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Keywords:

  • Sexual Dysfunctions;
  • Epidemiology;
  • Prevalence;
  • Incidence;
  • Nosology

ABSTRACT

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

Introduction.  Epidemiology can be defined as the population study of the occurrence of health and disease. The knowledge of the rates of occurrence of sexual dysfunctions and the primary risk factors for these conditions is very important to assist in assessing the risk and planning treatment and prevention programs in sexual medicine.

Aim.  Review modern studies of the prevalence and incidence of sexual dysfunction in an effort to establish a consensus concerning the frequency of occurrence of these conditions, and review the strengths and liabilities of design methodology in the field.

Main Outcome Measure.  Review of peer-reviewed literature.

Results.  The findings suggest that sexual dysfunctions are highly prevalent in our society worldwide, and that the occurrence of sexual dysfunctions increases directly with age for both men and women. There is also a strong support for the finding that although the frequency of symptoms increases with age, personal distress about those symptoms appears to diminish as individuals become older. An additional uniform result was that specific medical conditions and health behaviors represent major risk factors for sexual disorders, and that many of these health conditions also have a strong positive relationship with age.

Conclusions.  Progress has been made concerning both the number and quality of epidemiologic prevalence studies in sexual medicine; however, there is a paucity of studies of the incidence of these conditions. Because reliable incidence data are critical for prevention and treatment planning, the design and execution of the incidence trials should become a high priority for the field. In addition, repeated calls for the development of a new systematic and integrated diagnostic system in sexual medicine were also evident, because of the perception by many that the imprecision of our current diagnostic system represents the “rate-limiting step” for the epidemiology of the field. The review suggests that although much has been accomplished in the past 15–20 years, much remains to be done. DeRogatis LR, and Burnett AL. The epidemiology of sexual dysfunctions. J Sex Med 2008;5:289–300.


Introduction

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

Epidemiology can be defined as the population study of the occurrence of health and disease, with an ultimate goal of maintenance of the former and prevention of the latter. The oft-quoted statement of the World Health Organization [1] to the effect that “health is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity,” reminds us that defining health can sometimes be as demanding an enterprise as a delineating disease. Sexual health rests on being functional and unimpaired in the physical, psychologic, and relational aspects of sexual behavior, and conversely, it is almost certain that each of these facets of sexual behavior makes a tangible contribution to states in which sexual function goes awry.

There are numerous reasons why epidemiology is important to the science of sexual medicine. Epidemiology offers a powerful set of methods to potentially address questions about the nature, etiology, prognosis, and treatment of sexual disorders. In part, this is because cases of sexual dysfunction seen in the clinic represent only a minor fraction of the range of cases of sexual disorders present in the population. Also, because experimental manipulation of the major determinants of sexual dysfunctions is usually not feasible or possible, epidemiology contributes flexibility of design that enables the study of the impact of these factors via alternative methods.

The most fundamental study designs in epidemiology are referred to as observational studies, and within this category, a distinction is usually made between descriptive studies and analytic studies. Descriptive studies tend to be done when we know little about the nature, occurrence, or risk factors of the disorder. The principal goals of such studies are to establish reliable estimates of the frequency of the condition in the population under study, and perhaps generate useful hypotheses about the condition's etiology. In analytic studies typically, enough is already known about the disorder and its potential determinants to enable specific hypotheses to be tested. The identification of the risk factors of the condition and their causal association with the index disorder is the major focus of analytic studies.

A key aspect of analytic epidemiologic studies is establishing a relative index of association between the risk factors and the disorder under consideration, i.e., how convincing are the relationships between hypothetical risk factors A, B, and C, and the occurrence of the disorder. The relative weights of various risk factors are determined by measures of association which are themselves established by a number of factors: strength of association (in terms of exposure/nonexposure and presence of the condition), temporal relationships (risk factor antedates disorder), generalizability of the association (e.g., present in Asians, blacks, Caucasians), and specificity of the association (necessity/sufficiency of the risk factor of the disorder). However, estimating the relative importance of risk factors can become complicated when the condition under study is multifactorially determined, as are the sexual dysfunctions, with either alternative (A or B or C) or cumulative (A + B + C) patterns of causation.

