Paul Yong

Associate Professor

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Endometriosis affects one in ten women, and is a common cause of pelvic pain and infertility. It is a condition where tissue from inside the womb, grows outside the womb, typically elsewhere inside the abdomen. In particular, endometriosis causes pelvic pain with intercourse (deep dyspareunia), which can have a devastating impact on women’s quality-of-life and relationships.

The focus of my research is on how endometriosis causes deep dyspareunia. I am investigating the genetic, cellular, nervous system, and psychological factors that lead to pain with intercourse in endometriosis. The goal is to identify the ideal treatments to reduce pain and improve sexual function in endometriosis.

Great Supervisor Week Mentions

Each year graduate students are encouraged to give kudos to their supervisors through social media and our website as part of #GreatSupervisorWeek. Below are students who mentioned this supervisor since the initiative was started in 2017.


Even before being my supervisor he was an exceptional role model in work ethics and research methods. Most importantly, he was very supportive and enthusiastic about my progress academically and professionally. He made sure that I'm being supported through each step of the way and to regain my self worth and confidence. He is truly a remarkable supervisor.

Najla Alsowayan (2019)


I am grateful for Dr. Yong endless support. Big thanks and much appreciation. He always makes time in his busy schedule for his students.

Fahad Alotaibi (2019)


So grateful to have such a brilliant, supportive, and encouraging mentor/supervisor! Thank you, Dr. Paul Yong for your patience and guidance over the last couple years. I am looking forward to learning more from you during my PhD. #GreatSupervisor #UBC @PelvicPainEndo


I'm so lucky to be supervised by two amazing researchers - Happy Supervisor Appreciation Week to Dr. Susan Cox and Dr. Paul Yong @ubcspph @womensresearch @PelvicPainEndo #GreatSupervisor #UBC


Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2021)
Interleukin 1-beta, plasminogen activator system, and nerve growth factor in endometriosis associated deep dyspareunia (2020)

No abstract available.

Master's Student Supervision (2010 - 2020)
Outcomes following surgical management of pelvic pain: a prospective cohort study (2020)

Endometriosis is a chronic, estrogen-mediated inflammatory condition associated with chronic pelvic pain and infertility. The condition affects up to 10% of reproductive aged women and is associated with significant impacts on quality of life, loss of productivity, and social isolation. Surgical intervention has been identified as an important tool in treatment of endometriosis, but the factors associated with treatment response are not clearly defined. Our current study aimed to address these issues by determining the impact of type of surgery, histology, and stage of endometriosis on surgical outcomes. We then evaluated whether conservative surgery for superficial peritoneal endometriosis resulted in positive impacts on pain and quality of life. Finally, we determined whether the characteristics of women undergoing hysterectomies before the age of 40 were different from those of women undergoing hysterectomies at age 40 or older and compared their surgical outcomes by age category. The first part of the thesis demonstrated that surgery was associated with improvement in all surgical outcomes regardless of type of surgery. Women undergoing hysterectomies demonstrated worse baseline quality of life scores but showed greater improvement in outcomes compared to conservative surgery. Stage and histology had little influence on outcomes. For the second part of our study, we found that surgery for superficial peritoneal endometriosis was associated with improvement in all outcomes except for superficial dyspareunia. Finally, the third part of study demonstrated that younger women undergoing hysterectomies tended to have earlier experiences of pain and increased likelihood of having comorbid conditions associated with central sensitization. Women
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Comprehensive evaluation of response and failure of medical treatment in patients with endometriosis-associated chronic pelvic pain (2019)

