Why are finasteride sexual side effects mostly reported in older men?

Pretty much all of the original fin studies looked at men who were like 55, or 62. When you look at 55 or 62 year olds, over half of them have ED and low libido due to atherosclerosis and dropping hormones, so no wonder they wouldn’t notice a difference with fin.

That is because the drug finasteride (Proscar) was first developed for prostate problems and that doesn’t occur in men under 55 years old as a general rule. Erectile Dysfunction (ED) is relatively common in men over 55 with a frequency as high as 50% of men, so if these men take finasteride (Proscar which has 5mgs of finasteride in it for prostate hypertrophy), then their ED is reported in the studies of these men.