Relationship Between Epidemiology, Nosology, and Standardized Methods

In the case of sexual dysfunctions, the large majority of our epidemiologic studies are observational–descriptive in nature, with the reporting of very few analytic trials. This is so in large measure because our nosology, or diagnostic system, is relatively imprecise and our methods are neither standardized nor very clearly articulated. Writing specifically in reference to psychiatric epidemiology, Allen and his colleagues stated, “The availability of a widely accepted and reliable diagnostic system is an essential prerequisite to . . . epidemiology.” Further, they made the point, “Epidemiologic research is impossible without clear and consistent methods of classifying and diagnosing . . . disorders”[2]. Imprecise diagnostic definitions result in imprecise estimates of occurrence rates, and very much impede meaningful attempts at evaluating risk factors. Inconsistent methods continually hamper the attempts of gaining the consensus estimates of the population rates of dysfunction. Dunn and her colleagues, referring to their 2002 review of 28 studies of female sexual dysfunction (FSD) [3], stated, “. . . the heterogeneity of studies ruled out the possibility of formally pooling the data. Furthermore, this variety of methodology, study design, and case definitions . . . meant that giving a reliable overall estimate of the different sexual problems was not possible” (p. 418). Similarly, Hayes and his associates recently concluded in their review of prevalence studies of FSD, “As measures of sexual dysfunction and time frames differ between studies, it is still not possible to determine reliable overall prevalence estimates of FSD” (p. 594) [4].

The large majority of epidemiologic investigations of sexual dysfunctions have involved estimates of the prevalence of various conditions. However, it is important to realize that the methods of data collection in these studies have been extremely variable, including mailed surveys, telephone interviews, rarely, scores on validated test instruments, and even more rarely, in-person interviews. In the current review, we will limit our evaluation to studies completed circa 1990 and thereafter. This is because prevalence data from earlier studies of sexual dysfunctions tended to use heterogeneous case definitions, in some cases focused on “symptoms,” in others on “problems,” and only rarely on formal “disorders.” The design methodology also varied enormously in these earlier trials as was pointed out in Spector and Carey's review of 47 earlier studies in 1990 [5]. An updated review by Simons and Carey in 2001 summarized the results of 52 FSD studies accomplished since the previous review [6]. They were able to develop a pooled current and 1-year prevalence estimate of 7–10% for orgasmic disorder; however, they concluded that in spite of some improvement in standardization, because of extreme heterogeneity, it remained difficult to pool results across studies. They stated, “. . . despite the increased attention in the past decade to the study of sexual dysfunctions there appears to have been relatively little methodological improvement overall” (p. 215).

These problems represent a fundamental limitation for contemporary research in sexual medicine, and while there are appeals to the field to effectively address these pervasive issues [7,8], our current epidemiologic research remains strongly encumbered by the absence of a more rigorous diagnostic system and the use of a standardized methodology.

Practical Matters and Current Standards

Additional factors also influence attempts to derive frequency statistics for sexual dysfunctions. Perhaps of greatest concern is the extent to which sexual disorders, that essentially require self-reporting, are perceived to be problematic for the affected individuals. Affected individuals with erectile dysfunction (ED), for instance, may not perceive the disorder to be a problem for them, either in terms of degree of distress or significance as a life-threatening condition. Also, for disorders associated with social stigmatism, which may be such for sexual disorders, the presence and extent of the problem, as reported, may significantly vary from their actual occurrences [9]. The influence of cultural, religious, and legal norms may impact the estimations of sexual problems within a community of interest. The availability of regular sex partners among surveyed individuals may also affect the assessments of sexual function. Finally, it is important to consider the time frame of the investigation. In the current era of effective oral medication to treat ED, following the advent of phosphodiesterase type 5 inhibitor therapy in 1998, there has been an increased public health awareness surrounding ED and its societal impact, possibly generating greater acknowledgment and acceptance of the widespread presence of sexual disorders.

Epidemiologic research of sexual dysfunctions has evolved formatively in the direction toward increasingly rigorous investigative methodology. Early reports in the literature commonly derived estimates based on persons having sexual disorders seen in a hospital, clinic, or doctor's office. For instance, patients evaluated in an endocrinology clinic for diabetes mellitus permitted an opportunity to ascertain the presence and frequency of an associated sexual disorder such as ED occurring among those with the primary disease state. Such studies afforded insight into the risk relationship between a particular sexual disorder and the primary disease state and further suggested pathophysiologic mechanisms accounting for the disorder. However, such studies reflect select populations, and thus, do not serve to describe the circumstances of the sexual problem as it affects the broad population. More recently, peer-reviewed scientific literature has emerged based on studies that apply contemporary probability-based sampling strategies, and thus, yield data that are representative of the population at large. These reports are believed to offer a refined understanding of the true population frequencies of sexual dysfunctions, appropriate for advancing meaningful global public health efforts to address them.

Based on recent consensus guidelines, contemporary standards of assessment for epidemiologic studies should apply external and internal validation [10]. External validity requires the definition of the source population, description of eligibility according to such features as age range and inclusion and exclusion criteria, confirmation of a response rate of at least 70% of the sample studied, specification of the study period, and adequate characterization of the study population (e.g., age, gender, presence of comorbidities, socioeconomic status). Internal validity requires prospective data collection, application of validated (and properly used) measurement instruments, and statement of the definition of the sexual disorder under study (see above).

