Assessing female sexual dysfunction in epidemiological studies: why is it necessary to measure both low sexual function and sexually-related distress?

Female sexual dysfunction (FSD) affects the health, relationships and quality of life of substantial numbers of women worldwide. FSD includes disorders of desire, arousal, orgasm and sexual pain. The American Psychiatric Association’s (APA) Diagnostic and Statistical Manual of Mental Disorders 4th edition (DSM-IV) stipulates that both low sexual function and sexually-related personal distress need to be present for a diagnosis of FSD. This means that only those women who are distressed by their low levels of sexual function can be classified as having FSD. Female sexual function and dysfunction need to be viewed in context, not simply as physiological phenomena occurring in isolation of other circumstances. A woman’s sexual functioning may be influenced by relationship factors, social situations, cultural influences, psychological conditions and her stage of life. For example, if a woman’s partner experiences sexual dysfunction this can affect her own sexual responses. There is evidence that when men with sexual dysfunction are successfully treated for this condition then desire, subjective arousal, lubrication and orgasmic function in their female partners also improves. Several studies have also provided evidence that the length of time a women has been in a relationship can affect her sexual function. In addition, psychological and relationship factors may influence whether she feels distressed about her own sexual functioning. In recent years, the methods used to assess FSD in epidemiological studies have come under increasing scrutiny. When assessing FSD, adhering to current definitions is crucial for consistency across studies. Appropriately validating the instruments used as outcome measures is also important because it provides essential information including how well the instrument can discriminate between women with and without clinically diagnosed FSD. A wide variety of instruments have been used to assess FSD in the past. These range from more complex scales that have undergone extensive validation studies to a simpler approach where respondents are asked a single question corresponding to each of the main types of sexual dysfunction. Certain types of FSD are particularly complex and have been conceptualised as consisting of multiple aspects of sexual functioning and dysfunction. Multi-item scales are needed where there is an underlying conceptual entity with several aspects which may not be covered by a single question. Several validated, multi-item instruments have been developed to measure the low sexual function component of FSD. Examples of these multi-item instruments include the Sexual Function Questionnaire, the Profile of Female Sexual Function and the Female Sexual Function Index. These instruments have been translated into a variety of different languages and are beginning to be more widely used in epidemiological, observational studies. The sexual distress component of FSD has attracted increasing attention in published reports. Validated measures of sexual distress have also been developed. This has created an opportunity for researchers to measure both the low sexual function and sexually-related personal distress components of FSD as stipulated by the APA. Despite this, studies using sets of simple questions that do not take sexual distress into account have been widely cited and have been highly influential in this area of research.