Figure 36-1.
The five-step “allow” algorithm for managing sexual dysfunction.
This first step is crucial as it highlights the multifactorial nature of sexual dysfunction and provides the physician with the required information to make an informed decision about the next step in patient management. Once the provider has determined that further investigation is required, the committee recommends that the patient be educated properly on their diagnosis, with a focus on partnering with the patient to share in the decision-making process regarding the treatment. In the recommendation for therapeutic intervention, lifestyle modification is the first category emphasized, followed by psychological intervention, medical treatment, and surgery if appropriate. Finally, step five encourages the physician to continue to follow up with the patient to monitor progress in both symptom relief as well as overall sexual well-being [8]. The five-step approach reflects a trend toward a more holistic view of sexual dysfunction, encouraging the physician to create a more individualized treatment plan for their patient.
Screening checklists and questionnaires have also become a major component in sexual dysfunction diagnostics, and there are both pros and cons to this development. Screening checklists allow for an efficient and simple way to identify potential sexual dysfunction in a patient population. This is especially important as many patients may not come in with a sexual problem as their primary complaint and because patients often may not be completely honest about their problem [8]. Furthermore, screening checklists can be easily integrated into patient check-in and help prime physicians on where the dysfunction may lie. Similar to screening checklists, questionnaires are currently the primary format in which sexual dysfunction is evaluated. While similarly convenient, questionnaires are innately limited due to their brevity and generality and thus should not be used as a substitute for a detailed sexual history performed by the physician. Furthermore, due to their general nature, they may not address specific situational concerns encountered by the patient. This becomes especially true in the context of nonheterosexual patient population , as most questionnaires have been developed to address primarily heterosexual problems. It also presents issues when administering questionnaires in the context of a multicultural patient population, where cultural and linguistic barriers may interfere with proper comprehension and completion of the questionnaire [8]. Thus the future of sexual dysfunction assessment must work toward increased inclusivity as well as a continued integration between screening tools and physician-administered sexual histories.
Technological Advances
Imaging (Local and Brain)
Biomarkers
An association between biomarkers such as endothelial nitric oxide synthase (eNOS) polymorphisms and increased risk of erectile dysfunction has been established [11]. More research needs to be performed in correlating biomarker to drug response, as well as discovering new ones for other sexual dysfunctions.
Physiological Studies
EEG has provided emerging evidence in the study of human sexual response and understanding dysfunction [12]. More studies need to be performed to provide evidence for specific links between identifiable patterns and specific sexual dysfunctions. Quantitative sensory testing (QST) is a neurophysiological assessment method for small and large nerve fiber function. Its application to assess genital sensation could add valuable objective information about the assessment of sexual dysfunction in men [13] and women [14]. The roles of plethysmography and thermography in the assessment of sexual dysfunction in both women and men cannot be understated.
Future Directions in Sexual Dysfunction Treatments
Regenerative Medicine and Stem Cells
The goal of stem cell therapy is to regenerate damaged or dysfunctional penile tissue in order to restore functionality [15, 16]. Several forms of stem cell therapy exist, derived from different forms of progenitor cells including adipose, muscle, and bone marrow tissue-derived stem cells [17].
Stem cell therapy is starting to show beneficial effects in the treatment of erectile dysfunction, especially in the context of diabetes, aging, and hyperlipidemia [18]. More clinical trials are now actively enrolling patients. Growth factor therapy and gene therapy are also acquiring more research presence.
Somatic cells could be induced to pluripotent cells then to mesoderm, endoderm, or ectoderm (Figure 36-2). Adipose tissue-derived stem cells (ADSCs) have been investigated for their potential ability to repair damaged nerve tissue, specifically cavernosal nerve injury-related ED. Chen et al. found that the use of ADSCs was able to repair both the nerve and the penile fibrosis, restoring erectile function in rats [19]. Liu et al. went one step further by modifying ADSCs with hepatocyte growth factor, finding an enhanced curative effect on erectile function in diabetic rats [20].