Measures of the Frequency of Disorder

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

In order to do science in almost any area of discourse, methods must be developed to promote the quantification of outcomes; in the case of epidemiology, these measures are focused on the quantification of disorder occurrence. As raw counts of occurrence have little meaning, in and of themselves, more sophisticated indices have been developed to reflect factors like the reference population, those at risk, and the period over which observations were made. Although there are numerous indicators of the frequency with which disease occurs, the two fundamental indicators are the prevalence and incidence of the disorder.

Definition of Prevalence

Prevalence is defined simply as the proportion of existing cases in a population relative to the total population at risk at a particular point in time. It essentially communicates the probability that an individual in the population will have the disorder at a specific point in time. This form of prevalence is referred to as point prevalence, as the reference period is a specific point in time.

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A second important measure of prevalence is referred to as period prevalence. This measure of prevalence enumerates the number of cases of the condition occurring in the population under study during a specific period of time (e.g., 6 months, 12 months, lifetime). Period prevalence combines information on existing cases with occurrences of new cases of the disorder.

Definition of Incidence

Incidence is defined as the number of new cases of a particular disorder that develop during a specified time period. It essentially represents an estimate of the risk of developing the condition during the specified time window.

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Because incidence reflects the emergence of new cases, and thereby a change in health status during the measurement period, many epidemiologists feel that it represents a measure that is very well suited to study risk factors. Prevalence on the other hand, is a function of both prior incidence and duration of the index condition. If a condition has a brief duration, then prevalence tends to be low; however, if illness duration is chronic, even with a low incidence rate, cases will accumulate over time and prevalence will be high relative to incidence. Currently in sexual medicine, because of the gradual and uncertain onset of most sexual dysfunctions, the large majority of epidemiologic studies report occurrence in terms of prevalence data.

Male Sexual Dysfunctions

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

Prevalence of Male Sexual Dysfunctions

The Massachusetts Male Aging Study (MMAS) is perhaps recognized as the first population-based study offering a determination of the prevalence rate of ED [11]. This study, which comprised a sample of 1,800 men surveyed in a Boston, MA area from 1987–1989, reported a prevalence rate of 52% for any level of ED (including minimal, moderate, and complete presentations) and that of 35% for moderate or complete ED. The study also documented the relationship of age and ED, determining that the prevalence rates of complete ED (no ability to achieve an erection) increased from 5% to 15% for men between the ages of 40 and 70 years. The study comprised mainly of Caucasian men within this age range only, and thus, it is not useful to draw conclusions about national variations in race and ethnicity or the prevalence of ED in men over the age of 70 years.

The National Health and Social Life Survey, a cross-sectional interview survey conducted in 1992, which included 1,410 men aged 18–59 years throughout the United States, found that approximately 10% of the respondents had “trouble maintaining or achieving an erection,” and the prevalence of any form of sexual dysfunction in men was 31% [12]. The study also evaluated sexual dysfunctions other than ED including low desire (approximate overall rate of 15%), and inability to achieve orgasm (approximate overall rate of 8%). An age-associated decline in sexual problems was also confirmed. Compared to the referent group of men aged 18–29, the oldest cohort of men (ages 50–59 years) were more than 3.5 times as likely to experience ED (95% confidence interval [CI], 1.8–7.0), nearly three times as likely to experience low sexual desire (95% CI, 1.6–5.4), and two times as likely to experience inability to achieve orgasm (95% CI, 0.79–3.83). “Climaxing or ejaculating too rapidly” was the most commonly indicated sexual dysfunction in this study, affecting approximately 30% of respondents with similar rates across age groups.

The Health Professions Follow-up Study, which involved a sample of more than 31,000 men aged 53–90 years surveyed in 1992, found that ED based on the conservative criteria of poor to very poor function was 33%, ranging from about 25% among those younger than 59 years to 61% in individuals older than 70 years [13]. The study also demonstrated that many aspects of sexual function decreased sharply by decade after 50 years of age. For age groups 53–59 years, 60–69 years, 70–79 years, and older than 80 years, respectively, “very good” overall sexual function was 44%, 25%, 8%, and 2%; “very good” sexual desire was 34%, 24%, 12%, and 6%; and “very good” ability to reach orgasm was 51%, 33%, 13%, and 4%. The study also reported the extent to which sexual function is a “big” problem, with percentages for the respective age groups of 3%, 7%, 13%, and 19%.

