#1.) Smoking. Smoking damages your blood vessels, which can make less blood flow down below.

#2.) Erectile dysfunction. This adds insult to injury for guys with ED. Without regular erections, your
tissue down below becomes less elastic. And that can knock off almost a FULL INCH of size over time.

#3.) Getting older. By the time you're in your 60s, you start losing length AND girth. You can drop half an inch to an inch by the time you're 60, and even more after that.

WebMD