I started my PN when I was about 30. It was due to hypothyroid issues. Once that was fixed my feet came back to 90% normal.

But we do see younger people here now, than say back a decade when I started online.

Younger means aging is not the simple culprit. Many autoimmune diseases are showing up in younger people now, because of the extreme push vaccines are being given. The H1N1 vaccine in other countries had squalene in it and this has been shown in animals to stimulate autoimmune reactions. We have a Canadian poster here who got 2 doses by mistake, and had nerve damage from it. In Australia, the H1N1 vaccine caused seizures in infants, and was discontinued for a time.
In northern Europe, there is now a cluster of narcolepsy in children being found who received the vaccine.

People are being exposed to things nowadays that we weren't in the past, so yes, younger ages. Diabetes type II is now occurring in late teens in the US! So the neuropathy that comes from that would be showing up younger. I've seen some healthy men of normal weight showing up with type II in their 30's.

So while 40ish is not terribly young anymore, it is still less likely for PN compared to the past, where PN was mostly in older folks. When the teens and 20's posters show up, I suspect
mostly vaccine injury or drug injury.

The drug thread can be helpful because there are MANY drugs including common ones that can actually cause PN:
http://neurotalk.psychcentral.com/thread122889.html

On some lists is an antibiotic no longer available here and in most countries. BUT...I have discovered that SHRIMP farmed in Thailand and some other places have chloramphenicol added to them, and we may be exposed to that by just eating shrimp in restaurants and at home! Something I love to do!
So PN can be very sneaky and get you even when you are thinking you are doing all you can to avoid it.

http://www.cbsnews.com/2100-500262_162-644203.html
I was having shrimp a couple of times a month, and when I went out... I am now concerned!