A report based on the release of the 2001–2002 National Health and Nutrition Examination Survey (NHANES), a population-based survey comprising of 2,126 men from 20 to greater than 75 years of age representing broad racial and ethnic groups in the United States, established an 18.4% ED prevalence rate, based on self-reporting of being “sometimes able or never able to keep an erection adequate for sexual intercourse”[14]. An age relationship with ED was shown, with a prevalence of ED, as previously defined, found to increase steadily from 6.5% in men aged 20–39 years to 77.5% in those 75 years and older. The percentage of the participants with the most severe ED, measured by reporting being never able to maintain an erection, increased from 2% to 47% between the indicated age categories. Hispanic men reported ED at approximately twice the rate as Caucasians (12.5% vs. 4.9%), after controlling for other ED-related factors such as diabetes, obesity, and hypertension [14]. Modifiable risk factors independently associated with ED included diabetes mellitus (odds ratio [OR], 2.69), obesity (OR, 1.60), current smoking (OR, 1.74), and hypertension (OR, 1.56).

A separate analysis of the 2001–2002 NHANES database, corroborated the aforementioned analysis, also establishing 18.4% ED prevalence rate for the United States male population [15]. Further analysis of the cardiovascular risk factors established age-adjusted ED prevalence rates of 38.6% (95% CI, 28.7–49.5) among men with diabetes mellitus, 15.1% (95% CI, 10.6–20.9) and 27.7% (95% CI, 21.4–35.0) among men with treated and untreated hypertension, respectively, 24.7% (95% CI, 18.1–32.7) among men with a history of cardiovascular disease, 17.0% (95% CI, 14.3–20.1) among men with hypercholesterolemia, 19.6% (95% CI, 13.9–26.8) among men with history of benign prostate enlargement, and 23.3% (95% CI, 20.0–27.0) and 12.6% (95% CI, 9.8–16.2) among men performing no physical activity and vigorous physical activity, respectively.

Another nationally representative survey, the Male Attitudes Regarding Sexual Health Survey, conducted in 2001–2002, included men older than 40 years of age and oversampled minority individuals. In this study, the estimated prevalence of moderate or severe ED, defined as a response of “sometimes” or “never” to the question, “How would you describe your ability to get and keep an erection adequate for satisfactory intercourse?” was 22.0% (95% CI 19.4–24.6) overall [16]. ED prevalence rates were 21.9% (95% CI, 18.8–24.9) among 901 non-Hispanic white men, 24.4% (95% CI, 18.4–30.5) among 596 non-Hispanic black men, and 19.9% (95% CI, 13.9–25.9) among 676 Hispanic men. The study found that rates increased with age, diabetes, hypertension, and moderate or severe lower urinary tract symptoms.

Additional studies have recently been conducted affirming the global extent of male sexual disorders. The Global Survey of Sexual Attitudes and Behavior represented a collection of data of more than 27,000 men and women aged 40–80 years conducted between 2001 and 2002 in 29 countries [17]. “Early ejaculation” was the most commonly reported dysfunction in men occurring at a 14% (95% CI, 14–15) rate, having the greatest frequency in Asia, Central/South America, and non-European Western countries. “Erectile difficulties” were the second most frequent dysfunction in men, reported as an overall rate of 10% (95% CI, 9–10), with the greatest rates in Asian countries. An age-dependent decline in all male sexual functions including lack of sexual interest and inability to reach orgasm was confirmed in this study.

The Men's Attitudes to Life Events and Sexuality Study, a survey conducted in 2001 of more than 27,500 randomly recruited men aged 20–75 years in eight countries including the United States, the United Kingdom, Germany, France, Italy, Spain, Mexico, and Brazil, produced an overall ED prevalence rate of 16% [18]. Similar to prior discussed studies, the prevalence of ED increased with increasing age and the presence of comorbid conditions such as cardiovascular disease, hypertension, dyslipidemia, and depression.

Overall, notwithstanding variations in definitions, methodology and study populations, these reports substantiate the global presence and extent of sexual dysfunctions in men. ED has been the most thoroughly studied dysfunction, with an estimated overall prevalence rate that ranges between 10% and 20% worldwide. Racial/ethnic and geographic analyses affirm the significance that one in five men experience ED. However, other sexual dysfunctions are also common. The studies have also affirmed the correlates of age and comorbid health conditions with various sexual dysfunctions.

Incidence of Male Sexual Dysfunctions

Few epidemiologic studies exist which address the incidence of male sexual dysfunctions. Such studies are valuable to assess the risk and plan treatment and prevention strategies. Longitudinal results of the MMAS with follow-up through 1997 have offered population-based incidence data for ED [19]. The crude ED incidence rate was 25.9 cases/1,000 man-years (95% CI, 22.5–29.9) among men aged 40–69 years. The annual incidence rate increased with each decade of life: 12.4 cases/1,000 for men aged 40–49 years (95% CI, 9.0–16.9); 29.8 cases/1,000 for men aged 50–59 years (95% CI, 24.0–37.0); and 46.4 cases/1,000 for men aged 60–69 years (95% CI, 36.9–58.4). The age-adjusted risk was found to be higher for men with lower education, diabetes, heart disease, and hypertension.

