Mismatch of partners in premature ejaculation (PE) regarding intra-vaginal ejaculation latency time (IELT) is usually neglected. Here we proposed the concept and evaluated the use of index of IELT (IIELT) as an objective diagnostic tool for PE. Data from 103 self-reporting PE patients and 59 normal controls were collected. The expected IELTs of both the male and female partners were provided by each participating couple in two questionnaires. IIELT=stopwatch IELT/(1/2 the male’s expected IELT+1/2 the female’s expected IELT). The stopwatch IELTs were 1.74±1.4 min (PE group) and 14.45±11.0 min (control group), P<0.05. The expected IELTs were 15.65±8.7 min (men) and 14.16±6.9 min (women) in the PE group, and 21.3±16.1 min (men) and 20.04±13.47 min (women) in the control group, P<0.05. The calculated IIELTs were 0.14±0.12 (PE group) and 0.83±0.60 (control group), P<0.05. The best cut-off point was 0.658, the Youden index was 0.652, sensitivity was 0.991, specificity was 0.661, positive predictive probability was 83.46% and negative predictive probability was 97.6%. We concluded that IIELT was an integrated measurement of the couples’ sexual equilibrium and demonstrated that it provided a simple and objective screening indicator for diagnosing self-reported PE.
Premature ejaculation (PE) is the most frequent male sexual dysfunction, even though the reported incidence rates vary significantly among reports using different diagnostic criteria.1, 2, 3, 4, 5, 6 Conventional algorithms on ejaculatory disorders are based on an organic or psychogenic dichotomy and now researchers realized the impact of PE on the couple as a whole, and intra-vaginal ejaculation latency time (IELT) is still one of the most important criteria for evidence-based definition of PE.7, 8 It is also frequently used for PE diagnosis based on patients’ sexual history and complaints.9, 10, 11 The International Society for Sexual Medicine guidelines recommend that patients who seek treatment for this complaint should be evaluated thoroughly and the treatment should be recommended based on the subtype (that is, lifelong, acquired, variable and subjective) they fall into.9 Based on this recommendation, many evaluation tools have been developed to characterize and/or determine the treatment efficacy of PE. These include PE diagnostic tool,12, 13 Arabic index of PE,14 PE profile,15 index of PE,16 and Chinese Index of PE.11 Although most of these diagnostic tools use IELT as a major measurement, a major drawback of them is that none takes into consideration both the difference between the expected and the actual IELTs, and the mismatch of the couple’s expected IELTs.
These factors are important to be considered in diagnosing and treating PE, which is a partner-oriented male sexual dysfunction.17 In large part, however, PE can be considered to result from the aforementioned mismatch between the male partner’s actual IELTs and the expected IELTs of his own or that of his partner’s. For example, if a couple can both reach orgasm within 1 min, they would not be bothered by the short IELT of 1 min. However, if a man ejaculates at 15 min and his partner needs 10 more min to reach orgasm or to feel satisfied, they will seek help because of the ‘short IELT.’ Although mismatch is a significant contributor to diagnosis and treatment-seeking behavior of PE patients, there is limited information in this neglected area in sexual medicine. Here we proposed a diagnostic tool, index of IELT (IIELT), to take these mismatches into consideration and to serve as an objective primary screening indicator for self-reporting PE. To our knowledge, this is the first study to specifically investigate this ‘sexual mismatch.’
Subjects and methods
From April 2013 to September 2013, male patients visiting Department of Infertility and Sexual Medicine, The Third Affiliated Hospital, Sun Yat-sen University, with main complaints of PE for at least 6 months, were recruited as participants in the PE group. The control group consisted of healthy volunteers who self-reported no PE. We posted recruitment advertisements with detailed study protocol in our website (www.xy778.com), in two nearby universities, in a community health education classroom and in our hospital. The basic requirement for the control group was that the couples should be healthy, without PE or erectile dysfunction for males. The male participants and their female partners were asked to participate in the study at the same time. Before study enrollment, all participants were informed about this survey and signed an informed consent form. The study was conducted in accordance with the Declaration of Helsinki and was approved by the Reproductive Ethics Committee of the Third Affiliated Hospital of Sun Yat-sen University.
Sample size decision
According to our pretest, we assumed the overall mean difference of IELT of normal men and PE men to be 10, a=0.05, β=0.10, s.d. of IELT=10 and the ratio of 1:4 for PE and normal group; the minimum sample size should be:
Self-reporting PE for at least 6 months were diagnosed.
All subjects were 20–45 years old, sexually active (having sexual intercourse once a week or more often), heterosexual and engaging in vaginal intercourse, and males without erectile dysfunction.
