Study of Association of Erectile Dysfunction with Metabolic Syndrome and Its Correlation with Endothelial Dysfunction in an Indian Population

INTRODUCTION

Erectile dysfunction (ED) is defined as the inability to obtain a penile erection sufficient for a satisfactory sexual performance. It is a prevalent disorder affecting >15% of men across the globe. ¹ The etiology of ED is multifactorial, and it is more common with increasing age. ^{2 , 3} The importance of ED is not only that it has a negative impact on the quality of life in men, ^{4 , 5} but epidemiological studies indicate that the occurrence of ED might increase the risk for coronary heart disease and suggests that a diagnosis of ED is a sentinel event that should prompt evaluation of coronary heart disease in the male population. ^{6 , 7} The main mechanism underlying the pathophysiology of both ED and cardiovascular disease (CVD) seems to be related to atherosclerosis and endothelial dysfunction. ^{8 , 9}

Metabolic syndrome (MS) is a cluster of metabolic abnormalities that starts with insulin resistance and continues with the addition of abdominal obesity, glucose intolerance or diabetes mellitus (DM), dyslipidemia, hypertension, and coronary artery disease. It has been shown to be associated with CVD by directly influencing vascular function. Therefore, it can be hypothesized that patients suffering from MS might have compromised sexual function. There is some literature available to suggest that patients with MS have more propensity for ED. ^{10 - 12} There is not much literature available in our population.

Early diagnosis of ED might provide an opportunity to unravel the risk of CVD. Therefore, the aim of our study was to determine the association of ED with MS and assess its correlation with endothelial dysfunction.

MATERIALS AND METHODS

This study was conducted in the Departments of Medicine, Surgery, and Radiodiagnosis, Era’s Lucknow Medical College and Hospital, Era University, Lucknow, Uttar Pradesh, India, which is a medical college hospital, between January 2017 and December 2018.

In this hospital-based cross-sectional study, 120 patients with MS [as per International Diabetes Federation (IDF) criteria] and 120 males as age-matched controls were included after ascertaining compliance with inclusion and exclusion criteria. Following enrolment, demographic information (age, place of residence, occupation, and socioeconomic status) was obtained from all the patients. Among cases, chief complaints and duration since the detection of MS were noted. A past history of medical illnesses was noted in all the cases and control, and they were inquired about their dietary habits and family history of systemic/chronic illness.

RESULTS

This was a hospital-based case–control study in which 120 male patients with MS and 120 age-matched controls were enroled. Demographic profiles, anthropometry, past illnesses, and patients’ medical history were obtained. Subsequently, with the help of the flow-mediated dilation method, endothelial dysfunction was estimated using ultrasound. All the cases and controls were assessed for ED using the IIEF score.

In the present study, the age of MS patients ranged from 20 to 59 years. The mean age of patients was 40.91 ± 11.41 years ( Table 1 ). The majority of patients were in the age-group 40–59 years (57.5%). The mean age of controls was 40.31 ± 11.33 years. There was no statistically significant difference in the age of cases and controls. The majority of cases and controls were from urban areas (64.2 vs 61.2%). The majority of cases (57.5%) had <6 months of history of MS.

Family history of systemic/chronic illnesses was reported in 19.2% of cases compared to 10% of controls, thus showing a significant difference between the two groups. The mean BMI, waist-to-hip ratio and hip and WC of the cases were significantly higher than those of the controls.

Prevalence of hypertension, glucose intolerance, central obesity, and dyslipidemia (low HDL and raised triglyceride levels) was significantly higher in cases compared to that in controls. Mean FMD values were significantly lower in cases (6.8 + 1.7%) compared to those in controls (12.8 ± 2.8%). With an increasing number of MS factors, a significant decrease in mean FMD values was observed. Prevalence of ED was 31.7% in cases compared to 5% in controls, thus showing a significant difference between the two groups. Mean IIEF scores were significantly lower in cases (18.82 + 5.59) compared to those in controls (23.00 + 2.57).

On univariate analysis, all five components of MS (hypertension, diabetes, central obesity, low HDL, and raised triglyceride levels were found to be significantly associated with ED. Mean BMI, WC, fasting blood sugar, systolic blood pressure, and diastolic blood pressure levels were significantly higher among those with ED compared to those not having ED, whereas mean HDL levels were significantly lower among those having ED compared to those not having ED as shown in Table 2 . With an increasing number of MS components, there was a significant increase in the prevalence of ED ( Table 3 ). Those with ED had significantly lower mean FMD values, as shown in Figure 1 (5.1 ± 1.1%) compared to those not having ED (10.9 ± 3.3%)

Fig. 1:

On multivariate analysis ( Table 4 ) evaluating the association of ED with hypertension, diabetes, central obesity, low HDL, high TG, FMD, and MS, only lower FMD levels were significantly associated with ED. A significant positive correlation was demonstrated between FMD and IIEF-5 scores ( r = 0.651; p = 0.001) as shown in Figure 2 .

