Lycopene intake and the risk of erectile dysfunction in US adults: The National Health and Nutrition Examination Survey 2001–2004

Abstract

To the Editor,

We recently read with great interest an article published in Andrology titled “Lycopene Intake and the Risk of Erectile Dysfunction in American Adults: The National Health and Nutrition Examination Survey 2001–2004.¹” The study analyzed data from the National Health and Nutrition Examination Survey (NHANES) collected between 2001 and 2004, involving 3265 male participants, 931 of whom had erectile dysfunction (ED). The potential relationship between dietary lycopene intake and the prevalence of ED in American adult males was examined using dose-response curve analysis, logistic regression models, and 1:1 propensity score matching. The findings indicated an inverse association between lycopene intake and ED, suggesting that increased lycopene consumption may reduce the likelihood of developing ED.

While we commend the authors for their valuable contribution, several concerns warrant clarification. Firstly, according to the NHANES analytical guidelines, researchers are advised to use survey weights in their analysis to ensure an accurate representation of the US population.² The complex, multi-stage probability sampling design employed by NHANES requires the use of appropriate survey weights to produce nationally representative estimates. This is essential, as unweighted data may lead to biases due to the oversampling of specific subgroups. However, the article does not specify whether a weighted analysis was performed or which survey weights were applied. Clarification on this point is requested, as the proper selection and application of survey weights are critical for the accuracy and validity of the study's findings.

Secondly, there appears to be a discrepancy between the description of the ED questionnaire in the article and the information provided by NHANES. In NHANES, ED is assessed with the question, “How would you describe your ability to get and keep an erection adequate for satisfactory intercourse?” with responses categorized as “Always or almost always able,” “Usually able,” “Sometimes able,” and “Never able.” However, the article states that ED diagnosis was based on responses to the question, “Have you ever had ED?” with a binary yes/no response. To the best of our knowledge, NHANES does not include this specific question. We suggest that the authors align the definition of study variables with the actual NHANES questionnaire content to avoid misleading readers. Furthermore, according to the European Association of Urology guidelines on sexual and reproductive health, ED is typically classified into primary organic ED and primary psychogenic ED.³ The use of a single question to diagnose ED in this study does not allow for differentiation between these categories. Considering the reported benefits of lycopene, such as its anti-inflammatory and antioxidant properties, as well as its positive effects on endothelial cells, these effects are likely more relevant to primary organic ED, particularly vascular-related ED. The impact of lycopene on primary psychogenic ED remains unclear.

Thirdly, we have methodological concerns regarding the study. The definition of depression in the study relies solely on a single question: “During the past 12 months, have you had a period of two weeks or longer when you felt sad, depressed, or empty?” However, the NHANES database provides data from the Patient Health Questionnaire-9 depression scale, which could offer a more comprehensive and validated assessment, considering that depression is a significant risk factor for ED. Additionally, lycopene intake was assessed using two days of dietary recall data, with the first-day data used if the second-day data were unavailable. We believe that relying on a single day's dietary recall may not accurately capture an individual's usual intake, and utilizing only the two-day recall data would likely yield more reliable results. Finally, ED patients may use Phosphodiesterase type 5 inhibitors to improve erectile function, which could influence their responses to the ED questionnaire. Since NHANES includes data on the use of these medications, conducting a sensitivity analysis to exclude such individuals could strengthen the robustness and validity of the study's findings.⁴

In conclusion, we highly appreciate the authors' remarkable contributions to the comprehension of the relationship between lycopene intake and ED. Their creative utilization of NHANES data, in conjunction with strict statistical methods, provides highly valuable insights into potential dietary approaches for managing ED. We are convinced that this study establishes a solid foundation for future research in this domain. Addressing the methodological points we put forward would further strengthen the reliability and influence of these findings, ultimately contributing to the progress of nutritional interventions for men's health.

All authors contributed equally to writing and finalizing this manuscript.

The authors declare no conflict of interest.