In 1998, Viagra® (Sildenafil citrate) entered the U.S. market and revolutionized sexual function in men, opening up a whole new era in medicine. Although such a rapid revolution in women has not occurred, female sexual function is progressively gaining prioritization in health care. This is evident by the approval of new medications by the U.S. Food and Drug Administration. Two medications, Addyi™ (Flibanserin) and Vyleesi™ (Bremelanotide), both work centrally in the brain and have been shown to increase sexual desire and the number of satisfactory sexual events in premenopausal women with hypoactive sexual desire disorder.¹ Other medications like the selective estrogen modulator Osphena® (ospemifene), dehydroepiandrosterone in the form of Intrarosa® (prasterone) and vaginal estrogen are all used to treat vaginal dryness and painful intercourse.² The female sexual response and treatment outcomes are more challenging to assess than in men due to differences in anatomy and physiology, the nature of the female sexual response, psychological factors, as well as the influence of social, cultural and educational background. The significant placebo effect found in trials of sexual dysfunction treatment (40% in women vs 10% in men) supports the complexity of the sexual response in women and the need for more research in this area.³

Significant advances in knowledge of the female sexual response cycle and treatment options for female sexual dysfunction (FSD) happened during the end of the 20th century and beginning of the 21st century. Similar to the male sexual response cycle, the female sexual response consists of 4 phases: desire, arousal, orgasm and resolution.⁴ The desire stage involves an interest in being engaged in sexual activity, usually due to any internal and/or external stimuli. If stimulation continues, the arousal phase will manifest with physiological changes that are happening in the body, such as an increase in heart rate, body temperature, as well as vaginal lubrication. The peak of sexual response cycle is orgasm, which is characterized by involuntary vaginal wall, uterine, and pelvic floor contractions, genital vasocongestion, and a general state of euphoria. Afterwards, a return to the baseline state happens in the resolution phase. These phases are dependent upon each other to ensure the success of each component. For example, orgasmic difficulties could come from insufficient arousal, or low desire could contribute to suboptimal arousal, etc.⁵

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), FSD refers to difficulties in the sexual response cycle that prevent satisfaction from sexual activity.^6,7 Causes of FSD are classified as either female sexual interest/arousal disorder, female orgasmic disorder and genitopelvic pain/penetration disorder, substance/medication-induced sexual dysfunction, and not otherwise specified. Dysfunction could happen in each of these domains at some point in a woman’s life. FSD does not require treatment unless it causes distress and it persists for a minimum of 6 months. It is important to rule out any psychological causes (including mental or relationship issues), general health issues (obesity, hypertension, multiple sclerosis) and substance abuse.

Subjective assessment of sexual dysfunction and effect of treatment are based on a woman’s own perception. Diaries and event logs have been widely used in clinical trials to evaluate male sexual dysfunction and later were adapted for FSD. To unify responses and to quantify outcomes, multiple questionnaires have been developed. A widely used questionnaire is the Female Sexual Function Index (FSFI), which consists of 19 questions and assesses 4 domains: desire, arousal, orgasm and sexual pain.⁸ The total score ranges from 0 to 36, with higher scores indicating better sexual function.⁹ A total score below 26 indicates clinical FSD.¹⁰ The shorter version of the FSFI contains 9 questions (FSFI-9). It has been psychometrically tested and compared to the original FSFI, and was found to be valid and sensitive.¹¹ The FSFI is considered the female equivalent of the International Index of Erectile Function (IIEF).¹² Similar to the IIEF, the FSFI does not capture sexual function in sexually inactive women. However, it has good reliability and validity.

Another questionnaire used for outcomes assessment is the Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire (PISQ). This validated questionnaire has 3 versions. The Pelvic Organ Prolapse/Urinary Incontinence Sexual Questionnaire International Urogynecological Association (IUGA) Revised (PISQ-IR) contains 20 questions and accounts for the status of sexual activity in women with urinary incontinence (UI) and pelvic organ prolapse (POP). Sexually active women answer 21 questions in 6 domains, while sexually inactive women answer 12 questions in 4 domains. Another version of the PISQ is the PISQ-12. While it includes questions related to pelvic floor issues (incontinence of urine/stool), it is not suitable for sexually inactive women. The recently developed PISQ-9 questionnaire does not contain condition-specific questions and is suitable for women without pelvic floor dysfunction. However, it does not measure sexual function in sexually inactive women.¹³

According to the Pelvic Floor Disorder Consortium (PFDC), the PISQ-IR is the recommended tool for assessment of sexual function in women with pelvic floor disorders. The consortium recommended the FSFI for assessment of sexual function in women without pelvic floor disorders, although in everyday practice when assessment of sexual function is a secondary end-point and brevity is a priority, the FSFI-9 is recommended.^11,14

All of the above questionnaires are well standardized, inexpensive, and easy to administer and score. However, validity is affected by many factors including ethnic, cultural and educational backgrounds. Unfortunately, the validation of questionnaires for assessment of treatment outcomes is sparse. In fact, we previously found that 54% of women given the FSFI and the PISQ-IR questionnaires wrote in the margins of questionnaires in order to better convey their sexual experience. This reminds us again that women are more complex than the available questionnaires can measure. Honest discussion and direct feedback remain vital to the subjective assessment and the best tailored treatment of female sexual function.