Figure 36-2.
Somatic cells induction to pluripotent cells then to mesoderm, endoderm, or ectoderm [Reprinted from https://commons.wikimedia.org/wiki/File:Overview_of_iPS_cells.png. With permission from the Creative Commons].
Additionally exciting is the potential of ADSCs to repair structural abnormalities, such as those found in Peyronie’s disease. Gokce et al. experimented with local injections of ADSC into damaged tissue and found attenuation of structural changes associated with Peyronie’s disease, resulting in enhanced erectile function in rats [21].
Human umbilical cord blood stem cells (HUCB-MSCs) have also been studied for their therapeutic efficacy. In one of the first human studies exploring the efficacy of stem cell treatment of ED, two patients that were completely unresponsive to oral therapy were able to successfully sustain an erection independently, with a third patient achieving the same results after 3 months [22]. Bone marrow-derived stem cells have also been used, primarily in patients with post-radical prostatectomy ED, with very promising results and minimal side effects [23].
Pharmacological Interventions
The future pharmacological interventions and future uses are summarized in Figure 36-3 and detailed in the following sections.
Figure 36-3.
Future pharmacological interventions and future uses.
Male Pharmacological Targets
Future pharmacological interventions for men are highlighted in Figure 36-4.
Figure 36-4.
Male pharmacological targets.
D4 agonists are currently being looked at as one of the most potent centrally acting treatments for erectile dysfunction [24]. While similar in function to apomorphine, these specific receptor agonists lack the emetic properties that made apomorphine so problematic [25]. However, currently D4 agonists require intravenous administration, which may lessen their favorability. Dopamine agonists may also play an important role in the treatment of hypoactive sexual desire disorder (HSDD) , as pathways in the brain related to arousal are affected by dopamine [24].
PT-141 is an alpha-MSH analogue that can function to stimulate MC receptors and increase penile erection in men [26]. MC3 and MC4 receptors have become important targets in pharmaceutical research regarding the treatment of erectile dysfunction and will be an important aspect of future treatment [24].
The stimulation of 5-HT2 serotonin receptors has the ability to delay ejaculation [24]. Thus, SSRIs are currently being studied for their possible therapeutic effect on premature ejaculation). However, due to the fact that prolonged use of SSRIs can reduce sexual activity and lead to HSDD, prophylactic treatment with short half-life SSRIs before intercourse are now being suggested. Clinical trials for this pharmacological treatment are currently underway, but with mixed results [27, 28]. One approach to treatment of PE is a daily administration of an SSRI, with paroxetine showing the strongest ejaculation delay [29]. Adverse effects of this treatment may include mild nausea, fatigue, loose stools or perspiration, and symptoms usually disappear within 2–3 weeks of treatment onset [29]. A second approach to treatment is on-demand use of SSRIs which seems to be well tolerated by slightly less efficacious than daily administration [29].
Dapoxetine , an ejaculo-selective serotonin transport inhibitor, is the first pharmaceutical specifically developed for PE treatment [29]. A potent SSRI, dapoxetine, works by binding and inhibiting 5-HT, dopamine, and norepinephrine reuptake transporters [30]. It has been investigated as a strong candidate for an on-demand treatment of PE based on its pharmacokinetic profile [29]. Thus far, dapoxetine has successfully undergone two phase II trials and two phase III trials. Double-blind, placebo-controlled phase III multicenter trials were conducted to assess the efficacy of an on-demand use of dapoxetine, 1–3 h prior to sexual intercourse [29]. Results showed significant increases in intravaginal ejaculatory latency time (IELT) with dapoxetine compared with placebo in both phase III trials [29]. IELT increased from 0.91 min at baseline to 2.78 and 3.32 min for 30 and 60 mg dapoxetine, respectively [29]. Side effects of this treatment included headache, nausea, dizziness, and diarrhea [29].
