Erectile dysfunction is one of the most common reasons men in their 40s and 50s come to see a doctor — and one of the most delayed. The average time between first noticing a problem and seeking help is measured in years, not weeks. By the time most men do come in, they’ve either convinced themselves it will resolve on its own, or they’ve arrived hoping for a prescription.
The prescription conversation is worth having. But it should come after a more fundamental one: what is actually causing this? Erectile dysfunction is a symptom, not a diagnosis. The causes are varied, often overlapping, and in many cases point to something in the underlying health picture that deserves attention in its own right. Understanding what’s driving the problem determines both how to treat it and what else to look at.
This article explains the main causes of erectile dysfunction, how they differ, and what a proper assessment involves. A companion article covers the specific link between erectile dysfunction and cardiovascular health in more detail.
How common is erectile dysfunction in Singapore?
More common than most men realise, and more common than most men discuss. The landmark population-based study on erectile dysfunction in Singapore — conducted with 729 men aged 30 and above and published in the Singapore Medical Journal in 2003, found that 51.3% reported some degree of erectile dysfunction.[1] Prevalence increased significantly with age: 42.8% of men in their 40s were affected, rising to 77.4% of men in their 60s. Severe erectile dysfunction — defined as an IIEF-5 score below 11 — affected 9.1% of men in their 40s, climbing to 43.5% in their 60s and 77.0% in those aged 70 and above.[1]
The study identified the key independent risk factors beyond age: diabetes mellitus, cardiac disease, physical inactivity, and lower household income.[1] These associations are not incidental. They reflect the shared biological mechanisms that connect erectile function to overall metabolic and vascular health — the point the rest of this article builds on.
One finding worth noting: younger Singapore men showed higher rates than expected, a pattern also seen in international data. A 2024 review in the Singapore Medical Journal on erectile dysfunction assessment and management in primary care confirmed that the condition is increasingly presenting in men under 40 — and that organic, not purely psychological, causes are being identified in a substantial proportion of them.[2]
The figures suggest that if you have ED, you are far from alone — and far from unusual in not having discussed it with a doctor yet. That conversation is the part most men find harder than the treatment itself.
What needs to work for an erection to happen
An erection depends on the coordinated function of three systems: the vascular system (adequate blood flow into the penis and maintained there), the nervous system (signals from the brain and local nerve pathways), and the hormonal system (testosterone and related hormones driving libido and supporting vascular function). A problem with any one of these — or a combination — can produce erectile dysfunction.
The mechanism at the cellular level involves nitric oxide, which is released during sexual arousal from nerve endings and the endothelial lining of penile blood vessels. Nitric oxide triggers a cascade that relaxes smooth muscle in the corpus cavernosum, allowing blood to flow in and the erection to develop and be maintained.[3] This is also why endothelial health — the health of the blood vessel lining — is so central to erectile function, and why conditions that damage the endothelium (diabetes, hypertension, smoking, elevated cholesterol) are consistently associated with erectile dysfunction.
The main causes — and how to tell them apart
Vascular causes
The most common cause of erectile dysfunction in men over 40 is vascular: reduced blood flow to the penis due to atherosclerosis and endothelial dysfunction. The same process that narrows coronary arteries narrows penile arteries, and because penile arteries are smaller in diameter, the effect often shows up earlier in sexual function than in cardiac symptoms.[4]
Vasculogenic erectile dysfunction tends to develop gradually. A man notices that erections are less firm, take longer to develop, or are more difficult to maintain — particularly under conditions of fatigue or stress. Morning erections may reduce in frequency or firmness over time. The progression is typically slow, over months to years.
