Use of a confirmed mathematical method for back-analysis of IELT distributions: ejaculation time differences between two continents and between continents and men with lifelong premature ejaculation (Part 1)

The rs6296 polymorphism in the 5-HT1b receptor in Dutch men with lifelong premature ejaculation: a genetic case-control association study

BACKGROUND

Lifelong premature ejaculation (LPE) is a rare sexual condition believed to be caused by genetic neurobiological disorders.

AIM

In this study we sought to evaluate the genetic association between the rs6296 polymorphism of the 5-HT1b receptor and intravaginal ejaculation latency times (IELTs) in men with LPE compared with men in a control group.

METHODS

This study was a prospective observational genetic case-control association study. The LPE definition of the International Society for Sexual Medicine (ISSM) 2013 was used. Patients were recruited in 2005-2009 while attending the department of Neurosexology, HagaZiekenhuis, the Netherlands. We obtained IELTs with the stopwatch method. Polymerase chain reaction (PCR) was used for genotyping rs6296. A randomly selected group of European Caucasian men from the 1000GENOMES project was used as a control group.

OUTCOMES

Study outcomes included results of comparisons of analysis of variance (ANOVA) tests between genotypes and IELTs in study participants, genotypes of cases and controls determined with the chi-square test, and expressions of allelotype- and genotype-specific risks for LPE determined with odds ratios.

RESULTS

In total, 67 men with LPE were included in this study. The geometric mean (SD) IELT was 32.0 (27.4) seconds and was non-normally distributed. Genotype frequencies consisted of 29 (43.3%) GG, 31 (46.3%) GC, and 7(10.4%) CC individuals in the LPE group. Log-transformed IELTs were not statistically significant (per ANOVA tests) in men with GG, GC, or CC genotypes (P = .54). Genotype frequencies consisted of 16 (6.6%) GG; 93 (38.8%) GC, and 131 (54.6%) CC individuals in the control group (n = 240). Significant differences were found when comparing allele (P = 1.02e-17) and genotype (P = 3.22e-16) frequencies in cases and controls using a chi-square test. A statistically significant increased risk for LPE was found for carriers of the G allele (OR 5.62; 95% CI 4.13-9.42). Statistically significant risks were also found for the CG genotype (OR 6.24; 95% CI 2.63-14.77) and the GG genotype (OR 33.92; 95% CI 12.79-89.93).

CLINICAL IMPLICATIONS

By investigating polymorphisms in target genes the neuro-pathophysiology of LPE could be further elaborated, potentially leading to more effective treatment.

STRENGTHS AND LIMITATIONS

This is to our knowledge the first study investigating rs6296 with regard to LPE. By using a strict definition for LPE (ISSM 2013) and using the stopwatch method for measuring IELTs, bias in selection of true LPE patients will be relatively low. This study is limited by a relatively small study population and the lack of IELT data in the control group.

CONCLUSIONS

This study shows a genetic association in rs6296 in men with LPE compared with healthy controls. This result warrants attempted replication in future studies.

Current and emerging treatment options for premature ejaculation

Premature ejaculation (PE) is a prevalent male sexual dysfunction. Current standard treatment regimens include behavioural therapies, topical anaesthetics, dapoxetine and other selective serotonin reuptake inhibitors (SSRIs). Most of the pharmacotherapeutic options target neurotransmitters (such as serotonin and oxytocin) that have a role in the ejaculation mechanism. However, these treatments are mildly effective and only provide a temporary delay in the ejaculation latency time, and PE recurs when the treatment is stopped. Thus, a treatment for PE is urgently needed and research is ongoing to find the ideal PE therapy. The efficacy and safety of topical anaesthetics and SSRIs in delaying ejaculation have been confirmed in many well-designed controlled trials. Both preclinical and clinical studies on new-generation SSRIs are ongoing. Moreover, promising results came from clinical trials in which the efficacy of on-demand PE therapies targeting neurotransmitters other than serotonin, such as α1-adrenoceptor antagonists and oxytocin antagonists, was assessed. Surgical intervention and neuromodulation have been proposed as potential treatment options for PE; however, current PE guidelines do not recommend these treatments owing to safety concerns.