Both ATP and adenosine are being explored for their potential positive effects on penile erection. ATP has been found to both initiate and maintain penile erections, modulating erectile function rather than acting as a direct neurotransmitter [31, 32]. It has also been found to relax the smooth muscle of the corpus callosum independently of nitric oxide [33]. Adenosine, which is a metabolic product of ATP breakdown, has the ability to act as an effective vasodilator with a very short half-life [34]. Several animal and human studies have revealed the increased penile tumescence with the administration of intracavernous adenosine injections [35, 36]. However, not all forms of erectile dysfunction are due to a problem with adenosine function, and thus treatment efficacy is limited [37].
The role of nitric oxide in vasodilation of smooth muscle of the corpus callosum has been well established. It has been recently discovered that NO stimulation and the corresponding increase in cGMP activate two separate protein kinases within the cell: PKG1a and PKG1b [38]. Diminished functionality of these two kinases has been found in erectile tissue of diabetic rats [38]. However, gene transfer of PKG1a into these diabetic rats resulted in restored erectile function [38]. Researchers are now targeting PKG1a gene transfer as a future treatment for diabetic patients with ED resistant to oral pharmacotherapy [24].
Heme oxygenase/carbon monoxide (HO/CO) is another pro-erectile gas currently being investigated, working similarly to NO in its ability to relax penile smooth muscle via cGMP pathways [24]. While studies thus far have not yet been tried on aging animals, preliminary findings suggest increased male sexual function including erectile function [39]. Further studies are needed to deduce the exact role that HO/CO plays in ED pathophysiology [24].
Female Pharmacological Targets
Due to the difficulty in clearly defining female sexual dysfunction (FSD) as well as objectively measuring sexual dysfunction in the laboratory, pharmacological treatment for females has been more difficult. There is an interplay of several various factors that contribute to FSD, thus selecting one specific target is often insufficient. It has also been suggested that the pathologic process of FSD follows a more circular model rather than a linear one, complicating matters further [40]. In terms of standard laboratory measures of sexual dysfunction, there seems to be a crucial dissociation between physiological measurements of sexual functionality and a woman’s subjective experience and satisfaction [41]. Finally, due to the fact that placebo has been determined as most effective treatment of FSD creates difficulty in truly understanding the efficacy of pharmacologic treatment [42, 43]. Nevertheless, there are several pharmacological targets currently being studied for their possible therapeutic effect on FSD as depicted in Figure 36-5.
Figure 36-5.
Female pharmacological targets.
Flibanserin is a 5-HT 1A agonist, 2A antagonist, initially created as an antidepressant that failed to prove general effectiveness during stage 2 trials. However, researchers found a trend in which almost all of their subjects were free of symptoms of sexual dysfunction [44]. Testing began on flibanserin for its possible efficacy in treating HSDD in females, yet its overall efficacy has proven tenuous. Initial phase III trials using e-Diary to measure daily sexual desire did not show significance over placebo [44]. However, flibanserin did show increases in satisfying sexual events (SSE) as well as an increase in Female Sexual Function Index (FSFI) and a decrease in Female Sexual Distress Scale (FSDS-R) [44]. Yet, despite these positive results, the FDA refused approval of flibanserin in 2009 due to its inability to show statistical significance regarding e-Diary scores as well as its side effect profile [44]. Side effects of flibanserin were found to include vomiting, drowsiness, and vertigo, which were dose dependent [44]. Furthermore, drug-drug interactions with fluconazole as well as its ability to suppress CYP3A4 lead to symptoms of hypotension and syncope [44]. These effects were further increased by an interaction with ethanol [44].
Due its high side effect profile, FDA rejected flibanserin’s NDA resubmission in 2013. Another notable concern presented by the FDA regarding flibanserin lies in the diagnostic criteria of HSDD and the drug’s potential off-label use. Due to the generalized and often subjective criteria for diagnosing HSDD, it is likely that flibanserin might be prescribed to patients who do not necessarily fit the HSDD label [44]. This may lead to a safety hazard, due to Flibanserin’s high side effect profile. However, it is important to note that several groups have come out in support of flibanserin, most notably even the score, which argued that disapproval of the drug by the FDA was a matter of gender inequality [44]. Despite these concerns, in 2015, the FDA finally approved flibanserin, under the condition that risk management tools would be enforced [44].
