Association of Erectile Dysfunction With Cardiovascular Risk Factors and Increasing Existing Vascular Disease in Male Chinese Type 2 Diabetic Patients

Patients were diagnosed as having type 2 diabetes using World Health Organization criteria (9) and underwent structured assessments using the EuroDiab Protocol (10). They were seen in a teaching hospital and tertiary referral center, but the government-funded health care system is such that many patients use the facility as their only source of subsidised medical care. Therefore, the study represents patients of low- and middle-income socioeconomic status.

All patients gave written, informed consent. Assessments for micro- and macrovascular disease, including retinopathy, peripheral vascular disease, and middle cerebral artery (MCA) stenosis using transcranial doppler, blood pressure, and fasting biochemical parameters, were performed as described previously (11,12). Using the 1993 National Institutes of Health Consensus Conference guidelines, ED was defined as the inability to achieve or maintain an erection sufficient for satisfactory sexual activity in the previous year. Difficulty in developing or maintaining a penile erection sufficient for sexual performance was reported during a physician-conducted diabetes complication screening.

Differences in parameters between those with and without ED were examined using the t test and χ² test. Backwards logistic regression analysis was used to determine independent predictors of ED. The following variables were incorporated into the model in three stages: first, age, age at onset of diabetes, and duration of diabetes; second, BMI, waist circumference, HbA_1c (A1C), triglycerides, HDL cholesterol levels, urinary albumin-creatinine ratio, and treatments for and histories of hypertension and diabetes, alcohol consumption, and smoking; and third, neuropathy, MCA stenosis, peripheral vascular disease, and retinopathy.

From the 1,078 recruited patients aged >30 years, 24.5% reported having ED. Patients reporting ED were generally older, and the prevalence rose significantly with age, increasing from 6.8 in those aged 30–39 to 35.8% in those >70 years. ED patients had worse glycemic control even though more ED patients underwent glucose-lowering treatment (P < 0.05, Table 1). Systolic blood pressure was higher in the ED patients, although 1.7 times more ED patients were receiving blood pressure–lowering pharmacotherapy (P < 0.001). In univariate analysis, raising glycemia and hypertension increased the risk for having ED with odds ratios (ORs) (95% CI) of 2.8 (1.2–6.8) and 1.8 (1.3–2.4), respectively, but not after adjustment for age and diabetic duration. ED patients had worse renal function and increased levels of micro- and most macrovascular complications (Table 1, P < 0.05)

Independent predictors of ED were determined in three stages. Age (aged 40–49, 50–59, 60–69, and ≥70 years having ORs [95%CI] of 2.5 [1.2–5.0], 5.9 [3.0–11.5], 5.3 [2.7–10.4], and 6.8 [3.3–14.1] compared with those aged 30–39 years, respectively) and duration of diabetes (1.1 [1.02–1.3]) were found to be independent predictors (χ² = 72.3, R² = 0.10, all P < 0.001). When anthropometric and biochemical parameters were incorporated into the regression analyses, age remained an independent predictor of ED, and albumin-creatinine ratio (1.3 [1.04–5.6]) and treatment for diabetes (4.6 [2.1–10.3]) were also included (χ² = 84.2, R² = 0.16, all P < 0.001). Inclusion of concomitant vascular disorders resulted in age, diabetic treatment (3.2 [1.3–7.8]), and neuropathy (2.9 [1.7–4.8]) being predictors of ED (χ² = 49.9, R² = 0.16, all P < 0.001).

Increasing age was closely related to ED, which is similar to observations in other populations (2,13–16). In Caucasians, risk increased 3.6 times in men aged 50–59 compared with those aged 18–29 years (2). The age-related risk in these diabetic patients was even greater at OR 5.6 (2.5–12.4) comparing the 50–59 year age-group with those aged 30–39 years, suggesting diabetes may accentuate the effects of aging on ED. Similarly, diabetes duration, a function of age, was also an independent predictor of ED and probably reflects the cumulative contribution of risk factors to the development of ED.

Higher glycemia increased the risk of ED. Even moderately high glucose levels affect the vasculature (17) and result in the accumulation of advanced glycation end products (18), which promote vascular disease and neuropathy and thus contribute to ED (18). Penile erection relies on neural stimulation of the penile vasculature endothelium and corpus cavernosum lacunae to trigger lacunae and smooth muscle relaxation and vasodilatation, which spurs filling and erection (19). Risk factors cause vascular damage, diminishing the response at a number of stages and promoting ED (17). Indeed, the albumin-creatinine ratio, a marker of renal function and vascular disease, was an independent predictor of ED, and existing vascular disorders increased with ED. Asymptomatic MCA stenosis was commonly identified (∼20%) but was not associated with ED, suggesting the pathogenesis of this condition may involve a different pattern of risk factors and may contribute to the high prevalence of stroke in Chinese populations (11,12).

The observed prevalence of ED of 24.5% is lower than the 63.6% from a smaller Hong Kong study (14), but it is comparable to a Singaporean study that reported 23.2% had mild ED (13). The disparity is probably due to methodological differences in diagnostic criteria, population selection, and recruitment timing, meaning direct comparisons of studies must be interpreted with caution but do give an estimate of the disease magnitude among the populations. ED patients often do not spontaneously seek help for their condition (6). Therefore, opportunistic screening for ED during visits to healthcare workers could help initiate early interventions to treat the ED and concomitant vascular risk factors to limit the progression of the associated diabetes complications.

In conclusion, Chinese diabetic patients with ED have higher levels of modifiable risk factors associated with vascular disease. Early recognition of ED and risk factor modification should reduce vascular disease.

This work was supported by the Hong Kong Research Grants Council Grants CUHK 4095/00M and 2041044.