Why small vessels signal trouble first
Erectile function depends on healthy blood flow through relatively small arteries supplying the penis. Atherosclerosis and endothelial dysfunction, the same processes that eventually narrow the larger coronary and cerebral arteries, tend to affect these smaller vessels earlier in a measurable way. This is the basis of the artery size hypothesis: a fixed amount of plaque obstructs a narrow vessel sooner than a wide one.
Because of this, new erectile dysfunction in a man without an obvious local cause can act as an early marker of generalised vascular disease, often appearing some years before a cardiac event. Reported lead times vary across studies and individuals, so any single figure is an average rather than a rule.
What the association does and does not mean
The link is an association and a prompt for assessment, not a diagnosis of heart disease in itself. Erectile dysfunction also has neurological, hormonal, psychological, and medication-related causes that are unrelated to the vasculature, so context matters.
This is general educational information, not medical advice. New or persistent erectile dysfunction is worth discussing with a clinician, who may consider cardiovascular risk as part of the picture.