A selective dopamine (DRD3) agonist is currently under investigation by Pfizer for the treatment of FSD [45]. Dopamine agonists work by stimulating dopamine receptors in several dopaminergic pathways in the brain. The stimulation of these receptors can enhance approach behavior, possibly leading to pro-sexual behavior [46–48]. In humans, pro-sexual behavior due to dopamine agonists was first witnessed in patients with Parkinson’s disease who showed “hypersexual behavior” in response to treatment with pramipexole, a DA agonist [49, 50].
Apomorphine (APO) is also being studied as a primer for increased sexual function in women. Apomorphine was found to increase subjective arousal, self-reported lubrication, and peak clitoral blood flow velocity in premenopausal women with anorgasmia during vibratory stimulation [51]. APO was administered 40 min prior to vibrational stimulation, thus acting as a primer for sexual function [51]. A second study with APO revealed increased sexual enjoyment as well as an improved orgasm in female participants, without an increase in frequency of sexual encounters [52]. While therapeutic efficacy of APO looks to be promising, there is concern due to reported incidence of nausea, vomiting, and diarrhea, possibly limiting its effectiveness [52].
Bupropion is an atypical antidepressant given to individuals looking to avoid the negative sexual side effects of SSRIs. Currently, bupropion is being investigated for its potential benefit in nondepressed females with anorgasmia and sexual arousal disorder [53, 54]. Furthermore, PDE-5 inhibitors could act as an adjuvant treatment, enhancing the effects of buproprion peripherally without increasing central activity [55]. Currently, there are no human studies confirming the synergistic effect of PDE-5 inhibitors on buproprion, but animal work is promising.
Bremelanotide , created by Palatin Technologies, is an alpha-MSH analogue that preferentially binds to MC4 receptors. Bremelanotide has been found to have efficacy in the treatment of FSD [56]. Alpha-MSH works by targeting the paraventricular nucleus of the hypothalamus, which is thought to play a role in sexual desire [57]. An increase in the frequency of sexual satisfaction, arousal, and sexual desire has been reported in healthy premenopausal women undergoing phase II trials of bremelanotide [58–60]. However, increased blood pressure has been reported as a side effect of drug therapy [61]. Phase III trials will be complete in 2016, and an improved drug with less blood pressure effects will also be created [61].
The hormone oxytocin , released by the posterior pituitary gland, is also being explored as a treatment for FSD. Due to its ability to increase pair bonding as well as to decrease anxiety, it may work to alleviate psychological barrier inhibiting proper sexual function [62]. Several animal studies have been conducted on oxytocin, with findings revealing positive psychosocial effects, specifically female mate approach behavior [63]. Currently, two pharmaceutical compounds are being investigated—an OT receptor agonist and an enzyme inhibitor that slows down OT degradation [64]. However, the unpredictability of OT absorption through the blood-brain barrier limits its efficacy [64]. Future investigation of OT compounds will focus on its ability to reverse vaginal atrophy in female patients with genito-pelvic pain [65].
With regard to sex steroid hormone therapy , efficacy has been quite mixed. Androsorb, a testosterone cream created by Novavax, has shown increased libido in postmenopausal women and is currently in early clinical trials [66]. Tefina, is an intranasal testosterone gel which is currently being tested for its efficacy on females with orgasmic disorder [67]. Research subjects have reported feelings of intense arousal, with increased genital response relative to placebo [67]. LibiGel is transdermal testosterone gel specifically aimed at treating HSDD. It is currently being developed by BioSante Pharmaceuticals and has undergone two phase III trials known as BLOOM. However, phase III trials revealed that LibiGel was no more effective than placebo in increasing sexual desire. Currently, BioSante is conducting a phase III trial investigating LibiGel’s long-term safety. While testosterone supplementation for FSD looks to be promising, more investigation is necessary before a product is brought to market.
