We once thought that atherosclerosis is an old persons disease, where health habits later in life lead are what predicates plaque formation. The Army started noticing fatty streak formation(first stage of atherosclerosis)[2] in arteries of dead soldiers during autopsy, which now leads us to believe this starts in youth and progresses from there.
1) https://www.ingentaconnect.com/content/ben/vdp/2005/00000002...
2) https://media.jamanetwork.com/news-item/autopsy-based-study-...