New research underscores the critical role of lipid profiles in men's health, revealing that higher atherogenic index levels may not only signal heart trouble but also significantly increase the risk of erectile dysfunction.
Study: Association between the atherogenic index of plasma and erectile dysfunction in US men: a population-based cross-sectional study. Image Credit: Rocos / Shutterstock
In a recent study published in the International Journal of Impotence Research, a group of researchers thoroughly examined the relationship between the atherogenic index of plasma (AIP) (the ratio of triglycerides to HDL cholesterol, a predictor for the severity of coronary artery disease) and erectile dysfunction (ED) (the inability to maintain an erection) using data from the National Health and Nutrition Examination Survey (NHANES).
Background
Erectile dysfunction (ED), which is the inability to achieve or maintain an erection for satisfactory intercourse, affects a significant proportion of men globally.
While not life-threatening, ED can significantly affect men's physical and mental health as well as relationships. It shares common risk factors with cardiovascular disease (CVD), such as atherosclerosis (artery narrowing due to plaque buildup), endothelial dysfunction (impaired function of blood vessel lining, affecting circulation), and inflammation, making ED a potential biomarker for CVD.
The AIP, a measure of cardiovascular risk based on lipid profiles, is gaining attention. However, the precise mechanisms linking AIP and ED require further exploration, particularly through large-scale and diverse population studies.
Understanding this relationship is clinically relevant as it could lead to better risk assessment and early intervention strategies for both ED and CVD.
About the study
The study population was drawn from the NHANES database, with all participants providing informed consent. NHANES uses complex sampling designs, interviews, laboratory tests, and physical exams to assess the health of the US population.
Data from two NHANES cycles (2001-2002 and 2003-2004) were selected for analysis, as these cycles included information on ED and the AIP. Exclusion criteria included participants over 70 years old (due to the higher prevalence of confounding health conditions), missing data on AIP or ED, participants over 70 years old, and those with incomplete information on relevant variables like poverty income ratio (PIR), body mass index (BMI), and hypertension.
Participants reported their ability to achieve and maintain an erection, with responses categorized as "never," "usually," "sometimes," or "almost always." Those who answered "sometimes" or "never" were classified as having ED. AIP was calculated as log10 (triglycerides (TG)/high-density lipoprotein cholesterol (HDL-C)). Covariates included age, BMI, blood glucose, PIR, ethnicity, cholesterol levels, marital status, diabetes, hypertension, education, CVD, alcohol intake, hyperlipidemia (High blood fat levels), and smoking status. These covariates were grouped into categories such as demographic factors, health conditions, and lifestyle factors for a more comprehensive analysis.
Statistical analysis was conducted using R software, applying sample weights to reflect NHANES' complex survey design. Linear regression was used for continuous variables, chi-square tests for categorical variables, and multivariate logistic regression to assess the relationship between AIP and ED.
A comprehensive set of sensitivity analyses was performed to confirm the robustness of the findings, particularly by applying a stricter definition of ED (patients who "never" achieved a satisfactory erection). This approach ensured that the observed relationships between AIP and ED were not due to methodological inconsistencies. Statistical significance was set at P < 0.05.
Study results
In the study, the AIP was significantly higher in participants with ED (0.21 ± 0.02) compared to those without ED (0.08 ± 0.01), showing a strong statistical difference (P < 0.0001). Additionally, individuals with ED tended to have higher levels of age, BMI, fasting blood glucose (FBG), TG, alcohol use, diabetes, CVD, smoking, and hypertension, while their levels of HDL-C, education, and PIR were lower. A higher proportion of ED patients were also married or living with a partner.
The study revealed a statistically significant higher AIP in participants with ED, indicating its potential as a biomarker for predicting ED risk. The association between AIP and ED was rigorously analyzed, with results indicating that AIP, treated as a continuous variable, was positively linked to ED.
This association remained statistically significant after adjusting for various factors like age, race, education, and marital status and after further adjustments for additional covariates. When AIP was divided into tertiles, a progressive increase in the odds of developing ED was observed across the tertile groups, further confirming the relationship between higher AIP levels and increased ED risk.
Sensitivity analyses further bolstered these findings, demonstrating that the association between AIP and ED was not only statistically significant but also consistent even when using stricter criteria for defining ED. A generalized additive model and smooth curve fitting further demonstrated a positive, linear relationship between AIP and ED.
Subgroup analyses revealed that the risk of ED was particularly pronounced among individuals over 50 years of age, non-Hispanic whites, those with cardiovascular disease, and individuals with lower or moderate BMI.
These findings underscore the importance of considering specific population characteristics when assessing the risk of ED associated with AIP. No significant interactions were detected across the analyzed subgroups.
In sensitivity analyses using a stricter definition of ED (patients who "never" achieved a satisfactory erection), the association between AIP and ED remained strong, confirming the robustness of the initial findings. The linear positive relationship between AIP and severe ED persisted in these analyses.
Sensitivity subgroup analysis also showed stronger associations in older individuals, those with moderate BMI, and patients with hypertension or diabetes, further emphasizing the link between AIP and ED, particularly in specific populations. When AIP was divided into tertiles, a progressive increase in the odds of developing ED was observed across the tertile groups, further confirming the relationship between higher AIP levels and increased ED risk.
Conclusions
To summarize, this study not only identified a significant association between higher AIP levels and an increased risk of ED among US men but also demonstrated the robustness of these findings through rigorous sensitivity analyses and detailed subgroup evaluations. Even after adjusting for potential confounders, the link between elevated AIP and ED remained strong.
These findings align with a similar study conducted simultaneously, further supporting the reproducibility of the results. Sensitivity analyses reinforced the relationship, and the study also found a higher prevalence of CVD among ED patients. This suggests that atherogenic dyslipidemia, indicated by elevated AIP, may play a role in the development of ED.
The implications for clinical practice are significant. Early assessment of AIP could be crucial for identifying individuals at heightened risk for ED, particularly in specific subpopulations such as those with CVD or metabolic disorders.
Future research should focus on elucidating the causal mechanisms underlying this relationship and on exploring the potential for targeted interventions to mitigate ED risk in high-AIP individuals.
Journal reference:
- Liu, G., Zhang, Y., Wu, X. et al. Association between the atherogenic index of plasma and erectile dysfunction in US men: a population-based cross-sectional study. Int J Impot Res (2024), DOI: https://doi.org/10.1038/s41443-024-00972-w, https://www.nature.com/articles/s41443-024-00972-w