Alprostadil, initially established for male erectile dysfunction, is currently being investigated for its efficacious treatment of FSD. As a prostaglandin vasodilator, alprostadil has the ability to increase blood flow to the female reproductive tract as well as increase afferent nerve sensation [68]. Femprox is an alprostadil cream developed by Apricus Biosciences developed primarily for female sexual arousal disorder (FSAD) [68]. Thus far, it has been shown to increase primary arousal in nine clinical studies [68].
While supplemental DHEA is often used by postmenopausal women , findings indicate that systemic DHEA does not significantly benefit women with FSD. However, there have been positive results with the use of prasterone, an intravaginal DHEA, with reports of increased sexual function and sexual desire [69, 70].
Supplemental l-arginine has also been a topic of discussion regarding OTC therapy for FSD, as it has shown promise in its treatment of mild-moderate FSD [71]. Female subjects responded positively to treatment with l-arginine, showing increased sexual satisfaction, clitoral sensitivity, and frequency of intercourse compared with control subjects, in a 4-week placebo-controlled study [72]. Future positive results with l-arginine may result in a wide variety of OTC supplements.
Surgical Interventions
Surgical interventions (Figure 36-6), especially minimally invasive procedures, are gaining more traction for both men and women.
Figure 36-6.
Surgical interventions.
Penile revascularization is a type of surgery performed on the penile arteries in patients with erectile dysfunction. Typically these surgeries are performed on younger patients who have undergone major pelvic trauma, often resulting in a blockage of the internal pudendal arteries [73]. However, this type of surgery is not performed often, due to a high rate of long-term revascularization failure caused by slow runoff into the corpora when the penis is flaccid [74].
Venous ligation is another form of surgical treatment for erectile dysfunction. It has been well established that penile veins play an important role in maintaining erections [75]. These veins maintain erection by providing veno-occlusion, preventing blood from leaving the penis. If this mechanism fails, erectile dysfunction may result [76]. Venous ligation is a method of surgery that aims to reinstate the veno-occlusive mechanism, to prevent venous leakage associated with erectile dysfunction [76]. However, while these surgeries were often performed in the past, they have fallen out of popularity due to their lack of long-term efficacy [75].
Penile prosthetic surgery has been around since the 1970s but has undergone several iterations throughout the years. These surgeries continue to be the mainstay of surgical treatment for erectile dysfunction. Among all therapeutic treatments for ED, penile prosthesis have shown the highest satisfaction rates [77]. However, this treatment is reserved for use after other treatment modalities, such as medication, have failed [77].
Currently, there are two major types of penile prosthesis. The first is the inflatable prosthesis, which features two inflatable cylinders, one in each corporal body, as well as a pump and a fluid-filled reservoir. Fluid is pumped from the reservoir and into the inflatable cylinders when erection is warranted [78]. The inflatable prosthesis tends to be the more popular of the two. The second type of prosthesis is termed semirigid. These devices remain firm in the penis but are often very pliable [78]. Both types of prosthesis come in different lengths and girths, and proper sizing based on corporal body size is very important for patient functionality and satisfaction [78].
It is important to note that because of the invasiveness associated with penis prosthesis, oftentimes surgery will result in the development of scar tissue around the prosthesis [3]. Thus, an important consideration for penile prosthesis is that after surgery, pharmacological therapies will no longer be effective, due to the irreversible damage to the erectile bodies [3]. Furthermore, the patient should be informed that surgery often might result in a shortened penis length [79].
