© 2009 THE AUTHORS 1698 JOURNAL COMPILATION © 2 0 0 9 B J U I N T E R N A T I O N A L | 1 0 5 , 1 6 9 8 – 1 7 0 4 | doi:10.1111/j.1464-410X.2009.09040.x 2009 THE AUTHORS. JOURNAL COMPILATION 2009 BJU INTERNATIONAL Sexual Medicine GENETIC AND ENVIRONMENTAL EFFECTS ON THE CONTINUITY OF EJACULATORY DYSFUNCTION JERN et al. Genetic and environmental effects on the continuity of ejaculatory dysfunction Patrick Jern, Pekka Santtila, Ada Johansson and N. Kenneth Sandnabba Center of Excellence in Behavior Genetics, Department of Psychology, Åbo Akademi University, Turku, Finland Accepted for publication 12 August 2009 first sexual intercourse and a concurrent self-report of the same at the time of data collection in a population-based sample of 2633 Finnish twins and their siblings aged 18–48 years (mean 26.63, SD 4.68). The continuity of ejaculatory function was assessed by correlation and multiple regression. Reasons for continuity were separated into genetic and environmental sources using twin-model fitting. RESULTS Ejaculatory function, particularly PE, was stable over time. Genetic effects accounted for ≈30% of the variance in PE both at first intercourse and when measured at data collection. Unshared environmental effects accounted for most of the variance (≈70%). Genetic effects were almost identical between the sample occasions, but there was a substantial discrepancy between unshared environmental effects affecting PE at first intercourse and unshared environmental effects affecting PE later in life. Age effects were generally negligible. Data were self- reported and retrospective, and thus vulnerable to response bias. CONCLUSIONS Ejaculatory dysfunction seems to be temporally stable both in the short and long term. Genes that contribute to the variance in PE at first intercourse are similar to those that contribute to the variance in PE later in life, whereas there are, in this regard, substantial differences in the unshared environmental factors that are a cause of PE. KEYWORDS ejaculatory dysfunction, premature ejaculation, continuity, twin study Study Type – Symptom prevalence (retrospective cohort) Level of Evidence 2b OBJECTIVES To investigate temporal continuity in ejaculatory dysfunction by comparing self-reported experiences of premature ejaculation (PE) at first intercourse with self- reported PE and delayed ejaculation at present, and to clarify whether and to what extent genetic or environmental factors affect continuity in ejaculatory dysfunction, as previous studies indicate moderate heritability for PE at first intercourse. SUBJECTS AND METHODS The study comprised retrospective self- reported data on ejaculatory performance at INTRODUCTION Although premature ejaculation (PE) is regarded as one of the most common sexual dysfunctions in men [1], little is known about its persistence over time. No long-term follow-up study has been conducted to investigate the temporal dimension of ejaculatory dysfunction (EjD). However, stability of ejaculatory problems is very much expected, and even taken for granted both in the academic and clinical setting. For example, the very definition of lifelong PE [2], as suggested and accepted by the International Society of Sexual Medicine, implies that the condition is stable and permanent. However, the definition itself only refers to the present: ‘Lifelong PE [. . .] is characterized by ejaculation that always or nearly always occurs [. . .] and inability to delay ejaculation on all or nearly all vaginal penetrations’ [3]. There is no suggested period for the duration of the condition. While several studies have indeed measured ejaculatory function over short periods (especially clinical drug-trial studies), relatively few have reported the test-retest reliability statistics for the measures. Symonds et al. [4] reported intraclass correlation coefficients of 0.73 for test-retest reliability on patient-reported outcomes during a 4-week study with data collected on three separate occasions during this time, while Patrick et al. [5] found intraclass correlations of 0.63–0.87 for intravaginal ejaculation latency time (IELT) and patient- reported outcomes in subjects with PE and their partners over a 2-week period. A Belgian study found high within-subject repeatability for ejaculation latency times with intraclass correlations of 0.88–0.93 [6]. Althof et al. [7] found test-retest reliability correlations of 0.70–0.90 for a questionnaire measuring sexual satisfaction, control and distress associated with PE for a period of 7–10 days. These findings indicate a substantial temporal continuity in EjD, at least over short periods. For longer periods there are no such statistics, but the stability of PE over longer periods is indirectly suggested by Pryor et al. [8], whose participants reported a mean duration of PE of ≈16 years in a clinical drug-trial study. The temporal stability of PE is also implied by Hawton et al. [9], who found that 75% of men who initially responded to behavioural therapy for PE showed no lasting improvement after 3 years of follow-up. It is generally agreed that PE is not explained by one cause [10]; affective and cognitive psychological experiences [11], genetics [12,13], neurobiology [14], physical BJUI BJU INTERNATIONAL