A review in Medical News Toady Nov 2007 has the following title:
Researchers Show That Veins Stiffen As We Age.
It has the following quote "Hardening of the arteries is a good analogy for what is happening in our veins as we grow older."
Wonder if people very low on vitamin D - elderly, MS, Crohn's, obese, chemotherapy, cystic fibrosis, liver or kidney malfunction, far from equator, etc are "difficult sticks", due to their veins being too hard?
Realize that the main problem for blood draws is finding a vein, not vein stiffness.