Prevalence of Sexual Dysfunctions: A Systemic Approach

Azita Goshtasebi1, Samira Behboudi Gandevani2, and Abbas Rahimi Foroushani3 1Department of Family Health, Mother and Child Health Research Center, Iranian Institute for Health Sciences Research, ACECR, Tehran, 2Midwifery Department, Faculty of Medicine, Tarbiat Modares University, Tehran, 3Department of Epidemiology and Biostatistics, Faculty of Public Health, Tehran, University of Medical Sciences, Tehran, Iran


Introduction
This chapter is intended to provide an evidence-based overview of the worldwide epidemiology of sexual dysfunction since the 1990s in general populations of different countries, allowing for the generalization of findings at the given population level. The descriptive and analytic literature on sexual function was identified through searching conventional databases, literature surveys and references. This chapter is organized as follows: we first review epidemiological concepts focusing on the issue of determining prevalence; then, we review the female and male sexual dysfunctions prevalence. Since only recently sexual function and sexual problems have been openly discussed in most societies and cultures (Tiefer, 2001), few epidemiologic data exist until the middle of the twentieth century. The large population-based study of normative data on female sexuality was published by Kinsey and coworkers in 1953. Recent studies, however, have presented a more accurate picture of sexual dysfunction prevalence.

The epidemiology of sexual dysfunction
Epidemiology is a scientific study of the distribution and determinants of diseases in populations. Epidemiological data are the basis for assessing the overall impact of a condition on a given society (Prins et al., 2002). These data are needed for public health systems in order to recognize the impact of the studied condition in the population and organize screening, diagnostic and treatment strategies .One of the basic epidemiological measures of outcome occurrence is prevalence which is defined as the proportion of a population exhibiting a health condition during a specific time interval (Simons et al. 2001). Moreover, prevalence is characterized by the proportion of a given population which has the condition at a given time. While prevalence can refer to any time period, researchers typically distinguish among point, period and lifetime prevalence. An important conceptual issue is to define sexual dysfunction which is used when it is clinically diagnosed. Another

Prevalence of female sexual dysfunction
Despite increasing scientist interest in female sexual difficulty and dysfunction, the true prevalence of female sexual dysfunctions (FSD) in the general population remains a contentious issue. One reason is the great deal of variation in the published prevalence estimates of female sexual difficulties/ dysfunctions. This variation may be due, in part, to real differences among populations, and the way FSD is measured (Lindau et al,. 2007). Lack of standardization of outcome measures is an important issue in the FSD literature which has been raised by previous authors. Also, different time frames have influenced the prevalence rate. If the period of study increases, prevalence increases, too (Mercer et al,. 2003).
The prevalence of female sexual dysfunctions, as reported in reasonably valid descriptive investigations, are showed in Tables 1-4. There are currently four international data sets with some information about women's sexual problem; five studies in Africa, eleven studies in Asia, eleven studies in Europe and eleven studies in America. Table 1 show that the low level of sexual desire prevails in 11.2%-66.4% of subjects in different age strata. This indicates that sexual arousal dysfunction with this large variation is a worldwide problem at different ages. In several countries, there is a clear decline in sexual interest at advanced ages.

Arousal/lubrication dysorders
There are genital and psychological aspects for arousal disorders. But, they are not explicitly separated. Insufficient lubrication generally appears in almost 49% of women. Also, it seems that this problem is more common in two ends of reproductive ages.

Orgasm dysorders
The prevalence of orgasmic dysfunction varies considerably within and between different geographic areas and some researchers believe that this problem may or may not be agedependent. The highest report belongs to India in which more than 86% of women report this problem. Also, this problem is very common among African women.

Dyspareunia
The manifest of genital pain during intercourse has been also reported by a large number of women all over the world. Overall, high prevalence of about 64% has been found in Asia and Africa. Vaginismus is another painful condition during intercourse with high prevalence in Asia.
But, it appears that there is clear lack of investigation of this problem in the world.

