 1.7–15% in UC, which are comparable with rates in the general population (2.5–14%) [ 54 , 55 , 56 , 57 , 58 ]. Thus, IBD females have a fertility rate comparable to the overall population, except for women with active disease or ileal pouch–anal anastomosis (IPAA), who have higher infertility rates [ 54 ]. Studies assessing serum anti-Mullerian hormone (AMH) levels as a marker of ovarian reserve and women’s fertility support these results. Data showed similar AMH levels between IBD and healthy women, indicating no differences in infertility rates due to the pathological condition. However, a retrospective case-control study measuring AMH in 50 women with CD in remission and 163 control women with physiological ovarian reserve (matched by age) concluded that hormone levels were significantly lower in ≥30-year-old women with colonic CD involvement compared to the controls [ 59 ]. Moreover, AMH levels were lower in active disease and inversely correlated with the Crohn’s Disease Activity Index, suggesting that the active disease may compromise fertility [ 60 , 61 , 62 ]. Although evidence indicated no differences in fertility rates between IBD and healthy women, patients showed half the number of children vs. healthy women, a feature known as “voluntary childlessness” [ 58 ]. This lifestyle may be explained by both mechanical and psychological grounds. From a mechanical point of view, surgical interventions greatly affect women’s anatomy, significantly reducing their ability to conceive. UC women undergoing deep pelvic dissection show a higher risk of pelvic adhesions, formation of scar tissue, post-operative dyspareunia, tubal obstruction, or alteration of the tubal-ovarian crosstalk, causing a threefold reduction in the fertility rate [ 63 , 64 ]. A systematic meta-analysis on the relative risk of infertility post-ileal pouch-anal anastomosis in women with UC showed that infertility increased from 15% to 48% [ 65 ]. In agreement with this result, a systematic literature search considering 22 studies reported increased infertility from 12% before restorative procto-colectomy to 26% after the intervention [ 63 ]. Moreover, a retrospective study investigating seventy-one women who had undergone procto-colectomy and ileostomy for UC and CD reported a reduction from 72% to 37% in fertility after surgery [ 66 ]. On the other hand, the psychological reluctance to conceive may depend on an altered perception of reality, which leads to an unjustified fear of the hereditary transmission of IBD, congenital abnormalities, pregnancy risks, worsening of the IBD condition during the pregnancy, and medication teratogenicity [ 67 ]. Regarding IBD heritability, available data suggest only a partial influence of the genetic components on disease onset, with high chances that the child will not develop the disease (91% if only one parent is affected and 60% if both parents are affected).

Studies on IBD and pregnancy are contradictory. Some evidence suggests that conception occurring during the phase of active disease leads to a relapse of the illness in 2/3 of patients, with symptoms worsening in more than 60% of cases [ 68 ]. Moreover, the state of active disease at the time of conception could negatively affect the fetus, increasing the risk of miscarriage and reducing birth weight and pre-term birth [ 69 ]. Conversely, some studies have described a positive effect of pregnancy on IBD symptoms, especially when gestation starts during a period of disease remission. The gestation effects on IBD pathology are reported to be positive also when pregnancy starts during active disease, leading to remission in more than 70% of women with CD and more than 65% of women with UC [ 53 , 67 , 69 ]. Indeed, the intensification of symptoms during pregnancy is only transitory, and it appears during the first trimester, mainly provoked by the discontinuation of the maintenance therapy. With regard to the worsening of the IBD condition, women conceiving during illness remission have the same chance of exacerbation as non-pregnant patients with IBD [ 53 , 67 , 69 , 70 ]. Pregnancy-induced positive effects are long-term, influencing the disease symptoms over a period that may last years. Available data show a reduction in the rates of stenosis and resection and annual exacerbation rates (from 0.34 to 0.18 in UC and from 0.76 to 0.12 in CD) [ 69 , 71 ]. The reasons underlying these findings remain elusive, but they could be associated with the positive effect of pregnancy on the immune system and the beneficial role that sex hormones exert on IBD symptoms. Indeed, studies in animal models showed that the progressive increase of estrogen and progesterone throughout gestation decreased pro-inflammatory cytokine production and improved intestinal epithelial barrier function, reducing bacterial translocation and IBD activity at the end of pregnancy [ 54 , 72 ]. Despite concerns about continuing drug medication during pregnancy and breastfeeding, data indicate that, except for methotrexate, drugs used for IBD treatment are generally safe and do not increase the risk of congenital abnormalities or adverse effects on the fetus. The Toronto and ECCO consensus statements recommend continuing thiopurines, or anti-TNF alpha agent therapies during pregnancy in well-controlled women, as the treatment benefits outweigh the risks. There is still much confusion about the effect that IBD could have on pregnancy; therefore, it is of paramount importance that women affected with IBD and with the desire to conceive be addressed by proper medical counseling [ 53 ]. Compliance with treatment improves in women who receive an appropriate consultation regarding drug therapy before conception and during gestation [ 69 , 73 ]. Thus, gastroenterologists should stimulate discussion about concerns related to IBD and pregnancy, reassuring patients about treatment safety. Overall, the importance of maintaining disease remission should be emphasized for the best pregnancy outcome.

