Loaded question. That is a loaded question, however of course the easiest answer is that it is commonly thought to be caused by things like "bad" genes, high blood pressure, dense particles of cholesterol, and finally perhaps the most important one, inflammation. More and more people are discovering that the underlying reason appears to be an inflammatory process.
Risk factors. Risk factors for arteriosclerosis include: age greater than 40 yo in men and postmenopausal in women, men more likely than women, hypertension, diabetes, tobaco, obesity, sedentary life style, family history.Others like high levels of inflamation and high homocystiene levels less well defined.These are riskfactors or markers no one cause has been implicated and we treat and modify all we can .