Does peripheral arterial disease only affect old people?

Worse with age. Peripheral arterial disease is when the arteries (the vessels that carry the healthy, oxygenated blood to the tissues), become compromised (narrowed, blocked) and the tissues get less blood flow. This worsens with age due to the cumulative effects of the many factors that affect us (cholesterol, smoking, obesity, lack of activity). As we get older, these get worse and affect us more and more.
No. Risk factors include age over 50 years old, tobacco abuse, diabetes, high blood pressure, prior stroke, prior heart attack.