Low-intensity extracorporeal shock wave therapy (Li-ESWT) is a new, minimally invasive, experimental ED treatment. Li-ESWT works to improve ED with vasculogenic origin, often seen in diabetic patients [80]. While the exact mechanism of action is not yet known, Li-ESWT acts on the NO/cGMP signaling pathways to increase erectile function [80]. Lei et al. [80] showed that in a rat model with streptozotocin-induced diabetes, Li-ESWT worked to improve erectile function as well as reduce the diabetes-induced pathologic changes occurring in penile tissue. Li-ESWT promoted eNOS phosphorylation and regenerated nNOS-positive nerves, endothelium, and smooth muscle [80]. Since these early reports, several clinical trials have presented encouraging results. Many of these studies showed that Li-ESWT significantly improved the IIEF and EHS, the main questionnaires used to assess the quality of erectile function in ED patients [81]. A recent study showed the ability of Li-ESWT to shift 50 % of PDE5 inhibitor nonresponders into responders, suggesting a possible benefit even in patients with severe nonresponsive ED [82]. Despite encouraging early reports of this minimally invasive therapy, longer follow-up is needed to establish the place of Li-ESWT in patients with ED [82].
Psychosocial Interventions
As stated earlier, there is currently a heavy emphasis within the field of sexual medicine in treating dysfunction using fast-acting pharmaceuticals. However, pharmaceuticals alone may not be adequate to fully treat patients. Not only can the pharmacological route lead to several negative side effects, oftentimes the sexual dysfunction is complex and intricately related to patient’s psychosocial well-being [83]. Sexual dysfunction is often not solely based on biological factors alone, and it is difficult to separate the psychosocial influence on a patient’s sexual dysfunction. Thus, it would be prudent to take a more balanced approach to treatment, utilizing both medication and psychotherapy.
While pharmaceuticals have proven their efficacy in treating sexual dysfunction, it has been found that without a reinforcing form of therapy, rates of premature pharmaceutical discontinuation are much higher in patients [83]. Althof suggests an integrative treatment utilizing both medication and therapy in order to help patients increase the success of their sexual functioning [83]. Furthermore, there are several psychosocial benefits associated with psychotherapy that may be integral to returning sexual functionality. Some of these benefits to the patient include empowerment to create change, increased understanding of the nature of the dysfunction, and the creation of realistic expectations [83].
Mindfulness-based cognitive therapy is being studied further for its efficacy in treating sexual dysfunction. Female sexual desire/arousal disorder (SIAD) is one of the most common sexual dysfunctions in women and one in which pharmaceutical treatment has shown inconsistent efficacy [84]. It has been suggested that an increase in cognitive distraction during sex may be a main contributing factor to SIAD in women [85]. Furthermore, other studies have shown a relation between SIAD and an increased predisposition for anxiety, as well as increased judgmental intrusions [86]. These associated psychosocial symptoms related to SIAD make this dysfunction a particularly good candidate for mindfulness-based sex therapy. This specific type of therapy helps the patient to focus attention on the present moment, cultivating an open, nonjudgmental, accepting awareness [87].
In a recent study conducted by Brotto et al., researchers measured the efficacy of mindfulness-based therapy in the treatment of SIAD by measuring concordance between genital sexual arousal and subjective self-reported sexual arousal. Researchers found an increased concordance between genital arousal and subjective arousal, suggesting that mindfulness-based therapy may result in increased integration between physical and mental sexual responses to erotic stimuli in women [84]. It has also been suggested that mindfulness-based therapy may increase sensitivity to sexual stimuli due to its focus on breathing and thought patterns. This finding was demonstrated in a study that found a decrease in reaction time to sexual stimuli following mindfulness training [88].
Sex therapy is another form of psychotherapy that has shown some treatment efficacy in the field. While sex therapy in general has been around for some time, the approach to treatment has changed quite a bit. Initially, sex therapy focused on what was initially believed to be the goal of sexual intercourse—the orgasm [89]. However, in more recent years, the focus has changed, as practitioners have begun to direct treatment goals toward an increase in pleasure, satisfaction, and desire [90]. Thus, practitioners have moved away from a bottom-line biological response and have instead emphasized much of the psychosocial nature of sexuality.