The MMAS database was also used to examine coronary risk factors that may predict the development of ED in a “healthy” subsample of men free of ED or vascular disease at baseline [20]. Among several risk variables, cigarette smoking, cigar smoking, passive exposure to cigarette smoke, and overweight status were significant predictors of incident ED.

A side analysis of the recently conducted Prostate Cancer Prevention Trial has also produced incidence data for ED [21]. The trial, which began in 1994, consisting of more than 18,800 men aged 55 years or older, was designed to assess whether finasteride would reduce the prevalence of prostate cancer over a period of 7 years. Among 9,457 men randomized to the placebo group, 2,420 men (57%) of 4,247 men without ED at study entry reported incident ED after 5 years, and this rate increased to 65% at 7 years. Interestingly, the study showed that incident or prevalent ED generated a hazard ratio of 1.45 (95% CI, 1.25–1.69) for subsequent cardiovascular events, which is estimated to be in the range of risk associated with current smoking or a family history of myocardial infarction.

Female Sexual Dysfunction

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

Nosology of FSDs

Before reviewing the epidemiologic studies of FSD, it is relevant that we first briefly review the diagnostic system currently in use to classify these conditions. The nosology utilized in the FSDs has been based on a traditional four-phase model of the female sexual response cycle put forward by Masters and Johnson in 1970 [22]. Subsequently, Kaplan modified the paradigm slightly to focus on the three principal phases of desire, arousal and orgasm[23]. This model then formed the basis for the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, fourth version (DSM-IV) system [24]. In 1998, the system was further modified slightly as a result of the American Foundation of Urologic Disease (AFUD) international consensus conference on FSD [25]. Major diagnostic categories delineated at the AFUD conference were hypoactive sexual desire disorder (HSDD), female sexual arousal disorder, orgasmic disorder, and sexual pain disorders. This fourfold classification is essentially descriptive in nature, based entirely on clinical phenomenology, with no basis in pathophysiology or etiology. In addition, in the DSM-IV and AFUD systems, sexually related personal distress must be manifest before a diagnosis can be made. As the distress criterion was only adopted in recent years, the case definitions of earlier studies where, distress was not a diagnostic criterion, are not comparable to those of recent research. Also, judgments as to whether or not the condition has existed for the patient's lifetime or been acquired, and whether it is situational or generalized in nature are aspects of the contemporary nosology.

Beyond these considerations, there are a number of other influences that can have an impact on clinical judgment in an FSD condition, causing its precise nature to be unclear and obscuring the appropriate diagnosis. A brief inventory of these factors is listed below:

  • • 
    The symptoms from various categories are often comorbid.
  • • 
    Personal distress levels may be difficult to estimate.
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    Age is a differential factor in the prevalence of FSD.
  • • 
    Menopausal status must be factored into judgments.
  • • 
    The partner's sexual health and presence must be considered.
  • • 
    Depression and its treatment are frequent concomitants of FSD.
  • • 
    The duration and severity of the disorders are often highly variable.
  • • 
    Premorbid sexual functioning can be difficult to assess.

Prevalence of FSDs

Probably the most frequently quoted recent study addressing the occurrence of FSD is that of Lauman et al. (1999) [12] reporting on data from the National Health and Social Life Survey conducted in 1992. These investigators reported on the risk of experiencing sexual dysfunction based on a national probability sample of 1,749 women between the ages of 18 and 59, based on in-person surveys. They observed an overall endorsement rate for sexual problems among women at 43%; with approximately 32% indicating problems with a “lack of interest in sex.” A latent class analysis on the sample generated four principal categories of which “low sexual desire“ was one, with a prevalence rate of 22%. Arousal problems had a prevalence of 14%, with sexual pain disorders endorsed by 7% of the sample. It is important to note that these rates are based on a survey instrument and not on a clinical diagnosis, and while some data were generated concerning the anxiety that the respondents felt about their sexual problems, there was no measurement of sexually related personal distress.

Reporting on a sample of 703 Viennese women, using a questionnaire designed specifically for the study, Ponholzer and his colleagues observed somewhat similar results [26]. Approximately 22% of the sample indicated problems with low sexual desire; however, 35% of the women endorsed arousal problems, and 39% reported orgasmic difficulties. Sexual pain disorders were reported by 12.8% of the sample. Age proved to be a substantial risk factor for increased rates of FSD. Observing a similar rate, Addis and associates [27] found that “lack of sexual interest” was endorsed by 23.2% of a midlife random sample of Kaiser Permanente members, while 40% of a multiethnic sample who comprised the Study of Women's Health Across the Nation cohort endorsed low sexual desire in a questionnaire assessment [28]. Neither of these studies assessed distress associated with the desire problem. Paralleling these estimates, the Global Study of Sexual Attitudes and Behavior found rates of lack of interest ranging from 24% to 43% in different regions of the world [29]. However, Segraves and Woodard pointed out that as only approximately 50% of women who admit to having a sexual problem also report being distressed about it, rates of diagnosable sexual dysfunction, as defined by contemporary standards, will be considerably less than the observed 24–43% [30].