Introduction: Endometriosis is a common gynecological condition affecting 6-10% of women of reproductive age that produces significant morbidity and constitutes a substantial burden on health care systems. Endometriosis is one of the main causes of pelvic pain as it has been estimated that 33% of patients with chronic pelvic pain have endometriosis. Several medical and surgical approaches are available for the management of endometriosis.Suppressive hormonal treatments are generally considered safe and commonly prescribed, however the desired effect of pain relief is not achieved in all patients. Less attention is paid to the reasons for discontinuation and risk factors associated with it. Identifying the proportion of patients who do not benefit from these medications and the risk factors will aid in patient counseling for pain management. In this thesis, I am evaluating patients that did not respond to the first and second line medical treatment of endometriosis.Methods: This cohort included 1440 patients of reproductive age that had confirmed or clinical suspicion of endometriosis. Through an online questionnaire, we asked these patients if they have ever used each hormonal medication to treat their pelvic pain and, if the answer was yes, if the treatment did not help or whether they discontinued due to side effects.Results: In this cohort, 58.3% (839/1440) reported prior use of cyclic hormonal contraceptives, while 42.4% (611/1440) reported prior use of continuous hormonal contraceptives. For progestins, there were 24% (344/1440) patients who used levonorgestrel intrauterine device and 20.2% (287/1440) who used dienogest. Patients who reported ineffectiveness of any hormonal treatment or discontinuation due to side-effects were younger, had higher pain severity, worse quality of life, more non-gynecological contributors to pain, and greater psychological comorbidities.Conclusion: My results highlight the importance of further studying non-responders to hormonal therapy. Prospective longitudinal studies are needed to confirm these findings and further classify the side-effects experienced by patients. Moreover, additional details on treatment inefficacy are required to identify patients that are truly non-responsive versus patients who are not adherent to mediation regimens or have financial difficulties with medication costs.

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Dyspareunia uncovered: a mixed method exploration of the neglected symptom of endometriosis (2019)

The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.

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Genome-wide DNA methylation and imprinted gene analysis in babies conceived by ART (2019)

Assisted reproductive technologies (ARTs) are associated with a number of adverse pregnancy, neonatal, and long-term outcomes. One plausible explanation is that ART procedures may be causing alterations in epigenetic mechanisms, including the regulation of imprinted genes, that persist during development. Therefore, I investigated gene expression of the imprinted genes PLAGL1, CDKN1C, KCNQ1OT1, and H19 in cord blood from 24 IVF, 18 ICSI, 9 IUI, and 26 naturally conceived babies as well as genome-wide DNA methylation using Illumina’s EPIC methylation array in cord blood from 10 IVF, 9 ICSI, and 10 naturally conceived babies. All the samples were procured from healthy newborn singletons. No differences in the gene expression of the imprinted genes were observed across conception modes. The genome-wide DNA methylation analysis revealed an overall stability of DNA methylation following ART; however, a small number of CpG sites exhibited hypervariability in the ICSI (47 CpG sites) and the IVF (4 CpG sites) groups. Furthermore, the mCSEA method for detecting DMRs revealed 101 promoter associated DMRs in the ICSI group and 101 promoter associated DMRs in the IVF group. 35 DMRs overlapped between the ICSI and IVF groups, suggesting some regions may be susceptible to DNA methylation alterations following ART. Four imprinted gene DMRs were also found to overlap DMRs between conception modes. Overall this analysis revealed that a small number of genomic regions may be impacted by ART. These regions may be significant as genes associated with neurodevelopmental disorders, intrauterine programming of adult onset obesity, and male infertility were observed to be altered in both the IVF and ICSI groups. Although validation of these regions is required, this analysis provides support for ART impacting DNA methylation that persists to birth in genes related to adverse outcomes and mediating transmission of DNA methylation alterations from infertile parents to babies.

