The SHR is a non-mandatory quality register that is concerned with groin hernia repair in adults. It was established in 1992 with only eight hospitals being aligned in the beginning. The objective was to study and analyse groin hernia repairs in Sweden and stimulate improvement at participating units by comparing local outcomes with those from the rest of the nation. Today, some 90 units participate, and more than 90% of all groin hernia operations performed in Sweden are registered with the SHR, which has created a national database of more than 400,000 operations. Procedures are recorded prospectively, and patients are identified by their personal identity number, which is unique for each citizen in Sweden [6]. Patients are followed from operation until reoperation, death or emigration. SHR is linked with the Swedish population register, which allows more accurate follow-up times.

Many variables have been unchanged over the years, but others have been added, and a few have been discarded. Data registered includes patient and hernia characteristics (e.g., BMI, smoking status, comorbidity, hernia anatomy, size of the hernia defect, type of hernia, etc.), technical details (method of repair and anaesthesia, use of mesh, type of mesh, fixation) and complications occurring within 30 days (including severity and need for readmission or reoperation). Reoperations for recurrence, infection or pain are included.

In addition, between 2012 and 2018, a pain questionnaire assessing patient-reported outcome measures (PROMs) was sent out 1 year after surgery to all patients that had undergone a groin hernia repair in a unit participating in the SHR. The distributed questions were collected with a 70% response rate, which is unusual for national cohorts. The short-form PROMs questionnaire included one question concerning patient satisfaction and one from the Inguinal Pain Questionnaire (IPQ) assessing chronic pain in the groin following a groin hernia repair [7]. A short-form questionnaire has been shown to be exchangeable to the longer original version of IPQ [8]. The intensity of the pain is assessed using a 7-step fixed-rate scale with steps operationally linked to pain behaviour or pain descriptors. Responses that indicate that the pain cannot be ignored and affects daily activities are regarded as moderate to severe pain. The PROM pain question and possible answers are provided in Supplementary Appendix S1.

The SHR employs a standardised annual validation of registered data, where 10% of the aligned units are audited by external evaluators. The validity of the register has been studied with a finding of 98% correct variables and a 97% cover rate for procedures in the participating units, making it a register with high validity [9].

A review was conducted on previously published studies based upon data from the Swedish Hernia Register between 1 January 1992 and 30 April 2023. PubMed and Embase were searched for studies based on data from the Swedish Hernia Register, applying the search string “‘hernia’ AND (‘Swedish Hernia Register’ OR ‘Swedish Hernia Registry’)”. Conference abstracts were disregarded. These searches were checked against a list of studies kept by the SHR. Any additional studies found there were also identified and accessed by online search. Abstracts were read by all authors. Only studies specifying results for the female gender were included in the review.

Recent data and figures were adopted from the 2022 annual report, and information from the SHR website [1, 10]. Data for 1992–2022 is presented because of its historical value. Data from a more modern period, 2012–2022, is presented separately, also coinciding fairly well with the introduction of national treatment recommendations for groin hernia from the National Board of Health and Welfare in 2011 [11].

In Sweden, approximately 16,000 groin hernia operations are registered annually in the SHR, except for 2020 due to the COVID-19 pandemic, during which the amount decreased to 12,689 operations [10]. In 2021, the number of registered operations increased again. Gender data has been reported in the SHR since the beginning. Cumulative demographic characteristics of female groin hernia repairs in the SHR in the years 1992–2022 and 2012–2022 are presented in Tables 1, 2. Developments and trends in female groin hernia surgery in the SHR can also be followed by looking at changes over time between 1992 and 2022 in Figures 1–5.

The cumulative percentage of women who underwent emergency repair for their groin hernias was almost triple that of men (14.4% vs. 5.3%) during the 1992–2022 period. The change over time is illustrated in Figure 4. Studies from the SHR have consistently shown that groin hernia repairs in women more often are carried out as an emergency then in men [15, 16].

Emergency surgery is associated with significantly increased mortality [17, 18]. In 2007, data from the SHR was merged with that from the death register and the standardised mortality ratio was calculated using death statistics in Sweden. 107,838 hernia repairs, including 8,182 repairs in women, were analysed. After emergency surgery, women had a higher risk of mortality than the background population, with a standardised mortality ratio of 20.49 (95% CI 13.26–30.25) if bowel resection was undertaken and one of 5.36 (95% CI 3.47–7.92) if no bowel resection was needed [18]. When the medical records of patients who had died within 30 days of hernia repair were examined, only 37% of patients with signs of bowel obstruction had had a documented groin examination upon admittance, and women were significantly less likely to undergo a groin examination compared to men [19].

A protective impact on risk for postoperative complications within 30 days of operation was seen in a study in 2012 [20]. When adverse events were studied later, and merged data from the SHR with data from the national patient register, the male gender was found to be associated with an increased risk of both cardiovascular events and intraoperative complications [21]. A study from 2002 found that although women had neither more registered nor more self-perceived adverse events, they sought healthcare advice regarding their perceived complications more often (in 75% of cases versus 48% for men, p = 0.003) in a study cohort from 2002 [22]. A tendency, although not statistically significant, for women to file damage claims more often (OR 1.62, 95% CI 0.98–2.71, p = 0.06) after groin hernia surgery was found by Nordin et al., while they were investigating damage claims between 2008 and 2010 [23]. Women (and men) who were lean (BMI < 20 kg/m²) or overweight (BMI > 25 kg/m²) had an increased risk of postoperative complications within 30 days of a groin hernia repair [12].

