簡潔的答案：無人知曉。

詳細解釋：如果不是不可能的話，要估計多少人罹患性功能障礙及其患病程度是困難的。性治療師或欲出售其服務或產品的藥業公司提供了可資利用的大多數資料，並且由此推斷從大量潛在病人那裏有著專業營業利潤。不管怎麼說，去進行性治療的病人決不會代表著整個病人的數量。真正具有代表性的性調查是罕見的，即使有調查結果也通常無據可考，因為自我承認的性障礙是不可靠的。許多人就性的問題上會說謊，要麼會否認自己有病，要麼會誇大自己的病情。至於還有的人，由於沒有意識到自身生活中與生物學相關的和社會環境的現實影響，他們在對待性行為方面固守著那些不切實際的性準則。此外，就像我們始終所陳述的那樣，性功能障礙本身的任何定義不得不是一個“具有彈性的指標”和並不精確。這個術語本身會不斷地延伸其概念，並且過去常常習慣於包括性問題上的所有類型的輕度不適和暫時的困擾。然而，人非機器，每一個人在進行性活動時可能體驗過這樣的情形：“心神嚮往，卻身不由己(spirit is willing, but the flesh is weak)”。對於這樣的情形，把其診斷為性功能障礙顯然是不合適的。最後要指明的是，不同的人有著不同的性需要，那麼某些性伴在各自的性需要上也許非常的不相配。與不同的性伴在一起，他們可能根本就沒有任何的性障礙。簡而言之：
對任何所宣稱的性功能障礙的流行病統計資料要保持清醒的頭腦！

Short answer: Nobody knows.

Long answer: It is difficult, if not impossible, to say how many people suffer from sexual dysfunctions and to what degree. Most available figures are provided by therapists or drug companies who want to sell their services or products and thus have a professional interest in large numbers of potential patients. In any case, patients showing up for therapy are never representative of the populations as a whole. Truly representative sex surveys are rare and usually silent on this point, because self-reports about sexual difficulties are not reliable. Many people lie, deceive themselves or exaggerate in either direction. Others, being unaware of the biological and social realities around them, cling to unrealistic norms of sexual performance. Moreover, as already stated, any definition of sexual dysfunction itself cannot help but be "soft" and imprecise. The term lends itself to stretching and often is used to cover all kinds of minor disappointments and temporary inconveniences. However, people are not machines, and everyone is likely to experience occasions when the "spirit is willing, but the flesh is weak". In such cases, it would be inappropriate to speak of a sexual dysfunction. Finally, different people have different sexual needs, and some couples may be greatly mismatched in this regard. With different partners they might not have any problems at all. In short:
Beware of any number about the alleged prevalence of sexual dysfunctions!