The risk factors for vasculogenic erectile dysfunction are the standard cardiovascular risk factors: smoking, hypertension, dyslipidaemia, diabetes, obesity, physical inactivity, and age. Importantly, erectile dysfunction may appear before any cardiac symptoms are noticed, precisely because penile arteries are more vulnerable to early vascular disease. A 2014 systematic review in European Urology concluded that erectile dysfunction can be used as an early marker to identify men at higher risk of cardiovascular events, and that patients with erectile dysfunction at high cardiovascular risk should undergo detailed cardiological assessment.[4]
Vasculogenic ED can also occur in younger patients (< 40 years old) without any cardiovascular risk factors. This form of vasculogenic ED manifests as a venous leak due to loose blood vessels in the testicles forming a negative pressure sink that draws blood that is supposed to go to the penis (for an erection) down into the scrotum. The cause of such loose blood vessels termed varicoceles is genetic and can occur at any age. Patients tend to notice a venous leak when they find that their erections are better in certain positions (usually lying down) and decreases distinctly when they change positions (usually to a standing position).
Psychological causes
Psychological erectile dysfunction is real, clinically distinct, and often misdiagnosed in both directions — men with organic causes are sometimes told it’s “just stress,” and men with genuine psychological causes are sometimes given medication when the underlying issue is performance anxiety or relationship distress.
Psychogenic erectile dysfunction is more common in younger men. Historically it was assumed to account for the majority of erectile dysfunction in men under 40, but this picture has been revised: studies have identified organic etiologies — including vascular, neurogenic, endocrine and medication-related causes — in 15 to 72% of younger men presenting with erectile dysfunction.[5] It is now understood as a multidimensional condition with organic and psychological components that frequently coexist.[6]
The clinical features that suggest a predominantly psychological cause include: sudden onset rather than gradual; situational occurrence (with some partners but not others, or in some situations but not others); preserved spontaneous or morning erections; and a clear temporal link to a stressful period or relationship difficulty. The presence of consistent morning erections is particularly relevant — it suggests the vascular and neurological machinery is functioning and the issue is more likely psychogenic.
Psychogenic ED is often the most frustrating form of ED because these patients tend to try everything to fix the problem only to be told that it is all in their head. Worse still, because the penis is a muscle and like any muscle in the body, the less you use it the faster you lose it. In the context of erections, it means that the fewer erections you have the weaker your penile muscles become and hence over time it will become harder to achieve an erection.
Hormonal causes
Low testosterone — hypogonadism — can contribute to erectile dysfunction through several mechanisms: reduced libido, reduced nitric oxide production in penile tissue, and changes in mood and energy that affect sexual engagement. However, it is rarely the sole cause of erectile dysfunction. Most men with low testosterone also have vascular or other organic contributors, and treating the testosterone without addressing these gives an incomplete result.
Thyroid disorders and elevated prolactin are less common hormonal causes and are worth checking in men who present with low libido and fatigue alongside erectile dysfunction, particularly if the clinical picture doesn’t fit the standard vascular or psychological profile.
Neurological causes
The nervous system plays a central role in initiating and maintaining erections. Neurological causes of erectile dysfunction include: diabetes-related autonomic neuropathy, spinal cord injury from traffic accidents or sports injuries or disease, pelvic nerve damage from prostate surgery, radiotherapy or long hours of cycling, and neurological conditions such as multiple sclerosis. Medication side effects — particularly antidepressants, antihypertensives, and anti-androgens — can also impair erectile function through central and peripheral nervous system pathways.
A careful medication review is part of every erectile dysfunction assessment. Several widely-used drugs affect sexual function, and a dose adjustment or switch to an alternative agent is sometimes all that is needed.
Knowing what is causing your ED changes what the treatment looks like. Self-treating without that clarity — with supplements, devices, or pills from unverified sources — is a different and considerably less effective path.
What a proper assessment involves
Vascular causes
A prescription for a PDE5 inhibitor — sildenafil or tadalafil — is not an assessment. It is a treatment that addresses the symptom, and a useful one in many cases. But it should not be the first and only step, particularly in a man who has never had his cardiovascular and metabolic health properly evaluated.
A proper assessment begins with a thorough history. The pattern of onset (gradual vs sudden), the circumstances in which erectile dysfunction occurs, the presence or absence of morning erections, libido, previous medical conditions, medications, and lifestyle factors all shape the clinical picture before a single test is ordered.