Fluctuation in ovarian hormone levels influences visceral hypersensitivity, GI transit time (via sex hormone receptors), and pain perception (via opioidergic and serotonergic systems) [ 74 , 75 ]. Puberty, pregnancy, and menopause are the three phases in a woman’s life in which sex hormones have a crucial role and influence IBD symptoms and outcomes [ 3 ]. Hormones, such as 17-beta estradiol (estrogen), prolactin, and testosterone, are considered directly involved in symptom variation, albeit molecular and cellular mechanisms involved in IBD pathogenesis are still poorly understood. Moreover, the activation of estrogen receptors expressed by epithelial cells contributes to the increase of gut permeability and the activation of humoral and cellular immunity [ 74 ]. Notably, the estrogen receptor beta (ERb) seems to have a role of paramount importance in IBD. The ERb is highly expressed in colonic epithelial cells, thereby preserving tight-junction organization, mucosal structure, and barrier function. Interestingly, its expression is markedly reduced in the colonic mucosa of CD/UC patients with active disease [ 76 ]. Upon ligand binding, ERb translocates into the nucleus and regulates the transcription of target genes [ 3 ]. In an experimental model of CD-like ileitis, Goodman et al. found that ERb protected male but not female mice. Conversely, ERb activation was associated with an anti-inflammatory effect in female but not in male UC models. The molecular mechanisms underlying ERb signaling, and, in general, intestinal inflammation may explain the gender gap observed in the UC incidence, as seen in CD [ 77 ]. The different phases of the menstrual period affect GI symptoms cyclically, and menstruation worsens GI symptoms, primarily diarrhea, in IBD women. Indeed, studies investigating the effect of IBD disease activity and medications on GI symptoms during the menstrual cycle found a correlation between disease activity and the worsening of GI symptoms [ 78 ]. Consequently, treatment of menstrual disorders with non-steroidal anti-inflammatory drugs (NSAIDs) and oral contraceptive pills (OCP) may influence the IBD course. Women affected by IBD showed a delayed onset of puberty and irregularities in menstrual function (e.g., menstrual abnormalities, oligomenorrhea, and polymenorrhea) [ 74 , 79 ]. Interestingly, alterations in the menstrual cycle can occur a year before IBD diagnosis and are favored by corticosteroids [ 80 ]. The mechanisms that evoke menstrual cycle abnormalities are yet to be clarified; possibly, the stress associated with a chronic disease, surgeries, and nutrient malabsorption could play a role. Surprisingly, symptoms improved with the increase in disease duration. Studies on the contribution of menopause and hormone replacement therapy (HRT) on IBD disease activity are few and inconsistent. Some evidence suggested that CD could anticipate menopause [ 81 ], while others found no differences between IBD women and healthy controls [ 82 ]. Thus, menopause has little or no effect on disease activity and flares. Research evaluating the association between IBD and HRT found a decrease in the risk of flares during the first two years after menopause, a phenomenon likely promoted by the anti-estrogen action known to exert inflammatory properties [ 83 ]. Conversely, a study on American women found a correlation between the use of HRT and the risk of developing UC, but not CD [ 84 ]. HRT-UC relation could be allegedly induced by the effect of estrogens on intestinal permeability, immune function, and influence on gut microbiota. Few studies have also investigated the role of OCP on IBD flare-ups. One study of 152 CD patients reported an increased risk of relapse among CD patients taking OCP [ 85 ]. In contrast, another study of 331 women aged 16–50 found no increase in the risk of relapse in patients with CD on OCP treatment [ 86 ]. In this subset, it has been speculated that the increased risk of CD in patients may be due to the effect of estrogen on venous hypercoagulability. In addition, estrogen may enhance the development of T helper 1 (Th1) and/or T helper 2 (Th2)-mediated inflammatory diseases. Finally, the modification of the gut microbiome should be addressed. The increased risk of CD in premenopausal women on OCP and the risk of increased UC in postmenopausal women on HRT could explain the differences in the hormonal milieu during each state [ 87 ].

