**2. 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 Sexual Dysfunctions: A Systemic Approach 5

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

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

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

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

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

*Vaginismus* is another painful condition during intercourse with high prevalence in Asia.

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

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

But, it appears that there is clear lack of investigation of this problem in the world.

in Asia, eleven studies in Europe and eleven studies in America.

that this problem is more common in two ends of reproductive ages.

this problem. Also, this problem is very common among African women.

**3.1 Sexual interest/desire dysorders** 

**3.2 Arousal/lubrication dysorders** 

**4. Prevalence of male sexual dysfunction** 

on the prevalence of male sexual dysfunction.

**4.1 Erectile dysfunction (ED)** 

increasing after the age of 65 years old.

interest at advanced ages.

**3.3 Orgasm dysorders** 

**3.4 Dyspareunia** 

and Africa.

issue is to select the study sample. Community-based samples are the most appropriate ones which define the potential number of patients sustaining the disorder/condition who might benefit from treatment. The study sample must be a representative of the studied population in terms of social, cultural and health status. And, the last one is to select the tools used for screening.

In this chapter, the criterion was the prevalence estimate for general populations, which included a representative sample of community with overall methodological quality. The internal validity of the study was assessed by data collection procedures, measurement instruments, defining health conditions and informative content of reported prevalence. External validity was assessed by the generalizability of the study and source of population, sampling, eligibility of criteria and response rate (Tsai et al, 2011).

The second important issue is that sexual dysfunction may be best conceptualized as the global inhibition of sexual response due to interpersonal factors (Hartmann et al, 2002) because many cases of sexual dysfunction can be regarded as the adaption to sexual relationship problems. In other words, sexual dysfunction must be seen in a multi-faceted socio-psycho-biologic context. Therefore, there are different scales for defining and classifying sexual dysfunction including the American Psychiatric Association's Diagnosis and Statistical Manual for Mental Disorder, 4th text revision (DSM-III or IV-TR), the World Health Organization's International Classification of Diagnosis (ICD-10), Profile of Female Sexual Function(PFSF), Female Sexual Function Index (FSFI), Golombok Rust Inventory of Sexual Satisfaction (GRISS), International Index of Erectile Function (IIEF), Sexual Function Questionnaire (SFQ) and other researcher-made validated questionnaires . Clearly, the type of applied definition affects the prevalence estimate of sexual problems. Although the database in both groups is rapidly growing, in this chapter, we tried to include all the recent studies of the field.

We focused on epidemiologic studies on sexual problems, sexual disorders or sexual distress which have estimated prevalence of one or more sexual problems for general populations in the world. Thus, we excluded studies with a small sample size and studies in special populations like specific health conditions.

In this review, we searched MEDLINE, SCIENCEDIRECT, PUBMED, GOOGLE SCHOLAR, JSTORE and JSTORE PROQUEST using the following key words: epidemiology, prevalence plus sexual dysfunction, sexual function disturbance, sexual disorder, dyspareunia, vaginismus, anorgasmia, lack of lubrication, sexual arousal, sexual desire, hypoactive sexual desire disorder, sexual aversion disorder, orgasmic disorder, erectile dysfunction, early ejaculation and premature ejaculation.
