Risk Factors of Sexual Dysfunction
Such a classification should be internationally accepted. One way of classification of severity of sexual desires has been the use of well validated indices, an example for men, the IIEF [3] and for women, the FSFI [4]. There have also been scales suggested which can be as simple as yes/no answers or four-graded and six-graded itemized scales. Useful trichotomized scales including no dysfunction (never), mild dysfunction (hardly ever, rather rarely) and manifest dysfunction (rather often, often, always/nearly always) have been suggested as a useful scale to classify severity.
Incidence
There is clearly a need for more longitudinal studies for all of the dysfunctions in order to obtain more accurate incidence data. Incidence rate for erectile dysfunction comes from three studies. Two, from the United States and Europe, suggest an incidence rate of 25–30 cases per thousand person years. The rate was higher in the third study from Brazil. In all of the studies, rates increase markedly with each decade of age [5,6,7].
Incidence of sexual dysfunction in women is supported even less by evidence-based literature.
Prevalence
Prevalence rates for sexual dysfunction are strongly supported by evidence-based reports. Literature supporting these prevalence rates was reviewed in WHO chapter [8]. Evidence-based literature for prevalence rates was graded using a modification of the system suggested by Prins and others in their 2002 article in the International Journal of Impotence Research [9]. A summary of this is provided in Table 1. There is a variance in the prevalence rates reported because of different age groups reported on, difference in definitions used to describe the dysfunctions, how the data were selected, how the data were collected, how long the dysfunction was present, and the degree of the dysfunction.
Table 1
Criteria for the methodological quality assessment of prevalence studies—one point for yes to lower case query
External validity
Source population
(a) Does the method to select and invite participants result in a study population that covers the complete population or a random sample?
Description of the eligibility criteria
(b) Is the age range specified?
(c) Are inclusion and exclusion criteria specified?
Participants and nonresponders
(d) Is the response rate >70%, or is the information on nonresponders sufficient to make inference on the representativeness of the study population?
Description of the study period
(e) Is the study period specified?
Description of the study population
(f) Are important population characteristicsa specified?
Internal validity
Data collection
(g) Are the data prospectively collected? Measurement instrument (questionnaire, interview, additional)
(h) Is the measurement instrument validated?
(I) Is the period covered by the measurement instrument specified?
Definition of diseases n
(j) Is a definition of the disease stated? Reported prevalences
(k) Are age-specific and gender-specific prevalences reported?
(l) Are possible correlates of diseaseb reported?
Informativity
(m) Is the method of data collection properly described (interview, questionnaire, additional measurement)?
(n) Are the questions and answer possibilities stated?
(o) Are the reported prevalence rates reproducible?
a Two or more of: (i) age distribution; (ii) relevant co-morbidity; (iii) lifestyle factors (e.g., smoking and alcohol consumption); and (iv) socio-economic data (e.g., income, education level, marital status).
b Disease equals erectile dysfunction in this interview.