A number of recent reviews have been published on the epidemiology of FSD that have proved to be very informative. Dunn and her associates published a review in 2004 of 28 studies on selected categories of sexual dysfunction, and also addressed the persistent methodological problems associated with FSD research [3]. Unfortunately, of the major FSD diagnostic categories, only orgasmic and pain disorders were included in their report. Overall estimates suggested a rate of 25% for orgasmic disorder, and the 1-year prevalence of female sexual pain disorders had a prevalence of between 1% and 21%. The nature of the relationship between pain prevalence and age proved controversial, with some studies showing a direct relationship between age and pain prevalence, and others suggesting that the relationship is inverse.

Additional instructive reviews have also been published within the past several years. Lewis and his associates [31] accomplished a review which covered both male and female dysfunctions, as well as prominent risk factors. They concluded that estimates of the prevalence of low sexual interest among women in the studies they reviewed showed high variability, ranging from 17% to 55%. They appear to distinguish between low “interest” and low desire, which they characterize as having a prevalence of 10% in women up to 49 years of age, and then increasing to 22% among the 50- to 65-year-old group. Arousal/lubrication disorders were found to range between 8% and 28%. They found high variability in estimates of female orgasmic dysfunction with rates generally clustering around 25%, but reported two Nordic studies in which over 80% of women endorsed problems with orgasm to some degree. Pain disorders also proved highly variable with a low estimated prevalence of 2% in an elderly British population and some estimates as high as 18–20% in several British and Australian studies.

Hayes and his colleagues at the University of Melbourne in Australia published a thoughtful methodologic review on the epidemiology of female dysfunctions in 2006 [32]. Their report also considered the duration of the conditions in those studies that reported such data. The review found desire disorder to be the most prevalent FSD condition with a mean of 64% and a range of 16–75%. Desire problems were followed by orgasmic difficulties at 35%, range 16–48%, and arousal disorders at 31%, range 12–64%. On average, 26% of respondents reported pain disorders, with a range of from 7–58%. Of the studies they reviewed, only two (Fugl-Meyer and Fugl-Meyer [33] and Bancroft et al. [34]) investigated the presence of sexually related personal distress, which ranged from 21–67%.

An interesting trio of studies was published very recently (2006–2007) based on the Women's International Study of Health and Sexuality (WISHeS), which was conducted in 1999 and 2000 via mail survey and personal interview on a large cross-sectional market research database of 4,517 women aged 20–70 years. The participants included women from the United States, the United Kingdom, Germany, France, and Italy. These reports are somewhat unique because validated self-report questionnaires, the Profile of Female Sexual Functioning (PFSF) [35] and the Personal Distress Scale (PDS) [36], were utilized as the case-defining criteria. Dennerstein et al. [37] focused their report on the prevalence of HSDD in menopausal women from the four European countries. Score on the PFSF Desire scale were used to identify those individuals with low desire, while scores on the PDS determined women with high manifest distress. The sample was partitioned into premenopausal women, surgically menopausal women aged 20–49, surgically menopausal women aged 50–70, and naturally menopausal women. Rates of low sexual desire were 16%, 29%, 46%, and 42%, respectively. However, when distress levels were factored in to determining cases of HSDD, the rates became 7%, 16%, 12%, and 9%. These estimates were contrasted with those reported by Fugl-Meyer and Fugl-Meyer [33] based on a Swedish sample, one-third of whom indicated they suffered from low desire, but only 43% of whom were distressed by it. The estimate of HSDD in that sample was 14%.

Using the same database, Hayes and his associates [38] analyzed the data looking at the relationship between HSDD and aging. Partitioning the sample into European and American respondents, rates of low desire progressed from 11% among 20- to 29-year-olds to 53% among women in the 60–70 age group among Europeans and from 22% to 32% among comparable American samples. In both samples, there was a definite increase in rates of low sexual desire associated with age. Concomitantly, the nature of the relationship between age and distress was inverse, falling from 65% to 22% among Europeans, and 67% to 37% across the age range among American women. This disordinal relationship between low sexual desire and sexual distress resulted in a nonsignificant relationship between age and HSDD across the age range, with prevalence estimates ranging from 6% to 13% in Europe, and from 12% to 19% in the United States.