Male patients suffering from erectile dysfunction (diagnosed according to the International Index of Erectile Function-5 (<21 scores) were excluded. Both males and females suffering from genital diseases (such as deformity or infection), other systemic diseases (such as diabetes and cardiovascular disease) and psychiatric disorders (such as depression, obsessive compulsive disorder, anxiety, schizophrenia, insomnia and so on) requiring therapy were also excluded. Newlyweds or couples living in separate places were excluded.
At the first visit, male participants and their female partners were interviewed individually. A detailed medical and sexual history was recorded by experienced clinicians. All of the participants were required to fill the questionnaires, designed specifically for this study, independently. International Index of Erectile Function-5 was for males only, whereas Female Sexual Function Index was for females only.
IELT was assessed by stopwatch over a 1-month period. IELT was defined as the time period between the insertion of the penis and ejaculation occurrence. IELT had occurred before penis’ penetration into the vagina was recorded as 0 min. Females were provided with a stopwatch and instructions on how to record the IELT. The couples were required to experience a minimum of four coital attempts, with intervals of 3–7 days, and to calculate a mean IELT. They were instructed that if coitus took place more than once in a single session, only the first one would be recorded.
Calculation of IIELT
The IIELT is defined based on the actual IELTs and the expected IELTs from both partners. It is calculated using the following formula: IIELT=stopwatch IELT/(1/2 the male’s expected IELT+1/2 the female’s expected IELT).
Statistical analysis was performed using the computer statistical package SPSS/10.0 (Chicago, IL, USA). A P-value <0.05 was considered statistically significant. Continuous variables were expressed as x̄±s; for normally distributed variables, t-test was used. As the IELT usually followed a skewed distribution, we used the Wilcoxon’s rank test to calculate geometric mean IELTs instead of mean IELTs. The χ2-test or Fisher’s exact comparison was used for classification variables.
In this study, 111 couples in the PE group were surveyed, from which 8 couples were later excluded from the study because of incomplete information of the questionnaires. Sixty-one couples in the control group agreed to participate in the investigation; however, two couples were excluded due to the incomplete data.
In the PE group, male patients were 29.3±4.9 years old and female partners were 27.1±4.9 years old; in the control group, male patients were 31.0±5.8 years old and female partners were 28.5±4.9 years old. No significant difference was found for the age between the males of the two groups (P=0.876).
Female Sexual Function Index scores and characteristic of sexual intercourses
The PE group (44.2% (91/206)) and the control group (4.2% (5/118)) reported no or mild sexual intercourse satisfaction (see Table 1). The PE group (23.8% (49/206)) and the control group (1.7% (2/118)) reported no or mild sexual orgasm (P<0.01). Significant differences were found between the two groups regarding total Female Sexual Function Index scores and domain scores.
Intra-vaginal ejaculation latency time
For the PE group it was 1.7±1.4 min and it was 14.5±11.0 min for the control group (P=0.0023).
Estimated IELTs were 1.76±1.14 min (men) and 1.78±1.08 min (women) in the PE group, and 14.71±10.93 min (men) and 12.39±10.58 min (women) in the control group. No significant differences were found between estimated IELT and stopwatch IELT (PE group: for men P=0.532 and for women P=0.266; control group: for men P=0.885 and for women P=0.229) (Figure 1).
In the PE group, men’s expected IELT was 15.65±8.7 min and it was 14.16±6.9 min for women (P=0.24). In the control group, men’s expected IELT was 21.3±16.1 min and it was 20.04±13.47 min for women (P=0.91). However, between the two groups, the expected IELT was statistically significant (for men vs men, P=0.045; for women vs women, P=0.012; Figure 2).
Index of IELT
The calculated IIELTs were 0.14±0.12 for the PE group and 0.83±0.60 for the control group (P<0.01). IIELT is skewed. The percentile calculation of the 95% medical reference value range is 0.669–0.993. Area under the receiver operating characteristic curve was 0.907. According to Youden index: J=maximum (se+sp−1), to determine the group se and sp corresponding experimental values of the optimal cutoff point. For SPSS calculations based on optimal cut point of 0.658, a sensitivity of 0.991 and specificity of 0.661, Youden index was 0.652; for the optimal cutoff point we find a positive predictive value of 83.46% and a negative predictive value of 97.6% (Figure 3).
It is important that physicians regard PE as the couple’s problem18 and we included this in a single index, which could be useful in clinical practice.
IELT is an important indicator for PE diagnosis. It has been well accepted that short IELT, reduced or absent ejaculatory control and the presence of negative personal consequences should be considered when diagnosing PE.9, 10, 11, 19
Although IELT is an important measure for assessing treatment response, defining PE solely based on IELT does not accurately characterize PE.20 As we know, IELT distribution is positively skewed, and the median is the best for IELT description.6 The results of this study showed that in the PE group, only 1/3 patients complained <1 min of IELT (31/109) and there was no self-reporting IELT <1 min in the control group. There are four subtypes in the definition of PE, in which both variable PE and subjective PE are not defined with strict IELT time cutoff as lifelong PE and acquired PE.9 The common characteristics of the four subtypes are the inability to control IELT and the subsequent suffer and distress by the patients and/or their partners, which are the main reasons why patients present for treatment. Here we aim to investigate the effect of IELT on sexual satisfaction of both partners and we aim to investigate such effect in all subtypes of PE patients; therefore, we did not exclude the patients with a stopwatch IELT >2–3 min from the PE group.