Recently, there has been a movement toward modifying sex therapy in order to make it more efficient, so as to improve symptoms more quickly with less therapy sessions, thus making it more affordable for patients [90]. One method that incorporates this line of thinking, PLISSIT created by Jack Annon, is often used for both men and women being treated for sexual dysfunction [90]. This treatment aims at quick individualized interventions for treating several sexual dysfunctions. The therapist works to give the patient “permission” for the patient’s sexual activities, fully educating the patient on their “limited” information about sexual functioning and recommending “specific suggestions” to increase functionality [90]. Only when these three modalities fail to improve outcomes is “intensive therapy” initiated to address more underlying causes of dysfunction [90].
There has also been an emphasis on internet-delivered cognitive behavioral therapy (ICBT) that allows patients to perform several self-help treatment exercises from the comfort of their own home [91]. Again, this form of therapy offers a more cost-effective therapeutic treatment for patients in a space that allows them to be comfortable, honest, and fully expressive [92]. A recent study testing the efficacy of ICBT showed significant improvements in erectile function relative to control [91]. ICBT has also been shown to be effective for treating female sexual dysfunction, often incorporating exercises such as sensate focus and communication skills. In one study measuring these effects, 44 % of women are no longer classified as has having sexual dysfunction after completing the ICBT program [93].
Future Direction of Lifestyle Treatments and Complementary Medicine
While general medical practice has long relied heavily on pharmacological methods of treatment, there is an increasing focus on lifestyle modifications in order to arrest or even reverse a wide variety of disease. It is widely accepted that nutritional balance and physical activity can both prevent as well as treat several noncommunicable lifestyle morbidities such as diabetes, heart disease, and hypertension. A combination of nutritional balance and adequate physical activity may play a significant role in the treatment of sexual dysfunction. Special attention has been given to plant-based diets, which continue to prove their efficacy throughout the literature. Currently, researchers in the field of sexual medicine are exploring the possible link between diseases of lifestyle and their relationship to sexual dysfunction. There seems to be strong evidence that adopting healthier lifestyle choices may not only lead to better cardiovascular health but to increased sexual function as well.
One of the most common sexual dysfunctions affecting men globally is erectile dysfunction . In America, over 18 million men are affected [94]. It has long been known that erectile dysfunction is closely related to several lifestyle diseases such as cardiovascular disease and type II diabetes. This is due to the fact that penile erection is highly dependent on the blood flow to the penis. Thus, risk factors such as a high resting heart rate, decreased blood vessel elasticity, and atherosclerosis, can all contribute to the restriction of proper penile perfusion [94].
Diabetic males are at an increasingly high risk for developing erectile dysfunction [95]. Current estimates suggest that by 2025, the prevalence of ED is expected to double [95]. Much of the increased prevalence in ED may parallel a simultaneous spike in type II diabetes. Conducting a study on the comorbidities in men with ED, Kalter-Lebovici et al. found that the longer a patient lived with diabetes, both prevalence and severity of erectile dysfunction increased [95]. Furthermore, a correlation was found between higher A1C values and the severity of ED. The less controlled the patient’s diabetes, the more severe the dysfunction, leading researchers to believe that increased microvascular injury secondary to hyperglycemia may be contributing to decreased perfusion and thus increased severity of dysfunction [95].
For diabetic patients with comorbidity of erectile dysfunction, nutritional intervention may prove to be a powerful treatment choice for both diseases. The latest nutritional research has established that the whole food plant-based diet may be one of the most efficacious lifestyle modifications in the prevention and treatment of diabetes [96]. The development of type II diabetes is thought to be due to increased accumulation of adipose tissue in the body leading to a blockage of insulin receptors and thus increased insulin insensitivity [96]. Thus, individuals with a higher intake of fats will develop increased intramyocellular lipids within their muscle cells, leading to free radical damage of insulin receptors causing insulin resistance [96]. The Adventist Health Study-2, conducted by Fraser et al., assessed BMI as well as the prevalence of diabetes across several different diets. During the study, Fraser assessed nonvegetarians, pesco-vegetarians, lacto-ovo-vegetarians, and vegans. Results found a correlation between diet and BMI, with individuals eating a vegan diet having the lowest average BMI at 23.13.
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