Studies investigating the effects of medications used to treat IBD and menstrual function are inconclusive. The use of adalimumab (ADA) has been reported to be effective in restoring menstruation in a 36-year-old female with ankylosing spondylitis and premature ovarian failure [ 88 ]. However, the same drug had an adverse effect on menstrual function in a 32-year-old woman with menorrhagia and menstrual pain [ 89 ]. The use of anti-TNF-α has been investigated in patients with endometriosis, as this condition is thought to share common features with immune-mediated diseases such as IBD. There is little available data about this possible relationship. However, a trial assessing pain scores in 21 women with endometriosis randomly assigned to either infliximab or placebo found no difference between the two groups [ 90 ]. Moreover, the limited evidence between IBD surgery and menstrual function suggests that surgical procedures (i.e., bowel resection and anastomosis, and, respectively, stricturoplasty for CD and IPAA for UC) have a negative impact on menstrual function. A study evaluating menstrual abnormalities in 662 women who underwent surgery for IBD revealed that 60% of women with CD and 53% with UC experienced menstrual cycle abnormalities [ 79 ]. There is a lack of data on the effect that bowel resection and anastomosis have on the menstrual cycle, and for CD, there is a need for research investigating the role that strictureplasty could exert on menstrual function. Findings on the effect of colectomy on menstrual irregularities in UC patients showed no or minor menstrual irregularities after surgery with resolution over time [ 64 , 91 ]. Moreover, few studies suggested an association between CD and endometriosis in the ileum and colon [ 92 ]. A study including 37,661 women hospitalized for endometriosis [ 93 ] supported a link between this condition and IBD. The co-existence of endometriosis and IBD could be explained by their similar immunological features and the use of OCP to treat endometriosis. Furthermore, data on dysmenorrhea and IBD are scarce. A study investigating 44 CD patients and 66 controls concluded that dysmenorrhea together with CD are prognostic factors for global pain severity, and that patients reported higher pain scores during the menstrual cycle vs. controls [ 94 ]. The most used therapy to treat dysmenorrhea in IBD patients is nonsteroidal anti-inflammatory drugs (NSAIDs). The use of such drugs has been debated. Indeed, a study reported an increased absolute incidence of CD and UC in women exposed to NSAIDs for at least 15 days/month, suggesting that these drugs could trigger the onset of IBD [ 95 ]. However, findings on the effect of NSAIDs on IBD flares are contradictory. One study on 704 subjects found no relation between the use of NSAIDs and IBD relapse, whereas another study investigating 209 patients found a significant association between NSAIDs and early clinical relapse [ 96 ]. Overall, these results suggested a cautionary approach when using NSAIDs and avoiding them if possible. Studies assessing the effect of IBD on women’s fertility and pregnancy are summarized in Table 3 .