Physical examination includes blood pressure (hypertension is both a cause and a compounding factor in erectile dysfunction), and assessment of secondary sexual characteristics where hypogonadism is a possibility.
Blood testing in a man presenting with erectile dysfunction typically includes: fasting glucose and HbA1c (to assess for diabetes or pre-diabetes), lipid profile, testosterone (total and, where indicated, free), and thyroid function where clinically suggested. These are not optional add-ons. They are the investigations that determine whether the erectile dysfunction is an isolated problem or part of a broader metabolic and vascular picture — and that picture often changes the treatment plan.
Key principle: Erectile dysfunction in a man who has never had a metabolic and cardiovascular workup is an opportunity to do that workup, not just to treat the symptom.
A proper assessment for ED is not a lengthy or uncomfortable process. It involves a history, a physical examination where relevant, and targeted blood tests. Most men find it considerably more straightforward than they expected.
Treatment: a hierarchy, not a menu
The treatment of erectile dysfunction is most effective when it is matched to the cause. Understanding this hierarchy matters: treating the symptom is not the same as treating the underlying problem.
Addressing underlying causes and risk factors
In vasculogenic erectile dysfunction, the most impactful long-term intervention is reducing the cardiovascular risk factors driving the vascular damage. Smoking cessation, blood pressure control, treatment of dyslipidaemia, glycaemic management in diabetes, weight loss, and structured exercise have all been shown to improve erectile function — not as indirect side-effects, but as direct outcomes of improved vascular and endothelial health. These are the interventions that treat the cause, not just the symptom.
PDE5 inhibitors
PDE5 inhibitors — sildenafil, tadalafil, avanafil, vardenafil and others — are the first-line pharmacological treatment for erectile dysfunction and the most evidence-based option across all cause types.[3] They work by blocking the enzyme (phosphodiesterase type 5) that breaks down cyclic GMP in the smooth muscle of the corpus cavernosum, thereby sustaining the nitric oxide-mediated relaxation that allows blood flow in. They are effective across vasculogenic, psychological, and mixed-cause erectile dysfunction.
An important clinical nuance: PDE5 inhibitors amplify the nitric oxide signal generated by sexual arousal. They do not create arousal, and they do not work in the complete absence of nitric oxide — which is why they are less effective in severe diabetic neuropathy or after radical prostatectomy, where the nerve supply to the penis may be significantly compromised.[7] The choice between agents (on-demand vs daily dosing, duration of action, side effect profile) is a clinical conversation, not a patient preference form.
Prostaglandins
Prostaglandins are a class of medications known as vasodilators that create erections by directly opening up the blood vessels in the penis without needing to go through the Nitric Oxide pathway. They are hence more effective in patients with severe nerve damage/ neurological ED but can also be used in any ED patient. The one limitation to the prostaglandins is that the medication needs to be administered directly to the penis either with an injection or a cream. The most common prostaglandin is Alprostadil and this can be further enhanced with adjuvant medication which is known as Tri-Mix containing Papaverine, Phentolamine and Alprostadil.
Low-intensity shockwave therapy
Low-intensity shockwave therapy (Li-ESWT) is a non-pharmacological treatment for vasculogenic erectile dysfunction delivered in a series of clinic sessions. It works through neovascularisation — stimulating new blood vessel growth in penile tissue — rather than symptom management.
The evidence base has strengthened considerably. A 2026 systematic review and meta-analysis of 19 randomised controlled trials in the Journal of Sexual Medicine found statistically significant improvements in erectile function scores with shockwave therapy compared to sham treatment, particularly in men with mild to moderate vasculogenic erectile dysfunction.[8] A 2024 umbrella review in the Journal of Personalised Medicine, covering five systematic reviews and meta-analyses, reached similar conclusions.[9] The therapy is appropriate for selected patients and is most effective in men with mild to moderate vasculogenic erectile dysfunction who respond inadequately to PDE5 inhibitors, or who prefer a non-pharmacological approach.
