Erectile dysfunction: heritability and cognitive and physiological correlates of the subclinical vascular disorder
MetadataShow full item record
The broad goals of this dissertation were to explore possible causes of erectile dysfunction (ED), and examine outcomes associated with the condition. To address these objectives, data from the Vietnam Era Twin Study of Aging (VETSA), a longitudinal study of cognitive aging, were utilized. Previous research demonstrated moderate heritability of ED in middle-aged men, but questions remain about the replicability of these findings given that only one study exists on the topic and it utilized an unvalidated ED measure. Additionally, it is unknown to what extent genetic factors account for stability and change of ED symptomatology over time. In the first study, we conducted a longitudinal assessment of ED using the Sexual Health Inventory for Men (SHIM) administered to 668 male twins. Results revealed that the heritability (proportion of variance explained by genetic factors) of ED at both time points is moderate (0.3 –0.6). Over the past two decades ED has been recognized as primarily a disorder of vascular dysfunction. Inflammation is an important correlate of vascular dysfunction. Chapter 2 examined the association of ED with four inflammatory serum protein indices [albumin, globulin, albumin/globulin ratio (AGR), and the albumin*globulin interaction (AGI)] in 388 men free from cardiovascular disease (CVD). Results indicated that the AGR, albumin, and globulin protein levels are significantly associated with ED, even after accounting for other risk factors. Intriguingly, AGR and globulin levels were found to be more strongly associated with ED than conventional vascular risk factors, such as hypertension, high cholesterol, obesity, and smoking. As such, globulin and AGR may be useful biomarkers when diagnosing and managing ED. The simplicity and affordability of these assays make these markers particularly valuable. Given the negative impact that vascular disease has on cognition, Chapter 3 explored whether men with ED are at greater risk for experiencing cognitive decline compared to healthy peers. In total, 485 men free from CVD were administered cognitive tests across 13 domains. Tests were readministered 5 years later. Results revealed that men with ED were more likely to show significant decline on tasks of set-shifting, tool/mechanical knowledge, vocabulary, and verbal fluency.