IELT had no direct effect on satisfaction with sexual intercourse,20 but the mismatch of the time to achieve orgasm. Sexual orgasm and sexual satisfaction were not synchronized. Sexual satisfaction is a very complicated issue referring to mental or subjective feeling and involves more than IELT or partners coital orgasmic capacity alone. Orgasm is the extreme manifestation of sexual excitement, companying with obvious physiological responses and spiritual feelings. Reduced ejaculatory control and negative impact on sexual satisfaction were considered the central themes of PE.21 In general, male’s sexual satisfaction was accompanied with orgasm, not vice versa, that is, orgasm is not always accompanied with satisfaction. As for PE patients, although they routinely achieve ejaculation, they often feel frustrated and have low sexual satisfaction due to the short IELTs. If the IELT was much shorter than the female partners required for achieving sexual orgasm, then ‘sexual mismatch’ occured and became the main complaint that prompted them to seek medical treatment. This is why study showed female sexual function in the PE group was different from that in the control group. Our study showed that mean total Female Sexual Function Index score of the PE group female was significantly lower than that of the control; in addition, we found significant difference regarding the domain scores.
Mismatch between expected and actual IELTs was common in both the PE group and control group. Study showed that Ghanaian men desired IELT being from 10 to 25 min,which was much higher than the truth.22We also found in our study that both groups pursuitted longer IELT, with significant difference between the stopwatch and the expected IELTs. This result showed the unrealistic expectations for IELT were common for every man and woman, and that the key point was the gap between the expected IELT and the actual IELT. This result also suggested an adaptation to the sexual dysfunction of the partner or the expected IELT in partners of the PE group and an unrealistic expectation might lead to female sexual dysfunction. It was much easier for a couple to accept a minor gap and stay calm.
It is important to consider males and females as a whole when diagnosing PE. Neither self-estimated nor stopwatch IELT alone was optimal for assigning PE status.23 Many researchers realized females’ role in diagnosing and treatment of PE, and tried to carry out diagnostic tools for female roles related to partners’ PE.24 The pursuit of formulating an accurate definition of PE has been hampered by the fact that its causal mechanisms are poorly understood, leading to lack of a universally agreed-on definition and valid screening tools that capture diagnostically relevant features.25
IIELT is an important link to include males and females as a whole. Here we propose an intuitive and simple formula to calculate the mismatch between actual and expected IELTs, allowing doctors to quickly understand the situation of the patient and his partner, the reason we developed such an equation due to the fact that both male and female should benefit equally from sexual life. Our study suggested 0.658 as a cutoff value for IIELT. The most ideal condition should be IIELT=1. However, even for the control group, IIELT was <1, showing people’ unrealistic expectation for IELT. Although control couples also desire longer IELTs, a fact indicated by their IILET index numbers below the ideal IIELT=1, they are generally satisfied and would not seek medical treatment when IIELT >0.658.
IIELT could be used as a valuable screening indicator for self-reporting PE. Formula of calculating IIELT integrated both males and females, showing the important roles of both partners in diagnosing a male’s disease. IIELT reflects the diagnosis of PE for men and women in an overall concept, enriching the diagnosis criteria for PE. Our study, similar to other studies, also demonstrated that self-reporting and stop-watch measures of IELT were highly correlated and interchangeable.12 Thus, patients could also carry out in-home assessments of their ‘sexual mismatch’ without extra medical expense or equipment. IIELT could also help to improve the sexual harmony. For those with undesired IIELTs, couples should try to increase or decrease their expected IELT to reach sexual match.
The major limitation of this study was that we only considered IELT for the formula to calculate the sexual mismatch. Second, this study used self-report to measure time and it was possible that there might be a bias regarding the length of intercourse. Further research is needed to confirm and extend IIELT.
Our study showed that IIELT can be used as an integrated measurement of the partners’ sexual mismatch about IELT, and that it was a simple and objective screening indicator for diagnosing self-reporting PE.
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This research work was funded by the National Natural Science Foundation of China under grant number 81170533.
The authors declare no conflict of interest.
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Cai, L., Wen, Y., Jiang, M. et al. Premature ejaculation results from partners’ mismatch: development and validation of index of intra-vaginal ejaculation latency time. Int J Impot Res 28, 101–105 (2016). https://doi.org/10.1038/ijir.2016.7
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