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Central sensitization in endometriosis-associated deep dyspareunia (2018)

Endometriosis affects 10% of reproductive-aged women and is the presence of ectopic endometrial glands and stroma. It is associated with different types of pain, such as dysmenorrhea, dyschezia, and deep dyspareunia. Deep dyspareunia affects approximately 50% of women with endometriosis. Previous research has suggested that, in addition to disease-specific factors (e.g., Stage), other factors such as comorbid conditions or central sensitization may also play a role in the etiology of deep dyspareunia. The thesis objective is to provide evidence for the role of these other factors in the etiology of deep dyspareunia in endometriosis. I propose that bladder/pelvic floor tenderness and painful bladder syndrome (PBS) are associated with an increased severity of deep dyspareunia in women with endometriosis, and that these factors may be related to central sensitization. In Aim 1, using data from a prospective registry, I found that bladder/pelvic floor tenderness (assess by physical exam) and PBS (diagnosed using established criteria) were independently associated with severity of deep dyspareunia in women with both Stage I/II endometriosis (AOR=1.94, 95% CI 1.11-3.38, p=0.019; AOR=1.99, 95% CI 1.15-3.44, p=0.013; respectively) and Stage III/IV (AOR=2.51, 95% CI 1.25-5.02, p=0.01; AOR=1.90, 95% CI 1.01-3.57, p=0.048; respectively). In Aim 2, by prospectively recruiting patients and measuring their pain-pressure thresholds (PPT), I determined that PPT at extra-pelvic sites were significantly associated with bladder/pelvic floor tenderness in women with endometriosis (t=2.9, p=0.007; t=2.3, p=0.029; respectively). In contrast, there was no association between PPT and PBS.In conclusion, I found that bladder/pelvic floor tenderness and PBS were associated with greater severity of deep dyspareunia, regardless of endometriosis stage. I also found evidence that bladder/pelvic floor tenderness is associated with lower PPT in women with endometriosis, which may indicate the presence of central sensitization. In contrast, PBS was not associated with changes in PPT, and thus may arise in endometriosis through mechanisms other than central sensitization. My findings point to a role for central sensitization, manifesting as bladder/pelvic floor tenderness, in some women with endometriosis-associated deep dyspareunia. Further research is needed to confirm these findings, and to incorporate measures of central sensitization into the clinical management of endometriosis.

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Plasminogen Activator Inhibitor-1 in Endometriosis (2017)

Endometriosis is a disease that affects almost 10% of reproductive-age women, where 50 % of these women have pelvic pain with sexual intercourse. Deep endometriosis is defined as an endometriotic lesion penetrating to a depth of 5 mm or more, and is characterized by both fibrosis (forming nodules) and invasion (into structures such as the colon). Other groups have found that increased plasminogen activator inhibitor-1 (PAI-1) or (SERPINE1) expression was associated with fibrosis and tumor invasion. In addition, a previous study found that the SERPINE1 4G allele (and thus increased gene expression) was associated with increased pain in women with endometriosis, and other work suggested that SERPINE1 may be implicated in local neurogenesis. The objective of this thesis is to determine whether PAI-1 expression is associated with a) deep infiltrating endometriosis; and b) deep dyspareunia. We propose that increased PAI-1 expression will be associated with deep infiltrating endometriosis, and increased pain in endometriosis via an increase in local nerve fibers. We utilized immunohistochemical analysis using a validated PAI-1 antibody. In the first cohort, we examined PAI-1 expression in deep infiltrating endometriosis and compared to endometrioma, superficial endometriosis, and eutopic endometrium. In the second cohort, we examined PAI-1 expression in cul-de-sac endometriosis from women with or without deep dyspareunia. We found higher expression of PAI-1 in deep infiltrating endometriosis (n = 10) compared to superficial endometriosis (n = 10) (p = 0.031) and eutopic endometrium (n = 10) (p = 0.002). In the second cohort, we found lower expression of PAI-1 in women with more severe deep dyspareunia (r = - 0.352, n =35, p = 0.038). However, there was no association between PAI-1 expression and local nerve bundle density. In conclusion, we observed higher PAI-1 expression in deep infiltrating endometriosis, but lower PAI-1 expression in endometriosis from women with deep dyspareunia. Further research is needed to clarify the complexities of PAI-1 expression in endometriosis.

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