The first study using SHR data that focused on femoral hernias was published in 1999, but it included few comparisons between men and women [24]. A larger cohort of femoral hernia repairs was studied by Dahlstrand et al., who analysed 3,980 femoral repairs with a focus on recurrence, mortality and emergency operations [16]. The study demonstrated that 22.8% of groin hernia procedures in women were due to femoral hernias, whereas the corresponding proportion for men was 1.1%. Emergency procedures were more common in women, constituting 40.6% of their repairs (22.8% for men, p < 0.001). A study where 442 femoral hernia patients with emergency repairs retrospectively reported whether they had sought medical advice regarding their hernia and/or known about it prior to their surgery indicated that only 46.7% of the patients were aware of their hernias, while 31.3% denied symptoms from the groin more than 2 weeks before surgery. There were no differences between men and women in terms of symptoms [25].

Each hernia operation is followed in the SHR until either reoperation of the same groin or the patient’s death. This allows the probability of reoperation due to recurrence to be calculated as a function of the time after a hernia operation. Before 2005, gender had not been assessed as a risk factor for recurrence in studies from the SHR. In 2005, 6,895 prospectively registered groin hernia operations in women were studied specifically. Koch et al. found that women had a significantly increased risk of having a reoperation because of a recurrence (HR 1.30, 95% CI 1.13–1.49) [15]. They also found that Lichtenstein, the repair method with the lowest risk of reoperation in men, was associated with the highest risk for reoperation in women. Furthermore, femoral hernia was diagnosed in 41.6% of reoperations after hernias originally classified as inguinal hernias. A more recent study of more than 17,000 repairs in women confirmed the results and reported that by far, endo-laparoscopic repair was the method associated with the least risk for reoperation in women but, doubled the risk for reoperation due to recurrence in men [26]. Koch et al. suggested that surgeons missed femoral hernias when open anterior mesh techniques were used. Thus, the 2011 national guidelines recommended a laparoscopic posterior mesh repair in all groin hernias in women due to the superior ability to visualise all groin hernia orifices during the procedure. The method of choice has changed for women in Sweden since then (Figure 3).

Today, the female gender is no longer associated with an increased risk of reoperation in Sweden. Figure 5 indicates the cumulative risk of reoperation for recurrence following a primary groin hernia repair with open versus endo-laparoscopic surgery. In Cox regression analysis regarding reoperation for recurrence following open or endo-laparoscopic surgery for primary groin hernia repair 2013–2022, stratified by gender, endo-laparoscopic repair was associated with a lower risk for reoperation than open repair for women [hazard ratio (HR) 0.303; 95% CI 0.232–0.396; p < 0.001] but a higher risk for men (HR 1.728; 95% CI 1.601–1.864; p < 0.001) [10]. The difference in the effectiveness of totally extra-peritoneal (TEP) groin hernia repair for the different genders was also demonstrated in a study of TEP procedures registered in the SHR 2005–2013 [27]. The authors found that women had a lower risk for reoperation due to recurrence (HR 0.39, 95% CI 0.26–0.59) compared to men.

One of the most important adverse events following groin hernia surgery is chronic pain. A total of 4,021 women with unilateral primary groin hernia repair answered the 1 year follow-up questionnaire for patient-reported outcomes that was sent out by the SHR between 2012 and 2018. A significantly larger proportion of women than men reported suffering from chronic pain; 18.4% of women versus 15.2% of men [28]. In the same study, women also reported severe pain more frequently. Moreover, TEP groin hernia repair was associated with less chronic pain in men but not in women. However, a similar trend was indicated for women. Bjurström et al. investigated 955 women and 1,129 men with repairs who had completed the PROM during the same time period [29]. The authors found that the differences in pain between genders described at 1 year after surgery were still present 5 years after surgery when assessed with the Brief Pain Inventory [30]. Reoperation due to pain after groin hernia repair is rare, with a frequency of 0.13% in the SHR, but women have been found to be at greater risk (HR 2.13, 95% CI 1.41–3.21) [31].

The association between sleep disturbances and chronic pain after groin hernia repair has been investigated, with a specific focus on differences between the genders [29]. Retrospectively, women reported persistent sleep problems prior to surgery more often than men. Preoperative sleep difficulties were a significant risk factor for chronic pain both 1 year after surgery and in the long-term follow-up.

Chronic pain has also been studied for the subpopulation with femoral hernia repairs. Pain was demonstrated to be as common as after inguinal repairs in a study that investigated 1,461 patients who completed the IPQ at a median follow-up time of 4.7 years after surgery. Women constituted 72% of the 1,461 respondents; no differences between the genders were seen in terms of pain, with 5.5% of patients reporting pain of at least moderately severe intensity [32].