Prevalence of male sexual dysfunction
Male sexual dysfunction includes erectile dysfunction (ED), ejaculation disorders, orgasmic dysfunctions and disorders of sexual interest/desire. Epidemiologic studies have supported the high prevalence of male sexual dysfunction worldwide; however, the data are limited. Many of the epidemiologic studies are old and related to poor methodology. In this chapter, we reviewed 29 multiethnic studies about these problems. Tables 1-4 show validated studies on the prevalence of male sexual dysfunction.

Erectile dysfunction (ED)
Erectile dysfunction (ED) is defined as the consistent or recurrent inability of a man to attain and/or maintain penile erection sufficiently for a sexual activity. A 3-month minimum duration is accepted for the establishment of the diagnosis. Several studies have provided data on the prevalence of ED. The prevalence of ED on a worldwide basis has a great deal of variation around 9%-69%. And, there is a clear increase of this disorder at older ages. In all studies, ED has a rather high rate from 20% to 40% for the ages 60 to 69 years old, some increasing after the age of 65 years old.

Ejaculation disorders
Ejaculation disorders include early ejaculation, delayed ejaculation and anejaculation. The term early ejaculation is used to replace premature ejaculation, a term considered relatively inaccurate and pejorative. Early ejaculation is the ejaculation that occurs sooner than desired, either before or shortly after penetration, over which the sufferer has minimal or no control. Like all or most other dysfunctions, this is primarily a self-reported diagnosis. Delayed ejaculation is the undue delay in reaching a climax during sexual activity. Anejaculation is the absence of ejaculation during orgasm (Althof et al, 2006). The major problem in assessing the prevalence of early ejaculation is lack of an accurate (validated) definition. It can be defined by time of ejaculation, in the context of the sufferer's or partner's satisfaction, the number of penile thrusts after intromission or even in the context of the amount of sexual stimulation. Similarly, there is lack of definition for the delayed ejaculation. The highest prevalence rate of 31% (men aged 18-59 years old) was given by the NHSLS study in the United States (Laumann et al., 1999). In the sub-groups aged 18 to 29, 30 to 39, 40 to 49 and 50 to 59 years old, the prevalence was 30%, 32%, 28% and 55%, respectively. These high prevalence rates may be a result of the dichotomous scale (yes/no) in a single question asking whether the ejaculation occurred too early or not.

Orgasmic dysfunction
Orgasmic dysfunction is the inability in achieving orgasm, markedly diminished intensity of orgasmic sensations or marked delay of orgasm during conscious sexual activity. There is a self-report of high sexual arousal/excitement in this disorder. Prevalence data on orgasmic dysfunction are scarce and report 5%-33% of all men in the world. One simple reason explaining the difficulty of assessing the prevalence of orgasmic dysfunction is that some men may be unable to distinguish between ejaculation and orgasm.

Sexual interest/desire dysfunctions
Sexual interest/desire dysfunctions are diminished or no feelings of sexual interest or desire, no sexual thoughts or fantasies and lack of responsive desire. This problem has been neglected in epidemiologic studies to some extent; but it is quite commonly seen in clinical practices. The prevalence rate of sexual interest disorders is 11%-28% around the world. The highest prevalence rate of sexual interest disorders was reported in a study conducted in Asia in men aged 40 to 80 years old. It seems that there is not any pronounced age effect on this problem. However, more research would shed more light on this issue.

Conclusions
Existing epidemiologic data on sexual dysfunction support high prevalence of these problems worldwide. However, the data are limited and the prevalence data on male sexual dysfunction, except for ED, are too limited. Widely accepted definitions of disorders and scales are primary prerequisites to make prevalence comparisons possible and describe the severity of the problem.

Acknowledgement
Authors would like to thank Ms Zahra Sehat for searching and organizing papers. Sexual dysfunctions have recently recognized as one of the major public health problems. This book enhances our scientific understanding of sexual function and dysfunction from different perspectives. It presents evidence-based interventions for sexual dysfunctions in difficult medical situations such as cancer, and gives a valuable overview of recent experimental researches on the topic. Published in collaboration with InTech -Open Access Publisher, this imperative work will be a practical resource for health care providers and researchers who are involved in the study of sexual health.