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Letter to the Editor Penile Morphometrics and Erectile Function in Healthy Portuguese Men

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Letter to Editor

A recent study by Pereira examining penile morphometrics and erectile function in 1,416 healthy Portuguese men [1] provides novel data, but also flaws in statistical analysis, study design, data interpretation, and citation of previous findings. The main concern is Pereira’s claim that there was a statistically significant tendency for circumcised males to experience Erectile Dysfunction (ED). His Table 4 [1] compared Portuguese International Index of Erectile Function-5 (IIEF-5) scores for circumcised versus uncircumcised men, finding a marginal difference for IIEF-2 (p=0.048) and IIEFtotal (p=0.049), but no significant difference for IIEF-1, IIEF-3, IIEF-4 and IIEF-5. After Bonferroni correction, we found that significance disappeared (p=0.29 for each).

Survey-based cross-sectional studies run the risk of selection bias. In this regard, the sample was comprised of 81.8% uncircumcised men and 18.2% circumcised men, prevalence greatly exceeding a previous estimate of 0.61% for Portugal [2]. The high prevalence Pereira found is consistent with selective sampling leading to the overrepresentation of circumcised men in the study. In this regard, Pereira points out that “in Portugal the overwhelming majority of men are not circumcised, being only those who have some kind of clinical situation, such as phimosis and those who are referred for circumcision.” We suggest that men with a higher focus on their penis, for personal or medical reasons, are more likely to be ones who have a history of sexual function difficulties, of either pathophysiological or psychopathological origin, as was reported by Mao et al. for men circumcised for medical reasons [3]. Such men may be more likely to volunteer for inclusion in a study such as Pereira’s. It would be of interest to know the wording of the online recruitment advertisement he used to attract volunteers, but this was not stated. We, therefore, suspect selection bias.

Pereira cites three studies that he claims reported an association of ED with circumcision. However, the first of these (his reference 35) found the opposite, with that article stating: “In particular, the likelihood of having difficulty achieving or maintaining an erection is significantly lower for circumcised men.” His references 36 and 37 were small studies of men circumcised for medical problems, so raising the potential for confounding. The men’s ED may be a legacy of the problem for which they were circumcised, as reported by Mao et al., above [3]. Pereira’s reference 36 included men with diabetes, a known cause of ED, as well as phimosis, which was the reason for their circumcision.

In contrast, Pereira fails to cite high-quality cohort and randomized controlled trial data, as well as meta-analyses, comparing healthy circumcised and uncircumcised men, e.g. [4,5]. These studies have found no adverse effect of circumcision on any sexual function, including erectile function. The most recent meta-analysis identified four studies in which erectile function improved after circumcision [5].

Pereira speculated that the supposed circumcision-related ED he found was caused by “decreased sensitivity” of the penis in circumcised men. This is, however, contradicted by high-quality evidence detailed in large systematic reviews, e.g. [4].

Lastly, as for his finding that large penises were associated with lower erectile function, Pereira’s suggestion that aging was responsible should have been tested by comparing relevant data for older men with data for younger men.

In conclusion, we find that, when interpreted correctly, Pereira’s data confirms that circumcision does not cause ED. Pereira did find that circumcised men were satisfied with the appearance of their penis, and that penis size was unaffected by circumcision. When taken together with the finding that erectile function is unaffected, Pereira’s findings should reassure men requiring a circumcision that they have nothing to fear regarding these issues.

References

1. Pereira H. Penile morphometrics and erectile function in healthy Portuguese men. Andrology. 2020;9:204.
2. Morris BJ, Wamai RG, Henebeng EB, Tobian AAR, Klausner JD, Banerjee J, et al. Estimation of the country-specific and global prevalence of male circumcision. Popul Health Metr. 2016;14:4.
3. Mao LM, Templeton DJ, Crawford J, Imrie J, Prestage GP, Grulich AE, et al. Does circumcision make a difference to the sexual experience of gay men? Findings from the Health in Men (HIM) Cohort. J Sex Med. 2008;5:2557-2561.
4. Morris BJ, Krieger JN. Does male circumcision affect sexual function, sensitivity, or satisfaction?--A systematic review. J Sex Med. 2013;10:2644-2657.
5. Yang Y, Wang X, Bai Y, Han P. Circumcision does not have effect on premature ejaculation: A systematic review and meta-analysis. Andrologia. 2018;50:e12851.