Psychiatric disorders and psychological distress showed a female preponderance in IBD. Self-reported quality of life questionnaires showed lower scores in females than in males [ 97 , 98 , 99 ]. A Chinese study involving more than 1000 participants of both genders suggests that the impact of CD in females is related to a lower satisfaction level of quality of care (QoC) due to disease symptoms (e.g., pain and discomfort) and depression [ 100 ]. Another study aimed at finding gender-specific concerns in 1102 Swiss IBD patients revealed that cancer risk is the primary concern for both genders. Women >40 years old were not worried about their illness but being unemployed increased their concern [ 101 ]. Fatigue, a typical symptom of IBD, seems to be more present in women than men, independently from anemia and the state of activity of the disease [ 102 , 103 , 104 , 105 ]. Moreover, sexual activity is reduced in women more than men, mainly because of their impaired sexual body image and libido after surgery [ 106 , 107 ]. However, although females appear to be more prone to psychological disorders, they are also interested in receiving information regarding depression from specialists and media [ 108 ]. Additionally, when the disease is active, women report more use of emotion-focused and problem-focused coping than men. Such behavior may depend on the traditional role of family caregivers, which is still strongly present in developed countries. In general, society has always invested women with a clear system of expectations that has distorted the real perception of their nature. However, in recent years, scientific research has begun to investigate women with a more rational and objective approach. In this light, there is a need for future studies that will accompany women’s methods of coping with various diseases in a way that “exceeds” or counters the “normative” set of expectations that has been adapted to the male methods of recovery and coping [ 109 , 110 ]. Studies evaluating psychosocial distress, emotional disturbances and impaired QoL in patients with IBD are summarized in Table 4 .

Inflammatory bowel diseases (IBD) are a heterogeneous group of chronic and relapsing intestinal diseases that consist of two main clinical phenotypes: Crohn’s disease (CD) and ulcerative colitis (UC) [ 1 ]. As in other immune-mediated diseases, gender affects the disease onset, course, and complications, including compliance with medical and surgical therapies [ 2 ]. Indeed, the female gender appears to be a promoting factor in CD onset, whereas it may exert a protective role in UC. Albeit the molecular pathways underlying these differences have not been unveiled yet, hormones and sex-specific differences in the immune system have been advocated to play a pivotal role in the onset and subsequent development of IBD [ 3 ]. This review describes the role and peculiar characteristics of the female sex in IBD. We will start by explaining how the female gender affects IBD epidemiology, phenotype, and activity; then, we will discuss clinical features, therapy, treatment adherence, and psychosocial aspects associated with IBD. Finally, we will illustrate how IBD affects women’s perceived quality of life (QoL). Altogether, our task is to provide gastroenterologists with a thorough update on gender-related IBD differences, including the management of female patients.

In this narrative review, we conducted a PubMed, EMBASE, MEDLINE, and ScienceDirect search from the inception of March 2022 to the end of August 2022 using the following search terms: “IBD” AND “female” AND “gender” OR “sex”. Literature research was carried out on the title and abstract. We also evaluated the reference list of each of the collected papers to find any other pertinent articles. The following criteria restricted the search strategy: (1) reported female-specific differences in IBD; (2) articles published in the last ten years (January 2012–August 2022); (3) material written in English; (4) full text available. The article search was carried out independently by two authors (LL and GC) who screened the titles and abstracts of the selected records. The records identified at the first step were then fully evaluated, considering the manuscript and appendices. Disagreements were resolved by consensus, and if not the case, the opinion of a third author (RDG) was considered. Non-pertinent papers or those not matching the inclusion criteria were excluded. Duplicates, papers with no original data, incomplete or with unclear outcomes were also excluded. The description of the process of study selection and the number of records found in each database are summarized in Figure 1 .

IBDs are chronic disorders with an unpredictable natural history and outcome. Gender-specific differences influence the onset, course, and therapy, as in other immune-mediated disorders, i.e., rheumatoid arthritis, scleroderma, and systemic lupus erythematosus. Moreover, unlike healthy women, females with IBD show an impaired menstrual cycle, reduced libido, and decreased sexual activities. However, although women suffering from IBD present a lower quality of life and a higher rate of psychological disturbances than men, they also show a more proactive attitude to solving their psychological problems and better coping strategies. Awareness of female-related issues in IBD presentation and progression may improve diagnostic and therapeutic strategies to aid women’s health. Gender medicine could be the correct answer to the gender-specific issues arising from IBD patients’ management by improving: (a) IBD diagnosis timing; (b) recognition of gender-specific symptoms; and (c) IBD treatment. Overall, IBD affects many sides of a woman’s health, as summarized in Figure 2 . Unveiling the plethora of complex biological mechanisms promoting the female-specific differences in IBD could foster gender-tailored treatments for IBD.