Fig. 2:

DISCUSSION

Erectile dysfunction (ED) is a relatively common health problem but is considerably neglected. As lifestyle diseases such as DM, hypertension, and obesity are increasing, ED has also increased exponentially. In the present study, the prevalence of ED in patients with MS and its correlation with endothelial dysfunction was evaluated.

Erectile dysfunction (ED) is a major health concern in the aging male population across the globe. The prevalence of ED is 10–20% in the overall male population and reaches 50–60% at the age of 70 years. ^{16 , 17} The association of ED with CVD can be largely explained by common risk factors such as aging, diabetes, hypertension, obesity, dyslipidemia, and smoking, but ED is an independent predictor of CVD as well. ¹⁸

As widely known, MS represents a cluster of metabolic disturbances such as central obesity, hypertension, impaired glucose tolerance, and dyslipidemia, which are mainly derived from the accumulation of visceral adipose tissue and insulin resistance. MS and ED share a common pathophysiological mechanism; therefore, it is expected that the presence of MS may pose an increased risk of ED. Many previous studies have confirmed this. ^{19 - 22}

In the present study, the prevalence of ED among MS patients was 31.7% compared to only 5% in controls. Arrabal-Polo et al., in a case–control study, reported the prevalence of ED to be 64.9 and 9.5%, respectively, among cases and controls. ²³

A large population based on Suarez Arbelaez et al., including 36,911,824 subjects, concluded that MS and its individual components were significant risk factors for various urological disorders. ²⁴

Heidler et al. in a study of >2,000 men, observed that MS and central obesity are independently associated with an ED. ²⁰

Costa et al. conducted a study on 179 patients of ED and reported that lower total testosterone circulating levels were correlated with an increasing number of MS components, and the contribution of hypertriglyceridemia and WC was found to be strong. ²⁵

In the present study, we postulated that endothelial dysfunction could be an underlying reason for ED, and on evaluating and comparing the same between cases and controls, we found that flow-mediated dilation was significantly lower in cases of MS compared to controls.

Metabolic syndrome (MS) is known to affect endothelial function, and the findings of the present study also confirm this. The findings also showed that with an increasing number of components of MS, there was a decreasing trend of FMD values. Mazo et al. ²² in their study found endothelial function to be an important causative factor in the pathogenesis of ED among MS patients. As far as an association of MS components with ED was concerned, Lee et al. ²⁶ highlighted fasting blood glucose levels as the most significant independent factor associated with ED, while Amidu et al. ²⁷ found central obesity and raised blood pressure as the significant MS components associated with ED. In the present study, it was noted that an increase in the number of components of MS in cases was found to be associated with increased prevalence of ED and severity of ED, as suggested by a low IIEF-5 score. Similar results were reported by Lee et al., ²⁶ who found that with an increased number of MS components, there was a significant decrease in the IIPF-5 score.

It is possible that endothelial dysfunction might be an early marker followed by the development of atherosclerotic disease and arterial occlusion at a later stage. A link between endothelial dysfunction and ED among MS and future cardiovascular events was shown by various researchers. ^{11 , 28 - 31} In the present study, mean IIEF scores were found to be significantly lower in MS patients, and FMD values showed a significant positive correlation with IIEF values, as reported by Coban et al. ³²

In India, a landmark study conducted by Sood et al. in 357 patients with ED found that ED severity was significantly correlated with the presence of MS. ED was correlated with central obesity, serum TG, and fasting blood sugar. ³³

Another study from India, including 113 subjects of MS, reported that the presence of the various components of MS was associated with increased prevalence and severity of ED. ³⁴

The findings of the present study showed that there is a significantly increased prevalence of ED in patients with MS, which increases with a number of components of MS. It was noted that endothelial dysfunction was higher in MS patients, and it had a significant correlation with the ED. Hence, it is recommended that among MS patients, endothelial dysfunction should be assessed from time to time, especially among those male patients who complain of sexual problems.

There are only a few studies available in India addressing this issue. This is the only study that has found a correlation between ED and low-flow-mediated dilation in our population. However, the present study has a few limitations, as it is a hospital-based study with a small sample size. Being cross-sectional and observational in design, we could not follow these patients to determine the causal relationship between ED/endothelial dysfunction and CVD. We suggest further research addressing this arena with a large number of patients to validate our data.

CONCLUSION

The findings of the present study showed that there is a significant association between ED and MS. We observed that an increase in components of MS increased the prevalence of ED in MS. Endothelial dysfunction measured by FMD was correlated with ED.