This may occur as people age, but high blood pressure accelerates this process, probably because hypertension speeds atherosclerosis. Arterial damage is bad because hardened or narrowed arteries may be unable to supply the amount of blood the body's organs need. And if the body's organs don't get enough oxygen and nutrients, they can't function properly. There's also the risk that a blood clot may lodge in an artery narrowed by atherosclerosis, depriving part of the body of its normal blood supply. The heart, brain and kidneys are especially prone to damage by high blood pressure.
High levels are a large factor in clogging arteries.
Your blood pressure is also checked each time you donate.