Psychological support
Where the clinical picture suggests a significant psychological component — performance anxiety, relationship distress, depression — addressing this directly produces better outcomes than medication alone. For men with purely psychogenic erectile dysfunction, sex therapy or cognitive behavioural therapy is often more appropriate than pharmacotherapy as a first step. For men with mixed causes, both may be needed concurrently.
In 2021, the European Society for Sexual Medicine did find that later onset of first sexual experience to be one of the risk factors for psychogenic ED. A further problem to this observation is that by having sexual intercourse at a later stage in life, men are not able to become attuned to their body and understand which muscles need to be engaged during intercourse. Therefore, improving the body awareness and specific exercises can help improve the overall confidence of the patient and reverse psychogenic ED.
Hormone treatment
Where low testosterone is confirmed as a contributing factor, testosterone replacement therapy may be appropriate — but this requires accurate diagnosis, a full hormonal assessment, and a careful discussion of the risks, benefits, and monitoring requirements. Testosterone therapy in a man with normal testosterone levels is not an effective treatment for erectile dysfunction.
The treatments for ED are more varied than most men realise, and the right one depends on the cause. The right treatment for ED depends on the right diagnosis. Starting with a pill is not wrong — but starting with a proper assessment first means the pill is actually part of the right treatment plan rather than a guess. A brief consultation establishes that cause. Everything useful follows from there.
The practical point
Erectile dysfunction is common, it is treatable, and it is often a window into aspects of a man’s health that would otherwise go unexamined. The men who benefit most from assessment are not necessarily those with the most severe symptoms — they are those who come in early enough for the underlying picture to be mapped and addressed before it progresses.
The question worth asking is not only “how do I treat this?” but “what is this telling me?” The answer is frequently more useful than the prescription it leads to.
ED is common, well-understood, and treatable in most cases. If it is something you have been putting off addressing, the consultation is shorter and more straightforward than most men expect. The first step is the conversation with your doctor.
- Tan JK, Hong CY, Png DJ, Liew LC, Wong ML. Erectile dysfunction in Singapore: prevalence and its associated factors — a population-based study. Singapore Med J. 2003;44(1):20–6. PMID: 12762559.
- Ong YN, Tan YG, Handayani D, How CH. Erectile dysfunction: assessment and management in primary care. Singapore Med J. 2024;65(3):190–194. doi:10.4103/singaporemedj.SMJ-2022-101. PMC: PMID 38527306.
- Huang SA, Lie JD. Phosphodiesterase-5 (PDE5) inhibitors in the management of erectile dysfunction. P T. 2013;38(7):407–419. PMC3776492.
- Gandaglia G, Briganti A, Jackson G, et al. A systematic review of the association between erectile dysfunction and cardiovascular disease. Eur Urol. 2014;65(5):968–978. PMID: 24011423.
- Tal R, Alphs HH, Krebs P, Nelson CJ, Mulhall JP. Organic causes of erectile dysfunction in men under 40. Urol Int. 2014;92(1):1–6. PMID: 24281298.
- Safa A, Waked C. Erectile dysfunction in young adults: a narrative review. Cureus. 2025 Aug;17(8):e89918. PMC12349891.
- Burnett AL, et al. Nitric oxide in the penis: physiology and pathology. J Urol. 1997.
- Lapauw LM, et al. A close look at the evidence on low-intensity shockwave therapy in erectile dysfunction — a systematic review and meta-analysis of randomized controlled trials. J Sex Med. 2026;23(4):qdag070. doi:10.1093/jsxmed/qdag070.
- Rubío-Arias M, et al. Effectiveness of low-intensity extracorporeal shock wave therapy in erectile dysfunction: an analysis of sexual function and penile hardness at erection: an umbrella review. J Pers Med. 2024;14(2):177. doi:10.3390/jpm14020177.