Also, using the WISHeS dataset, Graziottin [39] estimated the prevalence of desire, arousal and orgasmic disorders based upon PFSF and PDS case definition criteria. She observed a significant intercountry variation, with the highest rates of dysfunction in Germany and the United Kingdom, and the lowest rates in Italy and France. As an example, low desire was reported by 21% of French women and 28% of Italians, while rates were 36% and 34% in Germany and the United Kingdom. Data on arousal and orgasmic disorders were similar, demonstrating the potential for considerable intercultural variation. As was emphasized in the previous report, there was a strong relationship between prevalence and age across all dysfunctional categories. Graziottin subsequently went on to review the implications of these data for clinical assessment, and explored etiologic differentiation and prognostic implications.

Incidence of FSDs

Because of some of the complexities outlined above, there are only a few published incidence studies of FSDs. Kontula and Haavio-Mannila published the results of a 5-year incidence study in a Finnish population, 18–74 years old [40]. The investigation was focused on low sexual desire which was endorsed by 45% of the women. This rate was highly age dependent; however, as the rate among women less than 25 was approximately 20%, the incidence among women over 55 was 70–80%. A similar 40% incidence of low desire was reported by Fugl-Myer in a 5-year incidence study in a Swedish population. A more detailed evaluation revealed that 11% of the sample reported suffering from “severe” reduction of sexual desire [41].

Discussion

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

After decades of tentative data on rates of occurrence, rendered indistinct by imprecise diagnostic definitions and uncertain science, recent epidemiologic research has established some findings that appear consistent and reliable. For example, there is now little doubt that sexual dysfunctions, in both males and females, have a substantial prevalence in the United States and throughout the world, and that there is a relatively unambiguous relationship between frequency of dysfunction and age in both men and women.

Depending on age demarcation and severity of the condition under evaluation, rates of ED have been consistently observed to increase from approximately 2.5 to 4.0 times as age progresses from men in their 20s to men in their 70s. Overall rates of ED ranged from 10% to 20%, with the majority of studies reporting an overall rate closer to 20%. The findings suggest that rapid ejaculation (RE) is the most prevalent male dysfunction with rates of occurrence ranging from 14% to 30%; however, RE does not show a systematic relationship with age, and rates are relatively constant across the adult lifespan. A much less systematic review has been available for the other male sexual dysfunctions, such as low sexual desire and inhibited ejaculation, although there also appears to be a significant relationship between prevalence and age for these conditions as well.

Among studies of women, low sexual desire was the most prevalent of the dysfunctions, and this appears to be so across the age range, including both premenopausal and postmenopausal women. There are some data to suggest that surgically menopausal women may have a higher prevalence than naturally menopausal women, which may be related to lower levels of androgens in this group. Generally speaking, low sexual desire systematically increases with progressing age, with occurrence observed to be two to four times greater in oldest vs. youngest cohorts. The overall frequency of reported low sexual desire did vary considerably depending on the composition of the sample, with reported frequencies ranging from 10% to 64%. Several studies reported an overall prevalence of 22%, with other studies reporting very similar rates for one or more subgroups. Although conservative compared to some findings, there appears to be a consensus for a rate of 20–25% for low sexual desire.

A confounding issue involves the necessary presence of manifest personal distress in both the DSM-IV and AFUD systems required to make a formal sexual diagnosis, including one of HSDD. This nosologic innovation creates problems from an epidemiologic perspective, because although clinical manifestations of low desire have a direct linear relationship with age, personal distress shows a strong inverse relationship. The result of this disordinal interaction between low desire and personal distress across age is that most studies report rates of HSDD as constant throughout the age range even though problems with low desire clearly increase with age. Also, with the introduction of personal distress as an obligatory diagnostic criterion, there is now a major inconsistency between the case definitions used in current epidemiologic studies, and studies completed in earlier periods.

Another very uniform finding, in the case of males and females, is that certain medical and health conditions are reliably identified risk factors for sexual dysfunction. Specifically in the case of ED for men, diabetes, cardiovascular disorders, hypertension, dyslipidemia, obesity, smoking, and prostate disorders all show a positive relationship with the occurrence of ED. Among women, there are also substantive relationships between health factors and rates of sexual dysfunction. Chronic illnesses and poor general health status tend to be associated with higher occurrences of sexual dysfunction among women. In terms of specific conditions, diabetes, breast cancer, lower urinary tract problems, surgical removal of the ovaries, multiple sclerosis, and clinical depression have all been consistently found to show significant associations with FSD. Although prevalence estimates vary with gender, age, illness duration, illness severity, and case definition, there is a clear evidence for sexual liability associated with a number of highly prevalent medical conditions. It should be noted in addition, that many of these medical disorders have a strong independent association with age, which makes age an even more insidious risk factor for sexual dysfunction.

Beyond age and health status, there are a number of other risk factors for sexual dysfunction that have been explicitly identified in recent years. Although we will not systematically review the body of evidence here, there is a very clear confirmation that specific categories of prescribed medications have a high risk of dysfunction associated with them. In particular, psychiatric drugs such as antidepressants and antipsychotics have a clearly demonstrated liability for sexual problems, as do antihypertensives, some anticonvulsants, and H2-blockers. There is also an evidence that certain specific drugs (e.g., digoxin) foster sexual problems in some individuals [42]. We must conclude from these data that not only do certain medical conditions place an individual at increased risk for sexual problems, but that in certain instances, our choice of treatment can make an independent contribution to risk for sexual dysfunction as well.

It is impossible to contradict the fact that definite advances have been made in our knowledge of the population occurrence of sexual dysfunctions, almost exclusively in terms of the prevalence of these conditions. We must remain cognizant of the fact, however, that we still have much work ahead of us in establishing a rigorous epidemiology of sexual medicine. A very significant deficiency in the field concerns the paucity of studies of the incidence of sexual dysfunctions. This is because, in a large measure, of the fact that incidence estimates require longitudinal assessment across time, thereby involving expensive and time-consuming trials. We cannot do a reasonable job of estimating the risk and instituting sexual health prevention programs, however, unless we know when, where, and in whom new sexual liabilities emerge. This is probably a goal that can be tackled most expeditiously by federal agencies.

As has previously been stated, precise epidemiology is very much dependent on rigorous nosology or diagnostic nomenclature, which we currently do not have in place. Serious efforts must be made in the field to establish a uniform nosology, with consistent definitions of dysfunctions for both men and women. The new nomenclature should be free of any specific theoretical orientation, and be acceptable to a sizeable enough proportion of clinicians in sexual medicine to establish a meaningful diagnostic convention. Only when this is accomplished will we be able to do careful analytic epidemiology addressing specific risk factors and their degree of association with sexual dysfunctions. Until this step is taken, no matter how rigorous our clinical trial designs, we will remain in a “half a loaf” position because we will lack unified, meaningful definitions of the diagnostic entities we seek to evaluate.

Beyond what has already been said, we want to emphasize that we believe strongly that any new diagnostic system should include measurements of severity and duration of dysfunction if we are to optimize knowledge in the field. Such assessments do not have to be complex, with a simple ordinal Likert scale of “mild,”“moderate,”“severe” reflecting severity and duration recorded in months/years. These measurements would greatly increase the utility of current reports of “lifetime” vs. “acquired,” which provide the minimal information that duration was either “continuous” or “noncontinuous.” Severity assessments will also help establish whether the nature of the condition is more likely to be transitory and remitting, or enduring and profound, and will also help reduce variation in our estimates of occurrence by rendering trial samples more homogeneous.

Conclusion

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References

The current review of the epidemiology of sexual dysfunctions has documented specific clear results that have emerged consistently for both men and women. Within both genders, there is little doubt that sexual dysfunctions are highly prevalent in our society, and that the prevalence of sexual dysfunctions increases directly with age. There are also strong data to support the ancillary finding that while the frequency of dysfunctional symptoms increases with age, personal distress about those symptoms has an inverse relationship with maturation. Distress appears reduced as individuals become older. Another very reliable finding is that certain medical conditions and health behaviors represent major risk factors for sexual disorders, and that many of these health conditions also have a strong positive relationship with age. Therefore, we must conclude that age should be assigned dual impact as a risk factor, both directly through the maturation process, and indirectly through its relationship with specific medical conditions, strongly suspected to be etiologic agents for sexual disorders.

Although we have observed improvement in both the number and quality of epidemiologic prevalence studies in sexual medicine, there is a dearth of studies of the incidence of these conditions. These studies are important for the prevention and treatment planning regarding sexual disorders, and their development and execution should become a top priority for the field. We have also observed repeated calls for the development of a new systematic and integrated diagnostic system in sexual medicine, because the poor quality of our current nosology is viewed by many as the “rate-limiting step” for the epidemiology of the field. Analytic studies designed to rigorously evaluate the risk factors can only be accomplished if our case definitions are uniform and reliable, thereby enabling us to take the next important scientific steps. It appears reasonable to conclude from the current review that although much has been accomplished in the past two decades, a great deal remains to be done.

Conflict of Interest: None declared.

References

  1. Top of page
  2. ABSTRACT
  3. Introduction
  4. Measures of the Frequency of Disorder
  5. Male Sexual Dysfunctions
  6. Female Sexual Dysfunction
  7. Discussion
  8. Conclusion
  9. References
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